Shafts and axles
Plan 1. Appointment. 2. Classification. 3. Structural elements of shafts and axles. 4. Materials and heat treatment. 5. Calculations of shafts and axles.
Purpose
Shafts - parts designed to transmit torque along their axis and to support rotating machine parts. The shaft perceives the forces acting on the parts and transfers them to the supports. During operation, the shaft experiences bending and torsion.
axes designed to support rotating parts, they do not transmit useful torque. The axles do not experience torsion. Axes can be fixed and rotating.
Shaft classification
By appointment:
a) gear shafts, bearing gear parts - couplings, gears, pulleys, sprockets;
b) main shafts of machines;
c) other special shafts carrying the working bodies of machines or tools - wheels or turbine disks, cranks, tools, etc.
By design and form:
a) straight lines;
b) cranked;
c) flexible.
Straight shafts are divided into:
a) smooth cylindrical;
b) stepped;
c) shafts - gears, shafts - worms;
d) flanged;
e) cardan.
According to the shape of the cross section:
a) smooth solid section;
b) hollow (to accommodate the coaxial shaft, control parts, oil supply, cooling);
c) slotted.
Axes are divided into rotating, providing best work bearings, and stationary, requiring the integration of bearings into rotating parts,
Structural elements of shafts and axles
The supporting part of a shaft or axle is called trunnion. The end cap is called thorn, and the intermediate neck.
The annular thickening of the shaft, which is one with it, is called bead. The transitional surface from one section to another, which serves to stop the parts mounted on the shaft, is called shoulder.
To reduce concentration and increase strength, transitions in places where the diameter of the shaft or axis changes are made smooth. The curved surface of a smooth transition from a smaller section to a larger one is called fillet. Fillets are of constant and variable curvature. The variability of the radius of curvature of the fillet increases the bearing capacity of the shaft by 10%. Fillets with inner lining increase the length of the hubs.
Increasing the strength of the shafts in the transition sections is also achieved by removing low-stress material: making relief grooves and drilling holes in large diameter steps. These measures provide a more uniform distribution of stresses and reduce the concentration of stresses.
The shape of the shaft along the length is determined by the distribution of loads, i.e. bending and torque diagrams, assembly conditions and manufacturing technology. The transition sections of the shafts between steps of different diameters are often made with a semicircular groove for the output of the grinding wheel.
The landing ends of the shafts, designed to install parts that transmit torque in machines, mechanisms, devices are standardized. GOST establishes the nominal dimensions of cylindrical shafts of two designs (long and short) with diameters from 0.8 to 630 mm, as well as the recommended sizes of threaded shaft ends. GOST establishes the main dimensions of the conical ends of shafts with a taper of 1:10, also of two versions (long and short) and two types (with external and internal threads) of diameters from 3 to 630 mm.
"Highlanders shafts to facilitate fitting parts, in order to avoid crumpling and damage to the hands of workers, they are chamfered.
Materials and heat treatment
Material selection and heat treatment shafts and axles is determined by the criteria for their performance.
The main materials for shafts and axles are carbon and alloy steels due to their high mechanical characteristics, the ability to harden and the ease of obtaining cylindrical billets by rolling.
For most shafts, medium-carbon and alloy steels 45, 40X are used. For high-stress shafts of critical machines, alloyed steels 40KhN, 40KhNGMA, 30KhGT, 30KhGSA, etc. are used. Shafts made of these steels are usually subjected to improvement, hardening with high tempering or surface hardening with high-frequency heating and low tempering.
For the manufacture of shaped shafts - crankshafts, with large flanges and holes - and heavy shafts, along with steel, ductile irons (with nodular graphite) and modified cast irons are used.
Calculation of shafts and axles
Shafts are subjected to bending and torsion stresses, while axles are only subjected to bending.
During operation, the shafts experience significant loads, therefore, in order to determine the optimal geometric dimensions, it is necessary to perform a set of calculations, including the determination of:
Static strength;
fatigue strength;
Rigidity in bending and torsion.
At high speeds rotation, it is necessary to determine the natural frequencies of the shaft in order to prevent falling into the resonant zones. Long shafts are checked for stability.
Shafts are calculated in several stages.
To perform the calculation of the shaft, it is necessary to know its design (places of load application, location of supports, etc.). At the same time, the development of the shaft design is impossible without at least an approximate assessment of its diameter. In practice, the following procedure for calculating the shaft is usually used:
1. Preliminarily estimate the average diameter based on torsion only at reduced allowable stresses (the bending moment is not yet known, since the location of the supports and the places where the loads are applied are unknown).
Torsional stress
Where Wp is the section modulus, mm.
You can also preliminarily estimate the shaft diameter based on the diameter of the shaft with which it is connected (the shafts transmit the same moment T). For example, if the shaft is connected to the shaft of an electric motor (or other machine), then the diameter of its input end can be taken equal to or close to the diameter of the output end of the motor shaft.
2.Basic calculation of the shaft.
After evaluating the shaft diameter, its design is developed. The length of the shaft sections, and, consequently, the shoulder of the application of force, we take from the layout. Suppose we need to calculate the diameter of the shaft on which the helical gear sits. Let's draw a diagram of the shaft loads. For this shaft, taking into account the inclination of the gear teeth and the direction of the moment T, we replace the left support with a hinge-fixed one, and the right one with a hinge-movable one. The design loads are usually considered as concentrated, although the actual loads are not concentrated, they are distributed along the length of the hub, the width of the bearing. In our example, the shaft is loaded with forces Ft, Fa. Fr, acting in the pole of engagement and torque T. The axial force Fa gives the moment in the vertical planeThe main calculation of shafts and axes consists in plotting curves of bending moments in the horizontal and vertical planes, plotting resulting moments, plots of torques, plots of equivalent moments, and determining dangerous sections.
3rd stage of calculation- verification calculation consists in determining the safety factor in dangerous sections
- safety factors for normal and shear stresses
endurance limits of materials.- effective stress concentration factors.
- scale factor (depends on the shaft diameter).
- hardening coefficient. - coefficients of sensitivity of the material, depend on mechanical characteristics.- variable stress components.
- constant components of stresses.
Stiffness calculation
Deflection of axles and shafts adversely affects the operation of bearings and gear meshing. Rigidity is characterized by the maximum angle of rotation of the axis or shaft
and deflection The necessary rigidity is ensured if the actual values and do not exceed the allowed limits. At large angles of rotation in plain bearings, the shaft is pinched (especially with a large length of the bearing and pin), and in rolling bearings, the separator may collapse. Large deflections worsen the working conditions of gears (especially with an asymmetrical gear arrangement).Permissible angles of rotation under the pinion [
Before you figure out how the shaft and axle differ from each other, you should have a clear idea of what these parts actually are, what and where they are used for and what functions they perform. So, as you know, shafts and axles are designed to hold rotating parts on them.
Definition
Shaft- this is a part of the mechanism that has the shape of a rod and serves to transfer torque to other parts of this mechanism, thereby creating a general rotational movement of all parts located on it (on the shaft): pulleys, eccentrics, wheels, etc.
Axis- this is a part of the mechanism, designed to connect and fasten the parts of this mechanism together. The axis takes only transverse loads (bending stress). Axes are fixed and rotating.
Axis Comparison
The main difference between an axle and a shaft is that the axle does not transfer torque to other parts. It is only affected by transverse loads and does not experience torsion forces.
The shaft, unlike the axis, transmits a useful torque to the parts that are fixed to it. In addition, the axes are both rotating and fixed. The shaft is always rotating. Most shafts can be divided according to the geometric shape of the axis into straight, crank (eccentric) and flexible. There are also crankshafts or indirect ones, which serve to convert reciprocating movements into rotational ones. The axes, in their geometric form, are only straight lines.
Findings site
- The axle carries the rotating parts of the mechanism without transmitting any torque to them. The shaft transmits a useful torque, the so-called rotating force, to other parts of the mechanism.
- The axis can be either rotating or stationary. The shaft is only rotating.
- The axis has only a straight line. The shape of the shaft can be straight, indirect (crankshaft), eccentric and flexible.
1.1 Service purpose and technical characteristics of the part
To create a quality technological process manufacturing a part, it is necessary to carefully study its design and purpose in the machine.
The part is a cylindrical axis. Most high requirements to the accuracy of shape and location, as well as roughness, are applied to the surfaces of the journals of the axle, intended for fitting bearings. So the accuracy of the necks for bearings must correspond to the 7th grade. High requirements for the accuracy of the location of these axle journals relative to each other follow from the operating conditions of the axle.
All axle journals are surfaces of rotation of relatively high precision. This determines the expediency of using turning operations only for their preliminary processing, and the final processing in order to ensure the specified dimensional accuracy and surface roughness should be performed by grinding. To ensure high requirements for the accuracy of the location of the axle journals, their final processing must be carried out in one setup or, in extreme cases, on the same bases.
Axes of this design are widely used in mechanical engineering.
Axes are designed to transmit torque and mount various parts and mechanisms on them. They are a combination of smooth landing and non-landing surfaces, as well as transitional surfaces.
The technical requirements for the axles are characterized by the following data. The diametrical dimensions of the landing necks are performed according to IT7, IT6, other necks according to IT10, IT11.
The design of the axle, its dimensions and rigidity, technical requirements, production program are the main factors that determine the manufacturing technology and the equipment used.
The part is a body of revolution and consists of simple structural elements, presented in the form of bodies of revolution of a circular cross section of various diameters and lengths. There is a thread on the axle. The axis length is 112 mm, the maximum diameter is 75 mm, and the minimum diameter is 20 mm.
Based on the design purpose of the part in the machine, all surfaces of this part can be divided into 2 groups:
main or working surfaces;
free or non-working surfaces.
Almost all surfaces of the axis are considered basic because they are mated with the corresponding surfaces of other machine parts or are directly involved in the working process of the machine. This explains the rather high requirements for the accuracy of the part processing and the degree of roughness indicated in the drawing.
It can be noted that the design of the part fully meets its official purpose. But the principle of manufacturability of the design is not only to meet the operational requirements, but also the requirements of the most rational and economical manufacture of the product.
The part has surfaces that are easily accessible for processing; sufficient rigidity of the part allows it to be processed on machines with the most productive cutting conditions. This part is technologically advanced, as it contains simple surface profiles, its processing does not require specially designed fixtures and machines. The surfaces of the axis are processed on turning, drilling and grinding machines. The required dimensional accuracy and surface roughness are achieved by a relatively small set of simple operations, as well as a set of standard cutters and grinding wheels.
The manufacture of a part is labor-intensive, which is associated primarily with the provision specifications the work of the part, the necessary dimensional accuracy, the roughness of the working surfaces.
So, the part is manufacturable in terms of design and processing methods.
The material from which the axle is made, steel 45 belongs to the group of medium carbon structural steels. It is used for medium-loaded parts operating at low speeds and medium specific pressures.
The chemical composition of this material is summarized in Table 1.1.
Table 1.1
| 7 | ||||||||
| FROM | Si | Mn | Cr | S | P | Cu | Ni | As |
| 0,42-05 | 0,17-0,37 | 0,5-0,8 | 0,25 | 0,04 | 0,035 | 0,25 | 0,25 | 0,08 |
Let us dwell a little on the mechanical properties of rolled products and forgings necessary for further analysis, which we will also summarize in Table 1.2.
Table 1.2
Here are some technological properties.
The temperature of the beginning of forging is 1280 °C, the end of forging is 750 °C.
This steel has limited weldability
Machinability - in the hot-rolled state at HB 144-156 and σ B = 510 MPa.
1.2 Determining the type of production and batch size of the part
In the task for the course project, the annual program for the production of a product in the amount of 7000 pieces is indicated. According to the source formula, we determine the annual program for the production of parts in pieces, taking into account spare parts and possible losses:
where P is the annual program for the production of products, pieces;
P 1 - annual program for the manufacture of parts, pcs. (accept 8000 pieces);
b - the number of additionally manufactured parts for spare parts and to compensate for possible losses, in percent. You can take b=5-7;
m - the number of parts of this item in the product (accept 1 pc.).
PCS.
The size production program in natural quantitative terms determines the type of production and has a decisive influence on the nature of the construction of the technological process, on the choice of equipment and tooling, on the organization of production.
In mechanical engineering, there are three main types of production:
Single or individual production;
Mass production;
Mass production.
Based on the release program, it can be concluded that in this case We have mass production. At serial production products are manufactured in batches, or in series, periodically repeating.
Depending on the size of batches or series, there are three types of mass production for medium-sized machines:
Small-scale production with the number of products in a series of up to 25 pieces;
Medium-scale production with the number of products in a series of 25-200 pieces;
Large-scale production with the number of products in a series of more than 200 pieces;
A characteristic feature of serial production is that the production of products is carried out in batches. The number of parts in a batch for simultaneous launch can be determined using the following simplified formula:
where N is the number of blanks in the batch;
P - annual program for the manufacture of parts, pieces;
L is the number of days for which it is necessary to have a stock of parts in stock to ensure assembly (we accept L = 10);
F is the number of working days in a year. You can take F=240.
PCS.
Knowing the annual output of parts, we determine that this production refers to large-scale production (5000 - 50000 pieces).
In serial production, each operation of the technological process is assigned to a specific workplace. At most workplaces, several operations are performed, periodically repeated.
1.3 Selecting the way to obtain the workpiece
The method of obtaining the initial blanks of machine parts is determined by the design of the part, the volume of output and the production plan, as well as the economics of manufacturing. Initially, from the whole variety of methods for obtaining initial workpieces, several methods are selected that technologically provide the possibility of obtaining a workpiece of a given part and allow the configuration of the initial workpiece to be as close as possible to the configuration of the finished part. To choose a workpiece means to choose a method for obtaining it, outline allowances for processing each surface, calculate dimensions and indicate tolerances for manufacturing inaccuracies.
The main thing when choosing a workpiece is to ensure the specified quality of the finished part at its minimum cost.
The correct decision on the choice of workpieces, if from the point of view technical requirements and possibilities, their various types are applicable, can only be obtained as a result of technical and economic calculations by comparing the options for the cost of the finished part for one or another type of workpiece. Technological processes for obtaining blanks are determined by the technological properties of the material, the structural shapes and sizes of parts, and the production program. Preference should be given to a workpiece characterized by best use metal and lower cost.
Let's take two methods for obtaining blanks and after analyzing each we will choose the desired method for obtaining blanks:
1) receiving a blank from a rolled product
2) obtaining a workpiece by stamping.
You should choose the most "successful" method for obtaining the workpiece by analytical calculation. Let's compare the options for the minimum value of the reduced costs for the manufacture of the part.
If the workpiece is made from rolled products, then the cost of the workpiece is determined by the weight of the rolled product required to manufacture the part and the weight of the chips. The cost of a rolled billet is determined by the following formula:
,
where Q is the mass of the workpiece, kg;
S is the price of 1 kg of workpiece material, rub.;
q is the mass of the finished part, kg;
Q = 3.78 kg; S = 115 rubles; q = 0.8 kg; S out \u003d 14.4 kg.
Substitute the initial data in the formula:
Consider the option of obtaining a workpiece by stamping on the GCF. The cost of the workpiece is determined by the expression:
Where C i is the price of one ton of stampings, rub.;
K T - coefficient depending on the accuracy class of stampings;
K C - coefficient depending on the group of complexity of stampings;
K B - coefficient depending on the mass of forgings;
K M - coefficient depending on the brand of stamping material;
K P - coefficient depending on the annual program for the production of stampings;
Q is the mass of the workpiece, kg;
q is the mass of the finished part, kg;
S waste - the price of 1 ton of waste, rub.
C i = 315 rubles; Q = 1.25 kg; K T = 1; K C = 0.84; K B \u003d 1; K M = 1; K P \u003d 1;
q = 0.8 kg; S out \u003d 14.4 kg.
The economic effect for comparing the methods of obtaining blanks, in which the technological process of machining does not change, can be calculated by the formula:
,
where S E1, S E2 - the cost of the compared blanks, rub.;
N – annual program, pcs.
We define:
From the results obtained, it can be seen that the option of obtaining a workpiece by stamping is economically viable.
Production of blanks by stamping on various types equipment is a progressive method, as it significantly reduces the allowances for machining in comparison with obtaining a workpiece from rolled products, and is also characterized by a higher degree of accuracy and higher productivity. The stamping process also densifies the material and creates a directionality of the material fiber along the contour of the part.
Having solved the problem of choosing a method for obtaining a workpiece, you can proceed to the following steps term paper, which will gradually lead us to the direct compilation of the technological process for manufacturing the part, which is the main goal of the course work. The choice of the type of workpiece and the method of its production have the most direct and very significant influence on the nature of the construction of the technological process of manufacturing the part, since, depending on the chosen method for obtaining the workpiece, the amount of allowance for processing the part can fluctuate significantly and, therefore, it is not the set of methods that changes, used for surface treatment.
1.4 Purpose of methods and processing steps
The choice of processing method is influenced by the following factors that must be considered:
the shape and size of the part;
accuracy of processing and cleanliness of surfaces of parts;
economic feasibility of the chosen processing method.
Guided by the above points, we will begin to identify a set of processing methods for each surface of the part.
Figure 1.1 Sketch of the part with the designation of the layers removed during machining
All axle surfaces have rather high requirements for roughness. The turning of surfaces A, B, C, D, E, F, H, I, K is divided into two operations: rough (preliminary) and finishing (final) turning. When rough turning, we remove most of the allowance; processing is carried out with a large depth of cut and a large feed. The scheme that provides the shortest processing time is the most advantageous. When finishing turning, we remove a small part of the allowance, and the order of surface treatment is preserved.
When processing on lathe it is necessary to pay attention to the strong fastening of the part and the cutter.
To obtain the specified roughness and the required quality of the G and I surfaces, it is necessary to apply fine grinding, in which the accuracy of processing the outer cylindrical surfaces reaches the third class, and the surface roughness reaches 6-10 classes.
For greater clarity, we will schematically write down the selected processing methods for each surface of the part:
A: rough turning, finishing turning;
B: rough turning, finishing turning, threading;
B: rough turning, finishing turning;
G: rough turning, fine turning, fine grinding;
D: rough turning, finishing turning;
E: rough turning, finishing turning;
Zh: drilling, countersinking, deployment;
Z: rough turning, finishing turning;
And: rough turning, fine turning, fine grinding;
K: rough turning, finishing turning;
L: drilling, countersinking;
M: drilling, countersinking;
Now you can proceed to the next stage of the course work related to the choice of technical bases.
1.5 Selection of bases and sequence of processing
The workpiece of the part in the process of processing must take and maintain a certain position relative to the parts of the machine or fixture during the entire processing time. To do this, it is necessary to exclude the possibility of three rectilinear movements of the workpiece in the direction of the selected coordinate axes and three rotational movements around these or parallel axes (i.e., deprive the workpiece of the part of six degrees of freedom).
To determine the position of a rigid workpiece, six reference points are required. To place them, three coordinate surfaces are required (or three combinations of coordinate surfaces replacing them), depending on the shape and dimensions of the workpiece, these points can be located on the coordinate surface in various ways.
It is recommended to choose engineering bases as technological bases in order to avoid recalculation of operational dimensions. The axis is a cylindrical part, the design bases of which are the end surfaces. In most operations, the basing of the part is carried out according to the following schemes.
Figure 1.2 Scheme of setting the workpiece in a three-jaw chuck
In this case, when installing the workpiece in the chuck: 1, 2, 3, 4 - double guide base, which takes away four degrees of freedom - movement about the OX axis and the OZ axis and rotation around the OX and OZ axes; 5 - the support base deprives the workpiece of one degree of freedom - movement along the OY axis;
6 - support base, depriving the workpiece of one degree of freedom, namely, rotation around the OY axis;
Figure 1.3 Scheme of installing the workpiece in a vice
Taking into account the shape and dimensions of the part, as well as the accuracy of processing and surface cleanliness, sets of processing methods were selected for each surface of the shaft. We can determine the sequence of surface treatment.
Figure 1.4 Sketch of the part with the designation of surfaces
1. Turning operation. The workpiece is installed on the surface 4 in
self-centering 3-jaw chuck with end stop 5 for rough turning of end 9, surface 8, end 7, surface 6.
2. Turning operation. We turn the workpiece over and install it in a self-centering 3-jaw chuck along surface 8 with an emphasis on end 7 for rough turning of end 1, surface 2, end 3, surface 4, end 5.
3. Turning operation. The workpiece is installed on the surface 4 in
self-centering 3-jaw chuck with end stop 5 for fine turning of end face 9, face 8, face 7, face 6, chamfer 16 and groove 19.
4. Turning operation. We turn the workpiece over and install it in a self-centering 3-jaw chuck along surface 8 with an emphasis on end 7 for fine turning of end 1, surface 2, end 3, surface 4, end 5, chamfers 14, 15 and grooves 17, 18.
5. Turning operation. The workpiece is installed in a self-centering 3-jaw chuck along surface 8 with an emphasis on the end face 7 for drilling and countersinking surface 10, threading on surface 2.
6. Drilling operation. We set the part in a vice on surface 6 with an emphasis on the end face 9 for drilling, countersinking and reaming surface 11, drilling and countersinking surfaces 12 and 13.
7. Grinding operation. The part is installed on surface 4 in a self-centering 3-jaw chuck with a stop on the end face 5 for grinding surface 8.
8. Grinding operation. The part is installed on the surface 8 in a self-centering 3-jaw chuck with an emphasis on the end face 7 for grinding the surface 4.
9. Remove the part from the fixture and send it for inspection.
The workpiece surfaces are processed in the following sequence:
surface 9 - rough turning;
surface 8 - rough turning;
surface 7 - rough turning;
surface 6 - rough turning;
surface 1 - rough turning;
surface 2 - rough turning;
surface 3 - rough turning;
surface 4 - rough turning;
surface 5 - rough turning;
surface 9 - fine turning;
surface 8 - fine turning;
surface 7 - fine turning;
surface 6 - fine turning;
surface 16 - chamfer;
surface 19 - sharpen a groove;
surface 1 – fine turning;
surface 2 – fine turning;
surface 3 – fine turning;
surface 4 – fine turning;
surface 5 - fine turning;
surface 14 - chamfer;
surface 15 - chamfer;
surface 17 - sharpen a groove;
surface 18 - sharpen the groove;
surface 10 - drilling, countersinking;
surface 2 - threading;
surface 11 - drilling, reaming, reaming;
surface 12, 13 - drilling, countersinking;
surface 8 - fine grinding;
surface 4 - fine grinding;
As you can see, the surface treatment of the workpiece is carried out in order from coarser methods to more accurate ones. The last processing method in terms of accuracy and quality must meet the requirements of the drawing.
1.6 Development of route technological process
The part is an axis and belongs to the bodies of revolution. We process the workpiece obtained by stamping. When processing, we use the following operations.
010. Turning.
1. grind surface 8, cut end 9;
2. Turn surface 6, trim end 7
Cutter material: CT25.
Coolant brand: 5% emulsion.
015. Turning.
Processing is carried out on a turret lathe model 1P365.
1. grind surface 2, cut end 1;
2. grind surface 4, cut end 3;
3. cut end 5.
Cutter material: CT25.
Coolant brand: 5% emulsion.
The part is based in a three-jaw chuck.
As a measuring tool we use a bracket.
020. Turning.
Processing is carried out on a turret lathe model 1P365.
1. grind surfaces 8, 19, cut end 9;
2. grind surfaces 6, cut end 7;
3. chamfer 16.
Cutter material: CT25.
Coolant brand: 5% emulsion.
The part is based in a three-jaw chuck.
As a measuring tool we use a bracket.
025. Turning.
Processing is carried out on a turret lathe model 1P365.
1. grind surfaces 2, 17, cut end 1;
2. grind surfaces 4, 18, cut end 3;
3. cut end 5;
4. chamfer 15.
Cutter material: CT25.
Coolant brand: 5% emulsion.
The part is based in a three-jaw chuck.
As a measuring tool we use a bracket.
030. Turning.
Processing is carried out on a turret lathe model 1P365.
1. drill, countersink a hole - surface 10;
2. cut the thread - surface 2;
Drill material: ST25.
Coolant brand: 5% emulsion.
The part is based in a three-jaw chuck.
035. Drilling
Processing is carried out on a coordinate drilling machine 2550F2.
1. drill, countersink 4 stepped holes Ø9 - surface 12 and Ø14 - surface 13;
2. drill, countersink, ream hole Ø8 – surface 11;
Drill material: R6M5.
Coolant brand: 5% emulsion.
The part is based in a vise.
We use a caliber as a measuring tool.
040. Sanding
1. sanding the surface 8.
The part is based in a three-jaw chuck.
As a measuring tool we use a bracket.
045. Sanding
Processing is carried out on a circular grinding machine 3T160.
1. sanding the surface 4.
Select a grinding wheel for processing
PP 600×80×305 24A 25 N SM1 7 K5A 35 m/s. GOST 2424-83.
The part is based in a three-jaw chuck.
As a measuring tool we use a bracket.
050. Vibroabrasive
Processing is carried out in a vibroabrasive machine.
1. blunt sharp edges, remove burrs.
055. Flushing
Washing is done in the bathroom.
060. Control
They control all dimensions, check the roughness of the surfaces, the absence of nicks, the blunting of sharp edges. The control table is used.
1.7 Selection of equipment, tooling, cutting and measuring tools
axis workpiece cutting processing
The choice of machine equipment is one of the most important tasks in the development of the technological process of machining the workpiece. The productivity of part manufacturing, the economic use of production space, mechanization and automation depend on its correct choice. manual labor, electricity and, as a result, the cost of the product.
Depending on the volume of production of products, machines are selected according to the degree of specialization and high productivity, as well as machines with a numerical program management(CNC).
When developing a technological process for the machining of a workpiece, it is necessary to choose the right devices that should help increase labor productivity, processing accuracy, improve working conditions, eliminate preliminary marking of the workpiece and align them when installed on the machine.
The use of machine tools and auxiliary tools in the processing of workpieces provides a number of advantages:
improves the quality and accuracy of processing parts;
reduces the complexity of processing workpieces due to a sharp decrease in the time spent on installation, alignment and fixing;
expands technological capabilities machine tools;
creates the possibility of simultaneous processing of several workpieces fixed in a common fixture.
When developing a technological process for the machining of a workpiece, the choice of a cutting tool, its type, design and dimensions is largely determined by the processing methods, the properties of the material being machined, the required machining accuracy and the quality of the machined surface of the workpiece.
When choosing a cutting tool, you must strive to take standard tool, but, when appropriate, a special, combined, shaped tool should be used that allows you to combine the processing of several surfaces.
The correct choice of the cutting part of the tool is of great importance for increasing productivity and reducing the cost of machining.
When designing a technological process for machining a workpiece for interoperational and final control surfaces, a standard measuring tool should be used, taking into account the type of production, but at the same time, when appropriate, a special measuring tool or measuring fixture should be used.
The control method should help to increase the productivity of the inspector and the machine operator, create conditions for improving the quality of products and reducing their cost. In single and serial production, a universal measuring tool is usually used (caliper, depth gauge, micrometer, goniometer, indicator, etc.)
in mass and large-scale production it is recommended to use limit gauges (staples, plugs, templates, etc.) and active control methods, which are widely used in many branches of engineering.
1.8 Calculation of operating dimensions
Operational refers to the size affixed to the operational sketch and characterizing the size of the machined surface or the relative position of the machined surfaces, lines or points of the part. The calculation of operating dimensions is reduced to the task of correctly determining the value of the operating allowance and the value of the operating tolerance, taking into account the features of the developed technology.
Long operating dimensions are understood as dimensions that characterize the processing of surfaces with a one-sided allowance, as well as dimensions between axes and lines. The calculation of long operating dimensions is carried out in the following sequence:
1. Preparation of initial data (based on the working drawing and operational maps).
2. Drawing up a processing scheme based on the initial data.
3. Construction of a graph of dimensional chains to determine allowances, drawing and operational dimensions.
4. Drawing up a statement of calculation of operating sizes.
On the processing scheme (Figure 1.5), we place a sketch of the part indicating all the surfaces of a given geometric structure that occur during processing from the workpiece to the finished part. At the top of the sketch, all long drawing dimensions are indicated, drawing dimensions with tolerances (C), and at the bottom, all operating allowances (1z2, 2z3, ..., 13z14). Under the sketch in the processing table, dimension lines are indicated that characterize all dimensions of the workpiece, oriented with one-sided arrows, so that not a single arrow fits one of the surfaces of the workpiece, and only one arrow fits the rest of the surfaces. The following are dimension lines that characterize the dimensions of machining. Operating dimensions are oriented in the direction of the processed surfaces.
Figure 1.5 Scheme of part processing
On the graph of the initial structures connecting surfaces 1 and 2 with wavy edges characterizing the size of the allowance 1z2, surfaces 3 and 4 with additional edges characterizing the size of the allowance 3z4, etc. And we also draw thick edges of drawing sizes 2s13, 4s6, etc.
Figure 1.6 Graph of initial structures
top of the graph. Describes the surface of a part. The number in the circle indicates the number of the surface on the processing scheme.
Graph edge. Characterizes the type of connections between surfaces.
"z" - Corresponds to the value of the operating allowance, and "c" - to the drawing size.
Based on the developed processing scheme, a graph of arbitrary structures is built. The construction of the derived tree starts from the surface of the workpiece, to which no arrows are drawn in the processing scheme. In figure 1.5, such a surface is indicated by the number "1". From this surface we draw those edges of the graph that touch it. At the end of these edges, we indicate the arrows and the numbers of those surfaces to which the indicated dimensions are drawn. Similarly, we complete the graph according to the processing scheme.
Figure 1.7 Graph of derived structures
top of the graph. Describes the surface of a part.
Graph edge. The component link of the dimensional chain corresponds to the operational size or the size of the workpiece.
Graph edge. The closing link of the dimensional chain corresponds to the drawing size.
Graph edge. The closing link of the dimensional chain corresponds to the operating allowance.
On all edges of the graph we put down a sign (“+” or “-”), guided by the following rule: if the edge of the graph enters the vertex with a large number with its arrow, then we put the sign “+” on this edge, if the edge of the graph enters the vertex with its arrow with a lower number, then we put the “-” sign on this edge (Figure 1.8). We take into account that we do not know the operating dimensions, and according to the processing scheme (Figure 1.5), we determine approximately the value of the operating size or the size of the workpiece, using for this purpose the drawing dimensions and the minimum operating allowances, which are the sum of the microroughness values (Rz), the depth of the deformation layer (T) and spatial deviation (Δpr) obtained in the previous operation.
Column 1. In an arbitrary sequence, we rewrite all drawing dimensions and allowances.
Column 2. We indicate the numbers of operations in the sequence of their execution according to the route technology.
Column 3. Specify the name of the operations.
Column 4. We indicate the type of machine and its model.
Column 5. We place simplified sketches in one unchanged position for each operation, indicating the surfaces to be processed according to the route technology. Surfaces are numbered in accordance with the processing scheme (Figure 1.5).
Column 6. For each surface processed at this operation, we indicate the operating size.
Column 7. We do not perform heat treatment of the part at this operation, so we leave the column blank.
Column 8. It is filled in in exceptional cases, when the choice of the measuring base is limited by the conditions for the convenience of controlling the operational size. In our case, the graph remains free.
Column 9. Specify possible options surfaces that can be used as technological bases, taking into account the recommendations given in.
The choice of surfaces used as technological and measuring bases begins with the last operation in the reverse order of the technological process. We write down the equations of dimensional chains according to the graph of the initial structures.
After choosing the bases and operating dimensions, we proceed to the calculation of nominal values and the choice of tolerances for operating dimensions.
The calculation of long operating dimensions is based on the results of work on optimizing the structure of operating dimensions and is carried out in accordance with the sequence of work. The preparation of the initial data for calculating the operating sizes is carried out by filling in the columns
13-17 maps for choosing bases and calculating operational sizes.
Column 13. To close the links of dimensional chains, which are drawing dimensions, we write down the minimum values \u200b\u200bof these dimensions. To close the links, which are operational allowances, we indicate the value of the minimum allowance, which is determined by the formula:
z min \u003d Rz + T,
where Rz is the height of the irregularities obtained in the previous operation;
T is the depth of the defective layer formed during the previous operation.
The values of Rz and T are determined from the tables.
Column 14. For the closing links of dimensional chains, which are drawing dimensions, we write down the maximum values of these dimensions. The maximum values of the allowances are not yet put down.
Columns 15, 16. If the tolerance for the desired operating size will have a “-” sign, then in column 15 we put the number 1, if “+”, then in column 16 we put the number 2.
Column 17. We put down approximately the values \u200b\u200bof the determined operating dimensions, use the equations of dimensional chains from column 11.
1. 9A8 \u003d 8c9 \u003d 12 mm;
2. 9A5 = 3s9 - 3s5 = 88 - 15 = 73 mm;
3. 9A3 = 3s9 = 88 mm;
4. 7A9 \u003d 7z8 + 9A8 \u003d 0.2 + 12 \u003d 12mm;
5. 7A12 \u003d 3s12 + 7A9 - 9A3 \u003d 112 + 12 - 88 \u003d 36 mm;
6. 10A7 \u003d 7A9 + 9z10 \u003d 12 + 0.2 \u003d 12 mm;
7. 10A4 \u003d 10A7 - 7A9 + 9A5 + 4z5 \u003d 12 - 12 + 73 + 0.2 \u003d 73 mm;
8. 10A2 \u003d 10A7 - 7A9 + 9A3 + 2z3 \u003d 12 - 12 + 88 + 0.2 \u003d 88 mm;
9. 6A10 \u003d 10A7 + 6z7 \u003d 12 + 0.2 \u003d 12 mm;
10. 6A13 \u003d 6A10 - 10A7 + 7A12 + 12z13 \u003d 12 - 12 + 36 + 0.2 \u003d 36 mm;
11. 1A6 \u003d 10A2 - 6A10 + 1z2 \u003d 88 - 12 + 0.5 \u003d 77 mm;
12. 1A11 \u003d 10z11 + 1A6 + 6A10 \u003d 0.2 + 77 + 12 \u003d 89 mm;
13. 1A14 = 13z14 + 1A6 + 6A13 = 0.5 + 77 + 36 = 114 mm.
Column 18. We put down the values of tolerances for operational dimensions adopted according to the accuracy table 7, taking into account the recommendations set out in. After setting the tolerances in column 18, you can determine the maximum allowance values and put them in column 14.
The value of ∆z is determined from the equations in column 11 as the sum of the tolerances for the operating dimensions that make up the dimensional chain.
Column 19. In this column, the nominal values \u200b\u200bof the operating dimensions must be entered.
The essence of the method for calculating the nominal values of operating dimensions is reduced to solving the equations of dimensional chains recorded in column 11.
1. 8c9 = 9A89A8 =
2. 3s9 = 9A39A3 =
3. 3s5 = 3s9 - 9A5
9A5 \u003d 3s9 - 3s5 \u003d 
We accept: 9А5 = 73 -0.74
3s5 = 
4.9z10 = 10A7 - 7A9
10A7 = 7A9 + 9z10 = 
We accept: 10А7 = 13.5 -0.43 (correction + 0.17)
9z10= 
5. 4z5 \u003d 10A4 - 10A7 + 7A9 - 9A5
10A4 = 10A7 - 7A9 + 9A5 + 4z5 = 
We accept: 10А4 = 76.2 -0.74 (correction + 0.17)
4z5= 
6. 2z3 \u003d 10A2 - 10A7 + 7A9 - 9A3
10A2 = 10A7 - 7A9 + 9A3 + 2z3 = 
We accept: 10A2 = 91.2 -0.87 (correction + 0.04)
2z3 = 
7. 7z8 \u003d 7A9 - 9A8
7A9 = 7z8 + 9A8 = 
We accept: 7А9 = 12.7 -0.43 (correction: + 0.07)
7z8= 
8. 3s12 \u003d 7A12 - 7A9 + 9A3
7A12 \u003d 3s12 + 7A9 - 9A3 \u003d 
We accept: 7А12 = 36.7 -0.62
3s12= 
9.6z7 = 6A10 - 10A7
6A10 = 10A7 + 6z7 = 
We accept: 6А10 = 14.5 -0.43 (correction + 0.07)
6z7= 
10.12z13 = 6A13 - 6A10 + 10A7 - 7A12
6A13 = 6A10 - 10A7 + 7A12 + 12z13 = 
We accept: 6А13 = 39.9 -0.62 (correction + 0.09)
12z13= 
11. 1z2 \u003d 6A10 - 10A2 + 1A6
1A6 \u003d 10A2 - 6A10 + 1z2 \u003d 
We accept: 1А6 = 78.4 -0.74 (correction + 0.03)
1z2 = 
12.13z14 = 1A14 - 1A6 - 6A13
1A14=13z14+1A6+6A13= 
We accept: 1A14 = 119.7 -0.87 (correction + 0.03)
13z14= 
13. 10z11 = 1A11 - 1A6 - 6A10
1A11 = 10z11 + 1A6 + 6A10 = 
We accept: 1А11 = 94.3 -0.87 (correction + 0.03)
10z11= 
After calculating the nominal sizes, we enter them in column 19 of the base selection card and, with a tolerance for processing, write them down in the “note” column of the Processing Scheme (Figure 1.5).
After we fill in column 20 and the column "approx.", We apply the obtained values of operational dimensions with a tolerance to the sketches of the route technological process. This completes the calculation of the nominal values of the long operating dimensions.
| Map of base selection and calculation of operational sizes | ||||||||||||||||||
| master links | operation number | the name of the operation | Equipment model |
processing |
Operating |
Bases | Dimensional chain equations |
Closing links of dimensional chains | Operating dimensions | |||||||||
| Surfaces to be machined | Thermal Depth layer | Selected from the conditions of measurement convenience | Technological options. bases | Accepted technical nol. and measure. bases | Designation | Limit dimensions | Tolerance mark and approx. operating |
Value |
Rated meaning |
|||||||||
| min | max | |||||||||||||||||
|
magnitude |
||||||||||||||||||
| 5 | Prepare. | GCM |
|
13z14=1A14–1A–6A13 10z11=1A11–1A6-6A10 1z2=6А10–10А2+1А6 |
||||||||||||||
| 10 | Turning | 1P365 |  |
6 | 6 | 12z13=6A13–6A10+10A7–7A12 |
||||||||||||
Figure 1.9 Map of base selection and calculation of operating sizes
Calculation of operating dimensions with double-sided allowance
When processing surfaces with a two-sided allowance, it is advisable to calculate the operating dimensions using statistical method determining the value of the operating allowance, depending on the selected processing method and on the dimensions of the surfaces.
To determine the value of the operating allowance by a static method, depending on the processing method, we will use source tables.
To calculate the operating dimensions with a two-sided allowance, for such surfaces we draw up the following calculation scheme:
Figure 1.10 Layout of operating allowances
Drawing up a statement of calculation of diametrical operating dimensions.
Column 1: Indicates the numbers of operations according to the developed technology, in which the processing of this surface is performed.
Column 2: The processing method is indicated in accordance with the operating card.
Column 3 and 4: The designation and value of the nominal diametrical operating allowance, taken from the tables in accordance with the processing method and dimensions of the workpiece, are indicated.
Column 5: The designation of the operating size is indicated.
Column 6: According to the accepted processing scheme, equations are compiled for calculating the operating dimensions.
Filling out the statement begins with the final operation.
Column 7: The accepted operating size with a tolerance is indicated. The calculated value of the desired operating size is determined by solving the equation from column 6.
Sheet for calculating operating dimensions when machining the outer diameter of the axis Ø20k6 (Ø20)
Name operations |
Operating allowance | Operating size | ||||
| Designation | Value | Designation | Calculation formulas | Approximate size | ||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Zag | Stamping | Ø24 | ||||
| 10 | Turning (roughing) | D10 | D10=D20+2z20 | |||
| 20 | Turning (finishing) | Z20 | 0,4 | D20 | D20=D45+2z45 | |
| 45 | grinding | Z45 | 0,06 | D45 | D45=damn rr | |
Sheet for calculating operating dimensions when machining the outer diameter of the axis Ø75 -0.12
| 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Zag | Stamping | Ø79 | ||||
| 10 | Turning (roughing) | D10 | D10=D20+2z20 | Ø75.8 -0.2 | ||
| 20 | Turning (finishing) | Z20 | 0,4 | D20 | D20=damn rr |
Sheet for calculating operating dimensions when machining the outer diameter of the axis Ø30k6 (Ø30)
Sheet for calculating operating dimensions when processing the outer diameter of the shaft Ø20h7 (Ø20 -0.021)
| 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Zag | Stamping | Ø34 | ||||
| 15 | Turning (roughing) | D15 | D15=D25+2z25 | Ø20.8 -0.2 | ||
| 25 | Turning (finishing) | Z25 | 0,4 | D25 | D25=damn rr | Ø20 -0.021 |
Sheet for calculating operating dimensions when machining a hole Ø8Н7 (Ø8 +0.015)
Sheet for calculating operating dimensions when machining a hole Ø12 +0.07
Sheet for calculating operating dimensions when machining a hole Ø14 +0.07
Sheet for calculating operating dimensions when machining a hole Ø9 +0.058
After calculating the diametrical operational dimensions, we will apply their values to the sketches of the corresponding operations of the route description of the technological process.
1.9 Calculation of cutting conditions
When assigning cutting modes, the nature of processing, the type and dimensions of the tool, the material of its cutting part, the material and condition of the workpiece, the type and condition of the equipment are taken into account.
When calculating cutting conditions, set the depth of cut, minute feed, cutting speed. Let us give an example of calculating cutting conditions for two operations. For other operations, we assign cutting conditions according to, v.2, p. 265-303.
010 . Rough turning (Ø24)
Mill model 1P365, processed material - steel 45, tool material ST 25.
The cutter is equipped with a ST 25 carbide insert (Al 2 O 3 +TiCN+T15K6+TiN). The use of a carbide insert that does not need regrinding reduces the time spent on changing tools, in addition, the basis of this material is the improved T15K6, which significantly increases the wear resistance and temperature resistance of ST 25.
The geometry of the cutting part.
All parameters of the cutting part are selected from the source Cutter: α= 8°, γ = 10°, β = +3º, f = 45°, f 1 = 5°.
2. Brand coolant: 5% emulsion.
3. The depth of cut corresponds to the size of the allowance, since the allowance is removed in one trip.
4. Calculated feed is determined based on the requirements of roughness (, p. 266) and is specified according to the machine's passport.
S = 0.5 rpm.
5. Persistence, p.268.
6. Design cutting speed is determined from the specified tool life, feed and depth of cut from ,p.265.
where C v , x, m, y are coefficients [ 5 ], p.269;
T - tool life, min;
S - feed, rpm;
t – cutting depth, mm;
K v is a coefficient that takes into account the influence of the material of the workpiece.
K v = K m v ∙ K p v ∙ K and v ,
K m v - coefficient taking into account the influence of the properties of the material being processed on the cutting speed;
K p v = 0.8 - coefficient taking into account the influence of the state of the surface of the workpiece on the cutting speed;
K and v = 1 - coefficient taking into account the influence of the tool material on the cutting speed.
K m v = K g ∙,
where K g is a coefficient characterizing the steel group in terms of machinability.
K m v = 1∙
K v = 1.25 ∙ 0.8 ∙ 1 = 1,
7. Estimated speed.
where D is the workpiece diameter, mm;
V R - design cutting speed, m / min.
According to the passport of the machine, we accept n = 1500 rpm.
8. Actual cutting speed.
where D is the workpiece diameter, mm;
n is rotation frequency, rpm.
9. The tangential component of the cutting force Pz, H is determined by the source formula, p.271.
Р Z = 10∙С r ∙t x ∙S y ∙V n ∙К r,
where P Z is the cutting force, N;
C p, x, y, n - coefficients, p.273;
S - feed, mm / rev;
t – cutting depth, mm;
V – cutting speed, rpm;
К р – correction coefficient (К р = К mr ∙К j р ∙К g р ∙К l р, - numerical values of these coefficients from, pp. 264, 275).
K p \u003d 0.846 1 1.1 0.87 \u003d 0.8096.
P Z \u003d 10 ∙ 300 ∙ 2.8 ∙ 0.5 0.75 ∙ 113 -0.15 ∙ 0.8096 \u003d 1990 N.
10. Power from, p.271.
,
where Р Z – cutting force, N;
V – cutting speed, rpm.
.
The power of the electric motor of the 1P365 machine is 14 kW, so the drive power of the machine is sufficient:
N res.< N ст.
3.67 kW<14 кВт.
035. Drilling
Drilling hole Ø8 mm.
Machine model 2550F2, workpiece material - steel 45, tool material R6M5. Processing is carried out in one pass.
1. Substantiation of the brand of material and geometry of the cutting part.
Material of the cutting part of the tool R6M5.
Hardness 63…65 HRCe,
Bending strength s p \u003d 3.0 GPa,
Tensile strength s in \u003d 2.0 GPa,
Ultimate compressive strength s com = 3.8 GPa,
The geometry of the cutting part: w = 10° - the angle of inclination of the helical tooth;
f = 58° - the main angle in the plan,
a = 8° - rear angle to be sharpened.
2. Depth of cut
t = 0.5∙D = 0.5∙8 = 4 mm.
3. Estimated feed is determined based on the requirements of roughness .s 266 and is specified according to the machine's passport.
S = 0.15 rpm.
4. Persistence p. 270.
5. Design cutting speed is determined from the given tool life, feed and depth of cut.
where C v , x, m, y are the coefficients, p.278.
T - tool life, min.
S - feed, rpm.
t is the depth of cut, mm.
K V is a coefficient that takes into account the influence of the workpiece material, surface condition, tool material, etc.
6. Estimated speed.
where D is the workpiece diameter, mm.
V p - design cutting speed, m / min.
According to the passport of the machine, we accept n = 1000 rpm.
7. Actual cutting speed.
where D is the workpiece diameter, mm.
n - speed, rpm.
.
8. Torque
M cr \u003d 10 ∙ C M ∙ D q ∙ S y ∙ K r.
S - feed, mm / rev.
D – drilling diameter, mm.
M cr = 10∙0.0345∙ 8 2 ∙ 0.15 0.8 ∙0.92 = 4.45 N∙m.
9. Axial force R o, N on , s. 277;
R o \u003d 10 ∙ C R D q S y K R,
where C P, q, y, K p, are the coefficients p.281.
P o \u003d 10 ∙ 68 8 1 0.15 0.7 0.92 \u003d 1326 N.
9. Cutting power.
where M cr - torque, N∙m.
V – cutting speed, rpm.
0.46 kW< 7 кВт. Мощность станка достаточна для заданных условий обработки.
040. Sanding
Machine model 3T160, workpiece material - steel 45, tool material - normal electrocorundum 14A.
Plunge grinding by the periphery of the circle.
1. Brand of material, geometry of the cutting part.
Choose a circle:
PP 600×80×305 24A 25 N SM1 7 K5A 35 m/s. GOST 2424-83.
2. Depth of cut
3. Radial feed S p, mm / rev is determined by the formula from the source, s. 301, tab. 55.
S P \u003d 0.005 mm / rev.
4. The speed of the circle V K, m / s is determined by the formula from the source, p. 79:
where D K is the diameter of the circle, mm;
D K = 300 mm;
n K \u003d 1250 rpm - the rotational speed of the grinding spindle.
5. The estimated rotational speed of the workpiece n z.r, rpm is determined by the formula from the source, p.79.
where V Z.R is the selected workpiece speed, m/min;
V З.Р we will define according to tab. 55, p. 301. Let's take V Z.R = 40 m/min;
d З – workpiece diameter, mm;
6. Effective power N, kW will be determined according to the recommendation in
source page 300:
for plunge grinding with the periphery of the wheel
where the coefficient C N and the exponents r, y, q, z are given in, table. 56, p. 302;
V Z.R – billet speed, m/min;
S P - radial feed, mm / rev;
d З – workpiece diameter, mm;
b – grinding width, mm, is equal to the length of the workpiece section to be ground;
The power of the electric motor of the 3T160 machine is 17 kW, so the drive power of the machine is sufficient:
N cut< N шп
1.55 kW< 17 кВт.
1.10 Rationing operations
Settlement and technological norms of time are determined by calculation.
There are the norm of piece time T pcs and the norm of time calculation. The calculation norm is determined by the formula on page 46, :
where T pcs - the norm of piece time, min;
T p.z. - preparatory-final time, min;
n is the number of parts in the batch, pcs.
T pcs \u003d t main + t auxiliary + t service + t lane,
where t main is the main technological time, min;
t aux - auxiliary time, min;
t service - time of service of the workplace, min;
t lane - time of breaks and rest, min.
The main technological time for turning, drilling operations is determined by the formula on page 47, :
where L is the estimated processing length, mm;
Number of passes;
S min - minute feed of the tool;
a - the number of simultaneously processed parts.
The estimated processing length is determined by the formula:
L \u003d L res + l 1 + l 2 + l 3.
where L cut - cutting length, mm;
l 1 - tool supply length, mm;
l 2 - tool insertion length, mm;
l 3 - tool overrun length, mm.
The service time of the workplace is determined by the formula:
t service = t maintenance + t org.service,
where t maintenance - maintenance time, min;
t org.service - organizational service time, min.
,
,
where is the coefficient determined by the standards. We accept.
Time for a break and rest is determined by the formula:
,
where is the coefficient determined by the standards. We accept.
We present the calculation of the norms of time for three different operations
010 Turning
Let us first determine the estimated processing length. l 1 , l 2 , l 3 will be determined according to the data of tables 3.31 and 3.32 on page 85 .
L = 12 + 6 +2 = 20 mm.
Minute feed
S min \u003d S about ∙n, mm / min,
where S about - reverse feed, mm / about;
n is the number of revolutions, rpm.
S min = 0.5∙1500 = 750 mm/min.
min.
Auxiliary time consists of three components: for installation and removal of the part, for the transition, for measurement. This time is determined by cards 51, 60, 64 on pages 132, 150, 160 according to:
t set / removed = 1.2 min;
t transition = 0.03 min;
t meas = 0.12 min;
tsp \u003d 1.2 + 0.03 + 0.12 \u003d 1.35 min.
Maintenance time
min.
Organizational service time
min.
Break times
min.
The norm of piece time for the operation:
T pcs \u003d 0.03 + 1.35 + 0.09 + 0.07 \u003d 1.48 min.
035 Drilling
Drilling hole Ø8 mm.
Let's determine the estimated processing length.
L = 12 + 10.5 + 5.5 = 28 mm.
Minute feed
S min = 0.15∙800 = 120 mm/min.
Main technological time:
min.
Processing is done on a CNC machine. The cycle time of automatic operation of the machine according to the program is determined by the formula:
T c.a \u003d T o + T mv, min,
where T o - the main time of automatic operation of the machine, T o \u003d t main;
Tmv - machine-auxiliary time.
T mv \u003d T mv.i + T mv.x, min,
where T mv.i - machine-auxiliary time for automatic tool change, min;
T mv.h - machine auxiliary time for the execution of automatic auxiliary moves, min.
T mv.i is determined according to Appendix 47,.
We accept T mv.x \u003d T about / 20 \u003d 0.0115 min.
T c.a \u003d 0.23 + 0.05 + 0.0115 \u003d 0.2915 min.
The norm of piece time is determined by the formula:
where T in - auxiliary time, min. Determined by map 7, ;
a teh, a org, a ex – time for service and rest, determined by , map 16: a te + a org + a ex = 8%;
T in = 0.49 min.
040. Sanding
Definition of the main (technological) time:
where l is the length of the processed part;
l 1 - the value of the infeed and overrun of the tool on the map 43, ;
i is the number of passes;
S - tool feed, mm.
min
For the definition of auxiliary time, see card 44,
T in \u003d 0.14 + 0.1 + 0.06 + 0.03 \u003d 0.33 min
Determination of time for maintenance of the workplace, rest and natural needs:
,
where а obs and а otd - time for maintenance of the workplace, rest and natural needs as a percentage of the operational time on the map 50, :
a obs = 2% and a det = 4%.
Definition of the norm of piece time:
T w \u003d T o + T in + T obs + T otd \u003d 3.52 + 0.33 + 0.231 \u003d 4.081 min
1.11 Economic comparison of 2 options for operations
When developing a technological process of mechanical processing, the task arises to choose from several processing options one that provides the most economical solution. Modern methods of machining and a wide variety of machine tools allow you to create various technology options that ensure the manufacture of products that fully meet all the requirements of the drawing.
In accordance with the provisions for evaluating the economic efficiency of new technology, the most profitable option is recognized for which the sum of current and reduced capital costs per unit of output will be minimal. The sum of the reduced costs should include only those costs that change their value when switching to a new version of the technological process.
The sum of these costs, related to the hours of operation of the machine, can be called hourly present costs.
Consider the following two options for performing a turning operation, in which processing is carried out on different machines:
1. according to the first option, rough turning of the outer surfaces of the part is carried out on a universal screw-cutting lathe model 1K62;
2. According to the second option, rough turning of the outer surfaces of the part is carried out on a turret lathe model 1P365.
1. Operation 10 is performed on the machine 1K62.
The value characterizes the efficiency of the equipment. A lower value for comparing machines with equal productivity indicates that the machine is more economical.
Hourly present cost
where - the main and additional wages, as well as accruals on social insurance to the operator and adjuster for the physical hour of operation of the serviced machines, kop/h;
The multi-station coefficient, taken according to the actual state in the area under consideration, is taken as M = 1;
Hourly costs for the operation of the workplace, kop/h;
Normative coefficient of economic efficiency of capital investments: for mechanical engineering = 2;
Specific hourly capital investments in the machine, kop/h;
Specific hourly capital investments in the building, kop / h.
The basic and additional wages, as well as social security contributions to the operator and the adjuster can be determined by the formula:
, kop / h,
where is the hourly tariff rate of a machine operator of the corresponding category, kop/h;
1.53 is the total coefficient representing the product of the following partial coefficients:
1.3 - coefficient of compliance with the norms;
1.09 - coefficient of additional salary;
1.077 - the coefficient of contributions to social security;
k - coefficient taking into account the salary of the adjuster, we take k \u003d 1.15.
The amount of hourly costs for the operation of the workplace in case of reduction
The machine load must be corrected with a factor if the machine cannot be reloaded. In this case, the adjusted hourly cost is:
, kop / h,
where - hourly costs for the operation of the workplace, kop/h;
Correction factor:
,
The share of semi-fixed costs in hourly costs at the workplace, we accept;
Machine load factor.
where Т ШТ – unit time for the operation, Т ШТ = 2.54 min;
t B is the release cycle, we accept t B = 17.7 min;
m P - the accepted number of machines for operations, m P = 1.
;
,
where - practical adjusted hourly costs at the base workplace, kop;
Machine coefficient showing how many times the costs associated with the operation of this machine are greater than those of the base machine. We accept.
kop/h
The capital investment in the machine and the building can be determined by:
where C is the book value of the machine, we take C = 2200.
, kop / h,
Where F is the production area occupied by the machine, taking into account the passes:
where - the production area occupied by the machine, m 2;
The coefficient taking into account the additional production area, .
kop/h
kop/h
The cost of machining for the operation in question:
, cop.
cop.
2. Operation 10 is performed on the machine 1P365.
C \u003d 3800 rubles.
T PCS = 1.48 min.
kop/h
kop/h
kop/h
cop.
Comparing the options for performing a turning operation on various machines, we come to the conclusion that the turning of the outer surfaces of the part should be carried out on a 1P365 turret lathe. Since the cost of machining a part is lower than if it is performed on a machine model 1K62.
2. Design of special machine tools
2.1 Initial data for the design of machine tools
In this course project, a machine fixture has been developed for operation No. 35, in which drilling, countersinking and reaming holes are performed using a CNC machine.
The type of production, the release program, as well as the time spent on the operation, which determine the level of speed of the device when installing and removing the part, influenced the decision to mechanize the device (the part is clamped in ticks by a pneumatic cylinder).
The fixture is used to install only one part.
Consider the scheme of basing the part in the fixture:
Figure 2.1 Scheme of installing the part in a vice
1, 2, 3 - mounting base - deprives the workpiece of three degrees of freedom: movement along the OX axis and rotation around the OZ and OY axes; 4, 5 - double support base - deprives two degrees of freedom: movement along the axes OY and OZ; 6 - support base - deprives of rotation around the OX axis.
2.2 Schematic diagram of the machine tool
As a machine tool, we will use a machine vice equipped with a pneumatic drive. Pneumatic actuator provides constant workpiece clamping force, as well as fast clamping and detachment of the workpiece.
2.3 Description of construction and principle of operation
Universal self-centering vice with two movable replaceable jaws is designed to secure axle-type parts during drilling, countersinking and reaming holes. Consider the design and principle of operation of the device.
On the left end of the body 1 of the vise, an adapter sleeve 2 is fixed, and on it is a pneumatic chamber 3. Between the two covers of the pneumatic chamber, a diaphragm 4 is clamped, which is rigidly fixed on a steel disk 5, in turn, fixed on the rod 6. The rod 6 of the pneumatic chamber 3 is connected through a rod 7 with a rolling pin 8, at the right end of which there is a rail 9. The rail 9 is engaged with the gear wheel 10, and the gear wheel 10 is engaged with the upper movable rail 11, on which the right movable sponge is installed and secured with two pins 23 and two bolts 17 12. The lower end of the pin 14 enters the annular groove at the left end of the rolling pin 8, its upper end is pressed into the hole of the left movable jaw 13. Replaceable clamping prisms 15, corresponding to the diameter of the axis being machined, are fixed with screws 19 on the movable jaws 12 and 13. The pneumatic chamber 3 is attached to the adapter sleeve 2 using 4 bolts 18. In turn, the adapter sleeve 2 is attached to the fixture body 1 using bolts 16.
When compressed air enters the left cavity of the pneumatic chamber 3, the diaphragm 4 bends and moves the rod 6, the rod 7 and the rolling pin 8 to the right. to the left. Thus, the jaws 12 and 13, moving, clamp the workpiece. When compressed air enters the right cavity of the pneumatic chamber 3, the diaphragm 4 bends in the other direction and the rod 6, the rod 7 and the rolling pin 8 are moved to the left; rolling pin 8 spreads sponges 12 and 13 with prisms 15.
2.4 Calculation of the machine fixture
Force calculation fixture
Figure 2.2 Scheme for determining the clamping force of the workpiece
To determine the clamping force, we simply depict the workpiece in the fixture and depict the moments from the cutting forces and the desired required clamping force.
In figure 2.2:
M - torque on the drill;
W is the required fixing force;
α is the angle of the prism.
The required clamping force of the workpiece is determined by the formula:
, H,
where M is the torque on the drill;
α is the angle of the prism, α = 90;
The coefficient of friction on the working surfaces of the prism, we accept ;
D is the workpiece diameter, D = 75 mm;
K is the safety factor.
K = k 0 ∙k 1 ∙k 2 ∙k 3 ∙k 4 ∙k 5 ∙k 6 ,
where k 0 is the guaranteed safety factor, for all processing cases k 0 = 1.5
k 1 - coefficient taking into account the presence of random irregularities on the workpieces, which entails an increase in cutting forces, we accept k 1 = 1;
k 2 - coefficient taking into account the increase in cutting forces from progressive blunting of the cutting tool, k 2 = 1.2;
k 3 - coefficient taking into account the increase in cutting forces during interrupted cutting, k 3 \u003d 1.1;
k 4 - coefficient taking into account the variability of the clamping force when using pneumatic lever systems, k 4 \u003d 1;
k 5 - coefficient taking into account the ergonomics of manual clamping elements, we take k 5 = 1;
k 6 - coefficient taking into account the presence of moments tending to rotate the workpiece, we take k 6 =1.
K = 1.5∙1∙1.2∙1.1∙1∙1∙1 = 1.98.
Torque
M \u003d 10 ∙ C M ∙ D q ∙ S y ∙ K r.
where C M, q, y, K p, are the coefficients, p.281.
S - feed, mm / rev.
D – drilling diameter, mm.
М = 10∙0.0345∙ 8 2 ∙ 0.15 0.8 ∙0.92 = 4.45 N∙m.
N.
Let us determine the force Q on the rod of the diaphragm pneumatic chamber. The force on the rod changes as it moves, since the diaphragm begins to resist in a certain area of \u200b\u200bdisplacement. The rational length of the rod stroke, at which there is no sharp change in the force Q, depends on the calculated diameter D, thickness t, material and design of the diaphragm, and also on the diameter d of the supporting disk.
In our case, we take the diameter of the working part of the diaphragm D = 125 mm, the diameter of the support disk d = 0.7∙D = 87.5 mm, the diaphragm is made of rubberized fabric, the thickness of the diaphragm is t = 3 mm.
Force in the initial position of the rod:
, H,
Where p is the pressure in the pneumatic chamber, we take p = 0.4∙10 6 Pa.
The force on the rod when moving 0.3D:
, N.
Calculation of fixture for accuracy
Based on the accuracy of the maintained size of the workpiece, the following requirements are imposed on the corresponding dimensions of the fixture.
When calculating the accuracy of fixtures, the total error in the processing of the part should not exceed the tolerance value T of the size, i.e.
The total fixture error is calculated using the following formula:
where T is the tolerance of the size being performed;
Based error, since in this case there is no deviation of the actually achieved position of the part from the required one;
Pinning error, ;
Fixture installation error on the machine, ;
Part position error due to wear of fixture elements;
Approximate wear of the installation elements can be determined by the formula:
,
where U 0 is the average wear of the mounting elements, U 0 = 115 µm;
k 1 , k 2 , k 3 , k 4 are coefficients, respectively, taking into account the influence of the workpiece material, equipment, processing conditions and the number of workpiece settings.
k 1 = 0.97; k 2 = 1.25; k 3 = 0.94; k4 = 1;
We accept microns;
Error from skew or displacement of the tool, since there are no guide elements in the fixture;
The coefficient taking into account the deviation of the dispersion of the values of the constituent quantities from the law of normal distribution,
Coefficient that takes into account the reduction in the limiting value of the basing error when working on tuned machines,
A coefficient that takes into account the share of the processing error in the total error caused by factors independent of the fixture,
Economic accuracy of processing, = 90 microns.
3. Design of special control equipment
3.1 Initial data for the design of the test fixture
Control and measuring devices are used to check the compliance of the parameters of the manufactured part with the requirements of technological documentation. Preference is given to devices that allow you to determine the spatial deviation of some surfaces in relation to others. This device meets these requirements, because. measures radial runout. The device has a simple device, is convenient in operation and does not require high qualification of the controller.
Parts of the axle type in most cases transmit significant torques to the mechanisms. In order for them to work flawlessly for a long time, the high accuracy of the execution of the main working surfaces of the axis in terms of diametrical dimensions is of great importance.
The inspection process mainly involves a complete check of the radial runout of the outer surfaces of the axle, which can be carried out on a multidimensional inspection fixture.
3.2 Schematic diagram of the machine tool
Figure 3.1 Schematic diagram of the test fixture
Figure 3.1 shows a schematic diagram of a device for controlling the radial runout of the outer surfaces of the axle part. The diagram shows the main parts of the device:
1 - fixture body;
2 - headstock;
3 - tailstock;
4 - rack;
5 - indicator heads;
6 - controlled detail.
3.3 Description of construction and principle of operation
The headstock 2 with a mandrel 20 and the tailstock 3 with a fixed reverse center 23 are fixed on the body 1 with the help of screws 13 and washers 26, on which the axle to be checked is mounted. The axial position of the axis is fixed by a fixed reverse center 23. The axis is pressed against the latter by a spring 21, which is located in the central axial hole of the quill 5 and acts on the adapter 6. The quill 5 is mounted in the headstock 2 with the possibility of rotation relative to the longitudinal axis thanks to the bushings 4. at the left end quill 5, a handwheel 19 with a handle 22 is installed, which is fixed with a washer 8 and a pin 28, the torque from the handwheel 19 is transmitted to the quill 5 using the key 27. The rotational movement during measurement is transmitted to the adapter 6 through the pin 29, which is pressed into the quill 5. In addition , at the other end of the adapter 6, a mandrel 20 with a conical working surface is inserted for accurate backlash-free locating of the axis, since the latter has a cylindrical axial hole with a diameter of 12 mm. The taper of the mandrel depends on the tolerance T and the diameter of the axle hole and is determined by the formula:
mm.
In two racks 7, attached to the body 1 with screws 16 and washers 25, a shaft 9 is installed, along which brackets 12 move and are fixed with screws 14. On brackets 12, rolling pins 10 are installed with screws 14, on which screws 15, nuts 17 and washers 24 fixed IG 30.
Two IG 30 serve to check the radial runout of the outer surfaces of the axis, which give one or two turns and count the maximum readings of the IG 30, which determine the runout. The device provides high performance of the control process.
3.4 Calculation of the test fixture
The most important condition that control devices must satisfy is to ensure the necessary measurement accuracy. Accuracy largely depends on the method of measurement adopted, on the degree of perfection of the concept and design of the device, as well as on the accuracy of its manufacture. An equally important factor affecting the accuracy is the accuracy of the surface used as a measuring base for the controlled parts.
where is the error in the manufacture of the installation elements and their location on the body of the device, we take mm;
The error caused by the inaccuracy in the manufacture of transmission elements is taken mm;
The systematic error, taking into account the deviations of the mounting dimensions from the nominal ones, is taken mm;
Basing error, accept ;
The error of the displacement of the measuring base of the part from the given position, we accept mm;
Fixing error, accept mm;
The error from the gaps between the axes of the levers, we accept;
The error of deviation of the installation elements from the correct geometric shape, we accept;
Measurement method error, accept mm.
The total error can be up to 30% of the controlled parameter tolerance: 0.3∙T = 0.3∙0.1 = 0.03 mm.
0.03 mm ≥ 0.0034 mm.
3.5 Development of a setup chart for operation No. 30
The development of a setup map allows you to understand the essence of setting up a CNC machine when performing an operation with an automatic method for obtaining a given accuracy.
As the tuning dimensions, we accept the dimensions corresponding to the middle of the tolerance field of the operational size. The tolerance value for the setting size is accepted
T n \u003d 0.2 * T op.
where T n is the tolerance for the setting size.
T op - tolerance for the operating size.
For example, in this operation we sharpen the surface Ø 32.5 -0.08, then the setting size will be equal to
32.5 - 32.42 = 32.46 mm.
T n \u003d 0.2 * (-0.08) \u003d - 0.016 mm.
Setting size Ø 32.46 -0.016 .
The calculation of other dimensions is carried out similarly.
Project Conclusions
According to the assignment for the course project, a technological process for manufacturing the shaft was designed. The technological process contains 65 operations, for each of which cutting conditions, time standards, equipment and tooling are indicated. For the drilling operation, a special machine tool has been designed to ensure the required accuracy of the workpiece, as well as the required clamping force.
When designing the technological process of manufacturing the shaft, a setup chart for turning operation No. 30 was developed, which allows you to understand the essence of setting up a CNC machine when performing an operation with an automatic method for obtaining a given accuracy.
During the implementation of the project, a settlement and explanatory note was drawn up, which describes in detail all the necessary calculations. Also, the settlement and explanatory note contains applications, which include operational maps, as well as drawings.
Bibliography
1. Handbook of technologist-machine builder. In 2 volumes / ed. A.G. Kosilova and R.K. Meshcheryakova.-4th ed., revised. and additional - M .: Mashinostroenie, 1986 - 496 p.
2. Granovsky G.I., Granovsky V.G. Metal cutting: Textbook for mechanical engineering. and instrumentation specialist. universities. _ M.: Higher. school, 1985 - 304 p.
3. Marasinov M.A. Guidelines for calculating operating sizes. - Rybinsk. RGATA, 1971.
4. Marasinov M.A. Design of technological processes in mechanical engineering: Textbook. - Yaroslavl. 1975.-196 p.
5. Mechanical Engineering Technology: Textbook for the implementation of the course project / V.F. Bezyazychny, V.D. Korneev, Yu.P. Chistyakov, M.N. Averyanov.- Rybinsk: RGATA, 2001.- 72 p.
6. General machine-building standards for auxiliary, for servicing the workplace and preparatory - final for the technical regulation of machine work. Mass production. M, Mechanical engineering. 1964.
7. Anserov M.A. Devices for metal-cutting machine tools. 4th edition, corrected. and additional L., Mechanical engineering, 1975
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1. Descriptiondesign and purpose of the part
Axes serve to support various parts of machines and mechanisms rotating with them or on them. The rotation of the axis, together with the parts installed on it, is carried out relative to its supports, called bearings. An example of a non-rotating axle is the axle of a hoisting machine block, and a rotating axle is a wagon axle. The axles perceive the load from the parts located on them and work in bending.
The design of the axle, its dimensions and rigidity, technical requirements, production program are the main factors that determine the manufacturing technology and the equipment used.
All axle journals are surfaces of rotation of relatively high precision. This determines the expediency of using turning operations only for their preliminary processing, and the final processing in order to ensure the specified dimensional accuracy and surface roughness should be performed by grinding. To ensure high requirements for the accuracy of the location of the axle journals, their final processing must be carried out in one installation or, in extreme cases, on the same bases.
The part is a body of revolution and consists of simple structural elements, presented in the form of bodies of revolution of a circular cross section of various diameters and lengths. The axis length is 370 mm, the maximum diameter is 50 mm, the minimum is 48, the maximum hole diameter is 14H12 (+0.18), and the minimum is 10 mm.
According to fig. it can be seen that the axis part has the following surfaces:
Surface 1 and 2 fig. 1: a square with a side of 40d11 mm and top deviations -0.08, bottom -0.24, roughness Ra = 6.3 µm.
Surface 3 and 5 fig. 1: diameter 50d11 mm and top deviations -0.08, bottom -0.24; roughness Ra = 6.3 µm
Surface 4 fig. 1: diameter 48mm; roughness Ra = 6.3 µm.
Surface 6 fig. 1: hole diameter 14H12; upper deviation +0.18, K3/8 thread; roughness Ra = 3.2 µm
Almost all surfaces of the axis are considered basic because they are mated with the corresponding surfaces of other machine parts or are directly involved in the working process of the machine. This explains the rather high requirements for the accuracy of the part processing and the degree of roughness indicated in the drawing.
It can be noted that the design of the part fully meets its official purpose. But the principle of manufacturability of the design is not only to meet the operational requirements, but also the requirements of the most rational and economical manufacture of the product.
The part has surfaces that are easily accessible for processing; sufficient rigidity of the part allows it to be processed on machines with the most productive cutting conditions. This part is technologically advanced, as it contains simple surface profiles, its processing does not require specially designed fixtures and machines. Axis surfaces are processed on turning, drilling, milling and grinding machines. The required dimensional accuracy and surface roughness are achieved by a relatively small set of simple operations, as well as a set of standard cutters, milling cutters and grinding wheels.
2. Workpiece material
The chemical composition of steel 40X GOST4543 is presented in table 1.
Table 1
The workpiece of the “axis” part is made of structural alloyed steel of the Stal40Kh GOST4543 grade.
Table 1 shows that in the chemical composition of steel 40X GOST4543, the maximum percentage of Chromium (Cr) is 0.80 - 1.10, and the minimum percentage of Phosphorus (P) is 0.035 and Sulfur (S) is 0.035.
The mechanical properties of steel 40X GOST4543 are presented in Table 2.
table 2
The physical properties of steel 40X GOST4543 are presented in Appendix 1.
Technological route for processing the part "axis"
|
Name equipment |
Cutting conditions |
Time\min |
||||
|
Procurement Select a workpiece circle w 60 mm Steel 40X GOST4543 Cut the workpiece to a size of 380 mm |
Band saw machine |
|||||
|
Turning cut end Sharpen (rough) outer w 52 mm and outer w 49 mm to a distance of 140 mm drill holes w 14H to a depth of 205 mm cut thread K 3/8? |
Lathe 16K20 cutting cutter t5k10 Cutter T15K6 Drill w 14 mm Tap K 3/8"" for R6M5 conical thread |
|||||
|
Drill holes sh 10 |
drilling vertical machine 2H135 drill w 10 mm |
|||||
|
Milling Mill a square from 2 sides to a size of 60 mm with a side of 40d11 ((-0.08) / (-0.24)) |
||||||
|
Thermo. treatment |
||||||
|
Turning (finishing) Sharpen up to w 50d11 in size 55 mm and up to w 48 mm in size 140 mm |
Lathe 16K20 |
|||||
|
Locksmith Blunt sharp edges |
file |
|||||
|
Control |
Check for compliance with the specified parameters |
Operation 005 cut the workpiece to a size of 380 mm. Band saw equipment is equipment for cutting metal profiles of different sections and diameters by sawing into workpieces of different lengths. The list of materials to be sawn using band saws is steel and its alloys. Method of basing clamp in tesky.
Operation 010 Turning cut the end, sharpen (rough) outer w 52 mm and outer w 48 mm to a distance of 140 mm drill hole w 14H12 (+0.18) to a depth of 205 mm cut a thread K 3/8?. Equipment: the 16K20 lathe is a universal screw-cutting lathe, which can be used to turn materials in the form of bodies of revolution, cutting modular, metric, and also to carry out a wide range of turning procedures (drilling using different types of drills, countersinking, and so on) with hot-rolled and cold-rolled products. Basing when turning in centers, when drilling holes sh 14H12 (+0.18) and threading K 3/8? clamp into a three-jaw chuck.
Cutting cutter T5K10, 32x20x170 mm, GOST 18884-73
Plate hard alloy Т5К10
Through-hole cutter T15K6 20x30x170 2102-0059
Line turning cutter (right and left) with a T15K6 carbide insert, GOST 18878, used for turning external surfaces and chamfers.
K3/8 machine-manual tap for taper inch thread GOST 6227 scope - cutting of internal taper inch thread with a profile angle of 60° by machine or by hand.
Operation 015 drilling, drilling holes. sh 10. Equipment vertical drilling machine 2H135, with the help of which the operations of drilling, reaming and reaming holes, as well as trimming and reaming can be equally successfully performed. 2H135 machines are also easy to use due to the fact that with the help of the feed box and spindle speeds, you can select the optimal modes for obtaining and processing holes with different parameters and in materials with different characteristics.
A drill is a cutting tool, with a rotary cutting motion and an axial feed motion, designed to make holes in a continuous layer of material.
Operation 020 Milling, mill a square from 2 sides to a size of 60 mm with a side of 40d11 ((-0.08)/(-0.24)). Equipment horizontal milling machine X6132 is a multifunctional machine designed for various processing of metal parts. It is able to process flat, stepped surfaces, cut grooves and cut gears with cylindrical, angle, end, shaped, spherical cutters. The reinforced design of the machine allows you to load heavy workpieces weighing up to 500 kg. Good performance is due to high power and a wide range of processing speeds. The use of modern cutting tools allows you to achieve better results.
End mill, material - high-speed steel P18, number of teeth - 18. The productivity of the end mill is low, and the described method of milling square faces can be recommended for small-scale production.
Operation 025 heat treatment Rockwell hardness 34…42 HRC
Operation 030 turning (finishing) to sharpen up to w 50d11 in size 55 mm
Equipment lathe 16K20. Bases in the centers.
Operation 035 locksmith to blunt the edges. File equipment.
Operation 040 control check for compliance with the specified parameters.
The ShTsT-1 equipment is universal, the jaws of which are located in one direction and are made of carbide materials; a threaded plug gauge is used to check the internal thread.
3. Determining the type of production
The nature of the technological process largely depends on the type of production of parts (single, serial, mass). This is due to the fact that in various types of industries it is economically expedient to use equipment, devices, different in complexity and versatility of cutting and measuring tools that differ in degree of versatility, mechanization and automation. Depending on the type of production, the organizational structures of the workshop also change significantly: the arrangement of equipment, systems for servicing workplaces, and the range of parts. According to Table 4, we preliminarily set the type of production depending on the weight and number of parts to be manufactured during the year.
Table 4. Type of production
|
Part weight, kg. |
Type of production |
|||||
|
single |
Small-scale |
Medium series |
large-scale |
Mass |
||
Serial production is conditionally divided into small-scale, medium-scale and large-scale production, depending on the number of parts in the series. Thus, with an annual output of 350 pieces/year, our production is small-scale.
Workpiece basing
010 Turning operation (roughing)
Equipment
Screw-cutting lathe model 16K20: Table 5
Table 5
fixture
Rotating centers according to GOST 8742-92.
Cutting tool
Cut-off turning cutter T5K10, 32x20x170 mm, GOST 18884-73 T5K10 hard alloy plate, straight through cutter T15K6 20x30x170 2102-0059, straight through straight turning cutter (right and left) with T15K6 hard alloy plate, GOST 18878.
Measuring tool
Caliper ShTs-I according to GOST 166-80, measurement limit 0-125 mm, division value 1 mm, measurement accuracy 0.1 mm.
4. Cutting conditions
a) First pass. Sharpen the part on top rough to Ш52 at length l=370 mm; Ra=12.5 µm.
1) Depth of cut for end face t = 5 mm.
2) Feed according to the reference book sp \u003d 0.45 mm / rev.
3) Cutting speed v, m/min.
where Сv=350 - Considers the material being processed and the material of the cutting part of the cutter;
m = 0.2 xV=0.15 yV = 0.35 - exponents;
T = 60 - tool life, min;
Kv - speed coefficient
where KPV \u003d 0.96 - the state of delivery of the workpiece;
КIV =0.65 - material of the cutting part;
KMV = 0.90 - processed material;
K=0.70 - coefficient of the cutter parameter;
Kg=0.97 - coefficient of the cutter parameter.
0.96 0.65 0.90 0.70 0.97=0.38
All values of the coefficients are selected according to the recommendation of the handbook.
4) The number of revolutions of the spindle.
5) Spindle speed according to the passport n=1000 rpm.
7) Cutting force.
Рz=Срz tхр syp vpr kr,
where kр - coefficient of power
where k1=1.04 - processed material.
k2=0.89 - main angle in plan
kp=1.04 0.89=0.93
Ср=3200 - processed material and material of the cutting part
Рz=3000 4.51.0 0.650.75 56.54-0.15 0.93=5424 N
8) Effective cutting power.
where h \u003d 0.75 - efficiency machine.
NEF = 6.75 kW 15 kW = NCT.
9) Basic transition time:
where y1=0 is the value of the tool infeed:
l - the main processing length, l=180 mm;
b) The second transition.
Sharpen the part on top up to Ш49 mm at length l=140 mm, Ra=12.5 µm
The cutting mode is taken according to the first transition.
Main time.
Piece calculation time:
where Tpz=120 - preparatory and final time for the operation;
operational time.
top=Uto+Utv,
Уto=to1+to2=0.82+0.31=1.13 min
where Уtп=20 - auxiliary time for the operation, min;
top=1.13+20=21.13 min
Tshtk= +=28.6 min
c) The third transition.
Drill holes w 14H12 (+0.18) mm to a length l=205 mm, Ra=12 µm
Drilling operation
Equipment
Drilling vertical machine 2H135 specifications listed in Appendix 2.
Cutting tool
1. Drills with diameters: 10 mm according to GOST 2692-92. Drill material high speed steel. Durability of drills Т=45 min. Geometric parameters: 2f=116°; r=2°; w=30°; b=2-5°.
measuring tool
1. Caliper ШЦ-I GOST 166-80, measurement limits 0-125 mm, division value 1 mm, measurement accuracy 0.1 mm.
Cutting data calculation
a) First pass. Drill a hole with a diameter of 10 mm at a length of l = 24 mm, Ra = 12.5 µm.
1) Depth of cut t=0.5d=5 mm.
3) Feed according to the machine passport s=0.25 rpm.
4) Cutting speed V=20 m/min.
5) Spindle speed.
6) Spindle speed according to the passport n=630 rpm.
7) Actual cutting speed:
8) Torque.
Тcr=cm Ddm sqm cr, (2.12)
where cm is the material being processed and the material of the drill taken as a standard, cm = 0.345;
qm - exponent;
mind is an exponent;
kmr - processed material, kmr=1.06.
Tcr=0.345 10I 0.250.8 1.06=12.1 N m
9) Cutting power.
? , (2.5)
where h \u003d 0.75 - efficiency machine.
NE = 0.78 kW 3 kW = NCT.
10) Basic transition time:
where y1=3 is the value of the tool infeed:
l - the main processing length, l=24 mm;
y2 - tool overrun value, y2=0 mm;
Piece calculation time
where T pz \u003d 50 - preparatory and final time for the operation
020 Milling operation
Equipment
Horizontal milling machine X6132
Specifications
Table size (L x W), mm 1320x320
Gap x Width x Number of T-slots, mm x mm x pcs. 18x3
Max. workpiece weight, kg 500
Longitudinal movement, mm 700
Cross movement, mm 255
Vertical movement, mm 320
Longitudinal feed range, mm/min 23.5~1180/18
Cross feed range, mm/min 23.5~1180/1
fixtures
Hydraulic prisms, knives.
Cutting tool
HSS end mill
Number of cutting teeth - 4.
Dimensions: working part diameter - 10 mm
shank diameter - 10 mm
working length - 22 mm
total length - 72 mm.
measuring tool
Metal ruler GOST 427-80, measurement limits 0-40 mm, scale division 1 mm.
Cutting conditions
a) First pass. Mill the part on both sides. Maintain the size l=310 60 mm, Ra=6.3 microns.
1) Depth of cut for end face t = 2 mm.
2) Feed sp = 0.12 mm/rev.
3) Cutting speed v, m/min.
where Cv=330 - takes into account the material being processed and the material of the cutting part of the cutter;
m = 0.2 xV=0.1 yV = 0.2
qv=0,2 - exponents according to the directory
T = 120 - tool life, min;
Kf=0.87 - main angle in plan;
KN=0.90 - state of delivery of the workpiece;
KM = 0.77 - processed material;
Ku =0.65 - material of the cutting part of the cutter;
120.8 m/min
4) Spindle speed.
where D - cutter diameter, D=10 mm
5) Spindle speed according to the passport n=504 rpm.
6) Actual cutting speed:
v===126.6 m/min
7) Minute feed:
sm=sz n Z=0.12 10 504=604.8 mm/min (2.3)
8) Minute feed according to the passport Smin=560 mm/min
9) Actual feed per tooth:
sz===0.06 mm/tooth
10) Cutting force.
where kp=1.31 - processed material.
Cp=8250; Xp=1.0; Yp=0.75; u=1.1; qv=1.3; spr=0.2
11) Feed force.
Px=0.3 Pz=0.3 2235=670.5 N;
Px=670.5 N< 2400 Н = [Рх]
12) Effective cutting power.
where h \u003d 0.75 - efficiency machine.
NEF = 6.2 kW 15 kW = NCT.
13) Basic transition time:
where y1 is the value of the tool infeed:
l - the main processing length, l=80 mm;
y2 - tool overrun value, y2=5 mm;
015 Turning finishing
Equipment
Screw-cutting lathe model 16K20TS.
For technical data, see operation 010.
Cutting tool
Straight line turning cutter, finishing in accordance with GOST 6743-93 type 5, according to the recommendation, the material of the cutting part is T15K6. Tool life T=60 min; ВЧН=16Ч25 - holder section; f1=8; b=8 - back angle; r \u003d 0 - front angle; l \u003d 0 - the angle of inclination of the blade; r = 2 mm - radius at the top of the cutter; f=0.2 mm.
Measuring tool
Metal ruler according to GOST 427-80, measurement limits 0-125 mm, division value 1 mm.
Caliper ШЦ-I according to GOST 166-80, measurement limit 0-125 mm, division value 1 mm, measurement accuracy 0.1 mm
Cutting conditions
Piece calculation time
where Тпз=60 - preparatory and final time for the operation
operational time.
top=Uto+Utv,
where Uto - the sum of the main time, min;
Уto=tо1+tо2+tо3+tо4+tо5=1.13+1.8+0.9+0.71+0.1=4.64 min
where Yt in =24 - auxiliary time for the operation, min;
5. Purpose and device of the machine tool
detail technical axis blank
Consider the machine tool designed within the framework of this course work (Figure 2). The machine fixture is designed for fastening workpieces installed along the outer and inner diameters.
Preliminary adjustment of the cams 15 to a given size is carried out by moving them along the corrugated surface 14. Due to the flat connection of the rod 11 with the clutch 13, the cams can self-adjust, resulting in uniform clamping of the workpiece. The drive is pneumatic.
Three-jaw chuck
Fixture calculation
The initial data for calculating the fixture is the cutting force and torque.
We perform the calculation for operation 010 - turning.
Cutting force = 1060.85 N.
The main component of the cutting force Pz forms the cutting moment.
And the moment of friction Mtr is determined by the formula:
We compose the equation of moments about the x-axis:
We compose the equation of forces about the x-axis:
Lathe setup
Adjustment it includes the setting of the operating chart of adjustment of the specified values of the spindle speed and feed rate when moving the moving parts of the machine (calipers, tables, etc.). For this purpose, the gearboxes and feeds are adjusted. Arrangement (or, if necessary, checking the correct location) of electric, hydraulic and pneumatic stops and converters for controlling the operation of units, installing clamping chucks and reconciling the correct location of the cutting tool (size settings) according to the operational drawing.
In the process of setting up and operating metal-cutting machines, their geometric accuracy (for example, spindle runout) is periodically checked for compliance with the standards specified in the equipment passport.
During the current setup of the machine (sub-adjustment), only a series of transitions indicated above are performed (starting from the fourth, except for the seventh and eighth). The equipment start-up time at the beginning of each shift should be no more than 0.5 hours.
Setting up the milling machine
Adjustment of the milling machine, carry out its preparation for work, which consists of checking the serviceability and readiness of the machine to perform various milling operations. At idle, they check the execution by the machine of commands to start and stop the electric motor, turn the spindle rotation on and off, turn the mechanical table feeds on and off.
After making sure that the machine is working, proceed to its adjustment. We will consider the methods of setting up machines of the milling group using the example of universal console milling machines with manual control.
Drilling machine setup
Before starting work on the drilling machine, it is necessary to make its adjustment.
Setting up the machine means preparatory work for the installation and alignment of the cutting tool and fixtures for fastening workpieces, inspection and trial run of the machine, as well as the selection and installation of the required spindle speed and tool feed rate specified in the technological map or assigned according to special tables. In mass and serial production, the adjustment of machines is usually carried out by highly qualified adjustment workers, in small-scale and individual production, by the drillers themselves.
However, regardless of who set up the machine, before starting work, the machine operator must inspect the machine and test it at idle. In this case, the condition of the spindle should be checked, which should rotate without runout and, like the machine table, move smoothly up and down.
If any malfunctions of the machine are found, they should be reported to the foreman or adjuster.
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Introduction
At this stage of the development of a market economy, much attention is paid to engineering technology.
Mechanical engineering technology is a science that systematizes a set of techniques and methods for processing raw materials and materials with appropriate production tools in order to obtain finished products. The subject of study in mechanical engineering is the manufacture of products of a given quality with an established production program at the lowest cost of materials, minimum cost and high labor productivity.
The technological process in mechanical engineering is characterized not only by the improvement of the design of machines, but also by the continuous improvement of their production technology.
At present, due to the high level of development of electronics in mechanical engineering, CNC machines are widely introduced. The use of such equipment makes it possible to reduce: metalwork and finishing work; preliminary markup; production preparation time, etc.
Given all this, I widely use CNC machines, and in the graduation project, a number of tasks are considered necessary to complete the task for the graduation design.
These tasks include:
Raising the technical level of production;
Mechanization and automation of production;
Development of a progressive technological process for processing the “Axis” part;
Development of measures to further increase savings in fixed assets, product quality and reduce the cost of manufacturing parts.
The correct solution of all the above tasks allows you to get:
Growth in labor productivity;
The release of part of the workers;
Increase in annual economic effect;
Reducing the payback period of additional costs.
1 . Technological part
1.1 Description of working conditions, service purpose of the part, analysis of manufacturabilitydetails and the feasibility of transferring its processing to CNC machines
Detail: "Axis" No. B. 5750.0001
It is an integral part of the stabilizer drive mechanism. The drive rocker rotates on the axis, therefore Xtv is applied on the surface of Ш40f7. 48-80, SH24H9 hole for special fixing bolt H. 5750.0001. For fixing with a special fastening bolt, grooves 20H11 are made, as well as 3 holes Ш1.5 are made for locking (locking) 2.2 OST 139502.77, cotter pin 2.5x 32.029 GOST 397-79.
The manufacturability of the design of the part is evaluated by qualitative parameters and quantitative indicators.
Qualitative assessment of the manufacturability of the design
1 Detail "Axis" of the correct geometric shape and is a body of revolution.
2 The material of the part (steel 30KhGSA GOST 4543-71) has good machinability.
3 Possibility of using a blank-forging, the geometric shape and dimensions of which provide small allowances for machining.
4 The presence of unified elements of the part confirms the manufacturability of its design.
5 The design of the part has sufficient rigidity, since the condition
6 The configuration, accuracy and roughness of the surfaces make it possible to process the part on standard equipment of normal accuracy and using standard cutting tools.
Table 1.1 - Dimensional accuracy and surface roughness parameter of the part
|
Surface dimensions |
Quality of accuracy |
Roughness parameter |
Number of structural elements |
Number of unified elements |
|
Quantification of the manufacturability of the design
1 Coefficient of unification:
where Que - the number of unified elements;
Qe - the number of structural elements.
2 Accuracy factor of part surfaces:
where Ti - respectively the quality of the accuracy of the processed surfaces;
Tav. - the average value of these parameters;
ni - number of dimensions or surfaces for each quality
3 Coefficient of surface roughness of parts:
where Rai - respectively, the values of the roughness parameters of the treated surfaces;
Raav. - the average value of these parameters;
ni is the number of dimensions or surfaces for each value of the roughness parameter.
Conclusion: from the above calculated coefficients, it can be seen that the numerical values of almost all manufacturability indicators are close to 1, i.e. the manufacturability of the design of the part satisfies the requirements for the product. It is expedient to process the “Axis” part on machines with numerical control, since the part is well processed by cutting and is conveniently based.
1.2 Chemical composition andmechanical properties of the materialdetails
Detail "Axis" is made of steel 30HGSA - structural alloyed steel that can withstand significant deforming loads.
It is recommended to manufacture from steel 30KhGSA: shafts, axles, gears, flanges, casings, blades of compressor machines operating at temperatures up to 2000C, levers, pushers, critical welded structures operating under alternating loads, fasteners operating at low temperatures.
Data on the chemical composition and mechanical properties of the material are placed in tables from the relevant sources.
Table 1.2 - Chemical composition of steel
Table 1.3 - Mechanical properties of steel
|
Section, mm |
||||||||
Technological properties
Weldability - limited weldability.
Welding methods: RDS; ADS submerged and gas shielded, ArDS, EShS.
Machinability - in a hot-rolled state at HB 207h217 and w = 710 MPa.
Floken sensitivity - sensitive.
Tendency to temper brittleness - prone.
1.3 Determining the type of production
In mechanical engineering, the following types of production are distinguished:
Single;
Serial (small-scale, medium-scale, large-scale);
Bulk.
Each type of production is characterized by the coefficient of consolidation of the operation Kz.o.
Coefficient of consolidation of operations Кз.о. is determined by the formula:
where Qop. - the number of different operations performed on the site;
Pm is the number of workplaces (machines) on which these operations are performed.
According to GOST 3.1108-74, the coefficient of consolidation of operations is taken equal to
Table No. 1.4 - The value of the coefficient of consolidation of operations
From the above calculated it follows that the production is serial, it is necessary to determine the batch of parts to be launched. Approximately the size of the batch can be calculated by the formula:
where N is the annual output, pieces;
The number of working days in a year (365-Tout. - Thol.), days;
Required stock of parts in stock in days, fluctuates between 3h8 days
for single and small-scale production 3h4 days
for medium batch production 5h6 days
for large-scale and mass production 7h8 days
Serial production is characterized by a limited range of products manufactured or repaired in periodically repeated batches, and by relatively large output volumes.
In serial production, universal machines are widely used, as well as specialized and partially special machines.
The equipment is located not only on a group basis, but also along the flow.
Technological equipment is universal, as well as special and universal-assembly, which reduces the complexity and cost of manufacturing the product.
Workers specialize in only a few tasks. The technological process is differentiated, i.e. divided into separate independent operations, transitions, techniques, movements.
The cost of the product is average.
1.4 Factory Process Analysis
Each part must be manufactured with minimal labor and material costs. These costs can be reduced to a large extent from the correct choice of the technological process option, its equipment, mechanization and automation, the use of optimal processing modes and proper production preparation. The labor intensity of manufacturing a part is particularly influenced by its design and technical requirements for manufacturing.
In the factory workflow, the “Axis” part is processed as follows:
005 Control 065 Locksmith
010 Turning 070 Marking
015 Turning 075 Drilling
020 Turning 080 Washing
025 Control 085 Magnetic
030 Thermal 090 Control
035 Sandblasted 095 Coated
040 Turning 100 Grinding
045 Sanding 105 Locksmith
050 Turning 110 Washing
055 Marking 115 Magnetic
060 Milling 120 Preparatory
As can be seen from the above listed operations of the factory technological process, a large number of control, plumbing, marking operations are used here, and old-fashioned universal machines with manual control are used.
I believe that in my version of the technological process for processing the “Axis” part, it is necessary to use high-performance CNC machines for some operations, which will allow:
Increase labor productivity;
Eliminate marking and locksmith operations;
Reduce the time for equipment readjustment, for the installation of blanks through the use of universal assembly fixtures;
Reduce the number of operations;
Reduce the cost of time and money for the transportation and control of parts;
Reduce marriage;
Reduce the need for labor force;
Reduce the number of machines;
Apply multi-station service;
In addition, in horizontal milling and vertical drilling operations, it is advisable to use special quick changeover devices with a pneumatic clamp, which ensure reliable fastening and precise locating of the part during processing, and will also allow:
Reduce time for equipment changeover;
Ensure a fixed and reliable position of the workpiece in the fixture;
Free from pre-marking before this operation
The use of a special high-performance cutting tool ensures high accuracy and the necessary roughness of the machined surfaces.
1.5 Technical and economic assessment of the choice of method for obtaining a workpiece
The choice of a method for obtaining a workpiece is one of the most important factors in the design and development of a technological process.
The type of workpiece and the method is largely determined by the material of the part, the type of production, as well as such technological properties as the structural shape and overall dimensions of the part.
In modern production, one of the main directions in the development of machining technology is the use of finished workpieces with economical structural forms, i.e. it is recommended to shift most of the part shaping process to the procurement stage and thereby reduce costs and material consumption during machining.
In the thesis for the part "Axis" I use the method of obtaining a workpiece - hot stamping on crank presses.
With this method, the shape of the workpiece is close in size to the dimensions of the part, and this reduces the consumption of material and the time for manufacturing the “Axis” part, as well as the number of machining operations and, consequently, the cost of this part.
1.6 Selection of technological bases
A base is a surface that replaces a set of surfaces, an axis, a point of a part in relation to which other parts being machined in this operation are oriented.
To improve the accuracy of processing a part, it is necessary to observe the principle of combination (unity) of bases, according to which, when assigning technological bases for precise machining of a workpiece, surfaces that are simultaneously design and measurement bases of a part should be used as technological bases.
As well as the principle of constancy of bases, which lies in the fact that when developing a technological process, it is necessary to strive to use the same technological base, without allowing a change in technological bases without the need.
The desire to carry out processing on one technological base is explained by the fact that any change of bases increases the error in the relative position of the processed surfaces.
After analyzing all of the above, I conclude that in order to process the “Axis” part, it is necessary to take for the base surfaces:
Operation 010 Turning CNC
Set A: 61.8
Set B: ? 40.3
: ?40,3
: ?40,3
Operation 025 Cylindrical grinding: holes. Ш24H9
1.7 Design of the route technological process of the part: processing sequence; choice of equipment; choice of machine tools; choice of cutting tools; select op auxiliary tools
When developing a technological process, they are guided by the following basic principles:
First of all, I process those surfaces that are basic for further processing;
After that, surfaces with the largest allowances are processed;
Surfaces, the processing of which is due to the high accuracy of the relative position of the surfaces, must be processed from one installation;
When processing precise surfaces, one should strive to observe two main allowances: the combination (unity) of the bases and the constancy of the bases
Processing sequence
Operation 005 Procurement
Operation 010 Turning CNC
Set A
Install, fix the workpiece
1 Sharpen the end “clean”
2 Sharpen a chamfer 1x450
3 Sharpen Ш40.4 mm at l=63.5-0.2 mm, holding R1
4 Sharpen a chamfer 1x450
5 Countersink chamfer 1x450
Set B
Reinstall, fix the workpiece
1 Sharpen the end “cleanly” after holding l = 79.5-0.2 mm
2 Sharpen a chamfer 1x450
3 Sharpen Ø60 mm per pass
4 Countersink Ø23.8 mm per pass
5 Countersink chamfer 2.5x450
6 Expand Ш24H9 (+0.052)
7 Control by the contractor
Operation 015 Horizontal milling
Set A
Install, fix the part
1 Mill the groove B=20H11 (+0.13) at l=9.5 mm, maintaining R1
Set B
Reinstall, fix part
1 Mill groove B=20H11 (+0.13) at l=41 mm
2 Blunt sharp edges, saw 2 chamfers 0.5x450; 2 chamfers 1x450
3 Control by the performer
Operation 020 Vertical drilling
Install, fix the part
1 Drill 3 holes. Ш1.5 mm per passage, bearing? 1200, l=48 mm
2 Drill 3 chamfers 0.3x450
3 Control by the performer
Operation 025 Thermal
1 Heat 35.5…40.5 HRC
Install, fix the part
1 Grind Ø40f) at l=60 using the cross feed method
2 Control by the performer
Operation 035 Control
Equipment selection
When choosing equipment, the following factors are taken into account:
type of production;
Type of workpiece;
Requirements for machining accuracy and surface roughness;
Required power;
Annual program.
Based on the above, I choose technological equipment.
Operation 010 CNC Turning
CNC screw-cutting lathe 16K20F3
The machine is designed for turning the outer and inner surfaces of parts with a stepped and curvilinear profile in axial section with a semi-automatic cycle specified by the program on a perforated tape.
|
Options |
Numeric values |
|
|
The largest diameter of the processed workpiece: |
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above bed |
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above the caliper |
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The largest diameter of the bar passing through the spindle hole |
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The greatest length of the processed workpiece |
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Thread pitch: |
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Metric |
||
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Number of spindle speeds |
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The largest movement of the caliper: |
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|
longitudinal |
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|
transverse |
||
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Caliper feed, mm/rev (mm/min): |
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|
longitudinal |
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|
transverse |
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|
Number of feed steps |
||
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Fast movement speed of the caliper, mm/min: |
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|
longitudinal and transverse |
||
|
vertical |
||
|
Power of the electric motor of the main drive, kW |
||
|
Overall dimensions (without CNC): |
||
|
weight, kg |
Operation 015 Horizontal milling
Horizontal milling universal machine 6Р81Ш /10/
The machine is designed to perform various milling operations, as well as drilling and simple boring operations in workpieces made of cast iron, steel and non-ferrous metals. The machine can operate in semi-automatic and automatic modes, which makes it possible to use multi-machine equipment.
Machine Specifications
|
Options |
Numeric values |
|
|
Working surface dimensions (width x length), mm |
||
|
The greatest movement of the table; mm: |
||
|
longitudinal |
||
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transverse |
||
|
vertical |
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Distance: |
||
|
from the axis of the axis of the horizontal spindle to the table surface |
||
|
from vertical spindle axis to bed rails |
||
|
from the end face of the vertical spindle to the surface of the table |
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The greatest movement of the sleeve of the vertical spindle, mm |
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|
Angle of rotation of the vertical milling head, in a plane parallel to: |
||
|
longitudinal course of the table |
||
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transverse course of the table: |
||
|
from the bed |
||
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to the bed |
||
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Spindle inner taper according to GOST 15945-82: |
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horizontal |
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vertical |
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Number of spindle speeds: |
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horizontal |
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vertical |
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Spindle speed, rpm: |
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horizontal |
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vertical |
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Number of table feeds |
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Table feed, mm/min: |
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|
longitudinal |
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transverse |
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vertical |
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Speed of fast movement of a table, mm/min: |
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|
longitudinal |
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transverse |
||
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vertical |
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Dimensions: |
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|
Weight (without remote equipment), kg |
Operation 020 Vertical drilling
Vertical drilling machine 2H125
The machine is designed for drilling, reaming, countersinking, reaming holes, tapping and cutting ends with knives.
|
Options |
Numeric values |
|
|
The largest nominal drilling diameter, mm |
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Table top |
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The greatest distance from the end face of the spindle to the working surface of the table |
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spindle overhang |
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Spindle stroke |
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Maximum vertical movement: |
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drilling head |
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Morse taper spindle bore |
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Number of spindle speeds |
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|
Spindle speed, rpm |
45; 63; 90; 125; 180; 250; 355; 500; 710; 1000; 1400; 2000 |
|
|
Number of spindle feeds |
||
|
Spindle feed, mm/rev |
0,1; 0,14; 0,2; 0,28; 0,4; 0,56; 0,8; 1,12; 1,6 |
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Main drive motor power movement, kW |
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Machine efficiency |
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Overall dimensions, mm: |
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weight, kg |
Operation 030 Cylindrical Grinding
Cylindrical semi-automatic machine for plunge and longitudinal grinding, increased accuracy 3M151
The machine is designed for external grinding of cylindrical and gently sloping conical surfaces.
|
Options |
Numeric values |
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|
The largest dimensions of the workpiece to be installed: |
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Maximum grinding length: external |
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Center height above table |
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The greatest longitudinal movement of the table |
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Angle of rotation in about: |
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clockwise |
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counterclock-wise |
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Table automatic movement speed (stepless regulation), m/min |
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Workpiece spindle speed with stepless regulation, rpm |
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Morse taper of headstock spindle and tailstock quill |
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The largest dimensions of the grinding wheel: |
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outside diameter |
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Headstock movement: |
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greatest |
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one division of the limbus |
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per turn of the push handle |
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Grinding wheel spindle speed, rpm |
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when grinding external |
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Infeed feed rate of the grinding headstock, mm/min |
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Main drive electric motor power, kW |
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Overall dimensions, mm: |
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|
weight, kg |
Choice of machine tools
When developing a technological process for machining a part, it is necessary to choose the right device, which should help increase labor productivity, processing accuracy, improve working conditions, eliminate preliminary marking of the part and align it when installed on the machine.
Operation 010 Turning CNC
Attachment: three-jaw self-centering chuck
GOST 2675-80 is included with the machine; center rotating
GOST 2675-80.
Operation 015 Horizontal milling
Attachment: Special setting fixture for milling a part with built-in pneumatic cylinder.
Operation 020 Vertical drilling
Attachment: Universal dividing head GOST 8615-89;
hard cent GOST 13214-79.
Operation 030 Cylindrical Grinding
Attachment: driver chuck for grinding work
GOST 13334-67 Clamp for grinding work
GOST 16488-70
Choice of cutting tool
When choosing a cutting tool, it is necessary to strive to accept a standard tool, but sometimes it is advisable to take a special, combined or shaped tool that allows you to combine the processing of several surfaces.
The correct choice of the cutting part of the tool is also of great importance for increasing labor productivity, improving the accuracy and quality of the machined surface.
Operation 010 CNC Turning
Set A
Transition 01, 02, 03, 04 Through thrust cutter with plates made of hard alloy T15K6, 16x25 GOST 18879-73 /7/
Set B
Transition 01, 02, 03 Through-thrust bent cutter with hard-alloy plates T15K6, 16x25 GOST 18879-73
Technical characteristics of the cutter: H=25 mm, H=16 mm, L=140 mm, n=7 mm, l=16 mm, r=1.0 mm.
Transition 04 Solid drill Ø23.8 mm made of R6M5 high-speed steel with a tapered shank GOST 12489-71
Technical characteristics of the countersink: D=23.8 mm, L=185 mm, l=86 mm.
Transition 05 Countersink?450 from R6M5 high speed steel with OST-2 tapered shank
Countersink technical characteristics: D=32 mm, L=145 mm, l=56 mm.
Transition 06 Reamer made of high-speed steel one-piece Sh24H9 (+0.052) with a tapered shank GOST 1672-80
Technical characteristic of the reamer: D=24 mm, L=225 mm, l=34 mm
Operation 015 Horizontal milling
Transition 01 Three-sided disk cutter Sh125 with insert knives equipped with hard alloy T15K6, z=8 GOST 5348-69
Technical characteristics of the cutter: D=100 mm, B=20 mm, d=32 mm, z=8 mm.
Transition 02 Needle file flat GOST 1513-77
Technical characteristics of the cutter: L=130 mm.
Operation 020 Vertical drilling
Transition 01 Spiral drill? 1.5 mm from R6M5 high-speed steel with a cylindrical shank GOST 10902-77
Technical characteristics of the drill: d=1.5 mm, L=63 mm, l=28 mm.
Transition 02 Spiral drill? 6 mm from R6M5 high-speed steel with a cylindrical shank GOST 10902-77
Drill Specification: d=6mm, L=72mm, l=34mm
Operation 030 Cylindrical Grinding
Transition 01 Grinding wheel 300x63x76 PP 24A40NSM25K8
GOST 2424-83.
Technical characteristics of the circle: D = 300 mm, B = 63 mm, d = 76 mm.
1.7.5 Selecting an auxiliary tool
When choosing auxiliary tools, they use the same principles as machine tools.
Based on the above, I make a choice of auxiliary tools.
On Operation 010 Turning CNC:
Set A
Transition 05 - I use the adapter sleeve GOST 13598-85
Set B
Transition 04, 05, 06 - I use the adapter sleeve GOST 13598-85.
1.8 Determination of operating allowances, tolerances, interoperationaldimensions and dimensions of the workpiece (for twosurface producecalculation of allowances by the analytical method)
The choice of a workpiece for further machining and the establishment of rational allowances and tolerances for processing is one of the very important stages in the design of the technological process for manufacturing a part. From the correct choice of the workpiece, i.e. establishing its shape, size, processing allowances, dimensional accuracy and hardness of the material to a greater extent depends on the nature and number of operations or transitions, the complexity of manufacturing the part, the amount of material and tool consumption, and, as a result, the cost of manufacturing the part.
Determination of allowances by the analytical method
The analytical method for determining allowances is based on the analysis of production errors that occur under specific conditions for processing the workpiece.
For external or internal surfaces of bodies of revolution, operating allowances 2Zi min µm are determined by the formula:
where is the height of surface microroughnesses;
Depth of the surface defective layer;
The total value of spatial geometric deviations;
Installation error
We determine intermediate allowances and intermediate dimensions when machining the hole surface? 24H9 (+0.052).
For clarity and ease of determining intermediate allowances and sizes, we compile a table.
Table 1.5 - Calculations of allowances, tolerances and intermediate dimensions for a given surface
|
The surface of the part and the route of its processing |
Size tolerance, mm |
allowance elements, |
Intermediate allowances, mm |
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Blank-stamping |
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Single boring |
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|
Threading |
Check: Tdzag - Tdd =
1400 - 62 = (3758+352) - (2488 + 284)
1338 µm = 1338 µm
Rice. 1.1 - The layout of the fields of allowances and tolerances on the machined surface
We determine intermediate allowances and intermediate dimensions when processing the surface of the shaft? 40f7.
For clarity and ease of determining intermediate allowances, tolerances and sizes, we compile a table /10/
Table 1.6 - Calculations of allowances, tolerances and intermediate dimensions for a given surface
|
Type of blank and technological operation |
Workpiece and surface accuracy |
Size tolerance, mm |
Allowance elements, microns |
Intermediate blank dimensions, mm |
Intermediate allowances, mm |
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|
Blank-stamping |
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|
Rough turning |
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|
Fine turning |
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|
Heat treatment grinding |
Check: Tdzag - Tdd =
1400 - 25 = (2818+468+54) - (1668+257+40)
1375 µm = 1375 µm
Rice. 1.2 - The layout of the fields of allowances and tolerances on the machined surface
Calculation of allowances, tolerances, interoperational dimensions in a tabular way
For the remaining surfaces of the workpiece, allowances, tolerances, interoperational dimensions are considered in a tabular way, I summarize the data obtained in a table
Table 1.7 - Calculation of allowances, tolerances and intermediate dimensions for other surfaces
|
Subsequence processing |
Quality of accuracy |
Roughness |
Tolerances mm |
Allowance amount |
Estimated size, mm |
Limit size, mm |
Limit allowance, mm |
|||
|
Blank-stamping Single semi-clean turning l=79.5 |
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|
Blank-stamping Single semi-clean turning?60 |
Table 1.8 - Interoperational dimensions of workpiece surfaces
1.9 Definition of the normconsumption (calculate material utilization and workpiece utilization)
To determine the material consumption rate, it is necessary to determine the mass of the workpiece. The mass of the workpiece is calculated based on its volume and density of the material. It is necessary to strive to ensure that the shape and dimensions of the workpiece are close to the shape and dimensions of the finished part, which reduces the complexity of machining, reduces the consumption of material, cutting tools, electricity, etc.
The mass of the workpiece is calculated by the formula:
where is the density of the material, g/cm3
The total volume of the workpiece, cm3.
Usually, a complex figure of a workpiece must be divided into elementary parts of the correct geometric shape and the volumes of these elementary parts must be determined. The sum of elementary volumes will be the total volume of the workpiece.
The volume of a cylindrical pipe V, cm3 is calculated by the formula:
where is the outer diameter of the cylindrical pipe, cm
Internal diameter of a cylindrical pipe, cm
h is the height of the cylindrical pipe, cm.
The correct choice of the method for obtaining the workpiece is characterized by two factors:
Kim - material utilization rate
Kiz - workpiece utilization rate
where is the mass of the part, g
where is the mass of metal losses (waste, flash, on a segment, etc.)
The material utilization factor varies within the following limits:
For casting 0.65 h 0.75…0.8
For punching 0.55h 0.65…0.75
For rental 0.3h 0.5
Having calculated the material utilization factor and the workpiece utilization rate, I conclude that these coefficients are within acceptable limits, therefore, the chosen method for obtaining the workpiece is correct.
1.10 Determination of cutting conditions, power for two
Determining cutting conditions and power can be done in two ways:
Analytical (according to empirical formulas);
Tabular
Calculation of cutting conditions for two different operations or transitions using empirical formulas
We calculate cutting conditions and power for diverse operations and transitions using empirical formulas
Operation 010 Turning CNC
Set B
Transition 01 Sharpen the end “cleanly” after holding l = 79.5-0.2 mm
Depth of cut: t=1.0 mm
Feed: S=0.5 mm/rev /10/
Cutting speed V, m/min:
where Cv = 350; x=0.15; y=0.35; m=0.2 /7/
T - tool life, min (T=60 min)
Kv = Kmv Knv Kuv KTv KTc Kc Kr
where Kf - coefficient characterizing the steel group in terms of machinability
Knv - coefficient taking into account the influence of the state of the surface of the workpiece on the cutting speed (Knv=0.8) /9/
Кuv - coefficient taking into account the influence of tool material on cutting speed (Кuv=1.15) /9/
KTv - coefficient taking into account tool life depending on the number of simultaneously working tools (KTv=1.0)/9/
КТс - coefficient taking into account tool life depending on the number of simultaneously serving machines (КТс=1.0)
Kc - coefficient taking into account the influence of the main angle in terms of c (Kc = 0.7)
Kr - coefficient taking into account the influence of radius r at the tip of the cutter (Kr=0.94) /9/
Kv = 0.56 0.8 1.15 1.0 1.0 0.7 0.94 ? 0.34
Workpiece rotation frequency, n rpm:
where V - cutting speed, m/min
D - diameter of the processed surface, mm
According to the processing conditions, we accept:
npr = 359 rpm
Cutting force, PZ N:
PZ = 10 Cp tx Sy Vn Kp
where Cp = 300; x=1.0; y=0.75; n= -0.15 /7/
Kp - coefficient affecting the cutting force
Kp = Kmp Ktp Kp Kp Krp
where n is the exponent (n=0.75) /9/
Kcr - coefficient taking into account the influence of the main angle in the plan
on cutting force (Кcr=0.89) /9/
Kp - coefficient taking into account the influence of the rake angle on the cutting force (Kp=1.0) /9/ Kp - coefficient taking into account the influence of the angle of inclination of the main blade on the cutting force (Kp =1.0). Krp - coefficient taking into account the influence of the radius at the top on the cutting force (Krp=0.87).
Kr = 1.31 0.89 1.0 1.0 0.87? 1.01
Hence the cutting force PZ N:
PZ = 10 300 1.01.0 0.50.75 70-0.15 1.01? 947 N
Minute feed Sm, mm/min
where So - feed per workpiece revolution, mm/rev;
npr - the accepted frequency of rotation of the workpiece rpm
Sm = 0.5 359? 180 mm/min
Effective cutting power Ne, kW:
where - cutting force, N
Cutting speed, m/min
The effective power is calculated correctly if the following condition is met: 1.08 kW 10 0.75
1.08 kW 7.5 kW
Operation 015 Horizontal milling
Transition 01 Mill times in dimension 20H
Cutting depth: 9mm
Milling width B = 20 mm
Submission: Sz. =0.06 mm/tooth /10/
Cutting speed V, m/min:
where Cv = 690; m = 0.35; x = 0.3; y=0.4; u = 0.1; p = 0 /5/
T - cutter durability, min (T=120 min); /7/
B - milling width, mm. B=20mm
Kv - coefficient affecting the cutting speed
Kv = Kmv Kuv Klv
where Kmv is a coefficient that takes into account the influence of the physical and mechanical properties of the material being processed on the cutting speed
where Kf - coefficient characterizing the steel group in terms of machinability (Kf = 0.8)
nv - exponent (nv=1.0)
Кuv - coefficient taking into account the influence of tool material on cutting speed (Кuv=1.0)
Kv = 0.54 0.8 1.0? 0.5
Hence the cutting speed V, m/min:
Spindle speed, n rpm:
where the designations are the same
nd=500 rpm
Actual cutting speed Vd, m/min:
where the designations are the same
Minute feed Sm, mm/min:
where the designations are the same
Sm =0.06 8 500=240 mm/min
According to the processing conditions and passport data of the machine, I accept:
Sm = Sv =200 mm/min, then the actual feed per tooth of the cutter is:
Cutting force, Pz N:
where Cp = 261; x = 0.9; y=0.8; u = 1.1; = 1.1; w = 0.1 /7/
where Kp is the coefficient affecting the cutting force
where Kmp is a coefficient that takes into account the influence of the quality of the material being processed on the cutting force
where n is the exponent (n=0.3) /9/
kmp=? 1.12 Hence the cutting force, Pz N:
Cutting power Nrez, kW:
where the designations are the same
Checking if the drive power of the machine is sufficient
Power on the spindle of the machine N_ (shp,)
where the designations are the same
The effective cutting power is calculated correctly if the following condition is met:
3.56 kW 6 Therefore processing is possible.
Calculation of cutting conditions and power for other operations and transitions according to current standards For the convenience of further use of the calculated cutting conditions, we compile a table
Table 1.9 - Calculation of cutting conditions for the operations of the technological process
|
Depth of cut, mm |
Feed S mm/rev SZ mm/tooth |
Cutting speed V, mm/min |
Speed n, rpm |
Actual cutting speed Vph m/min |
Minute feed Sm mm/min |
Cutting power Nr, kW |
|
|
Operation 010 Turning CNC Transition 01 Sharpen the end "clean" |
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|
Transition 02 Chamfering 1x450 |
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|
Transition 03 Sharpen Ш40.4 mm at l=63.5-0.2 mm, keeping R1 |
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|
Transition 04 Chamfering 1x45o |
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|
Transition 05 Reaming chamfer 1x45o |
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|
Set B Transition 02 Chamfering 1x45o |
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|
Transition 03 Sharpen Ø60 mm per pass |
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|
Transition 04 Reaming Ø23.8 mm per pass |
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|
Transition 05 Countersink chamfer 2.5x450 |
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|
Transition 06 Expand Sh24H9 (+0.052) |
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|
Operation 020 Vertical drilling Transition 01 Drill 3 holes. Ш1.5 mm per passage, bearing? 1200, l=48 mm |
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|
Transition 02 Drill 3 chamfers 0.3x450 |
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|
Operation 030 Cylindrical Grinding Transition 01 Grind Ø40f) at l=60 mm using the cross feed method |
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1.11 Determination of time norms for operations
The technical norm of time for processing the workpiece is the main parameter for calculating the cost of the manufactured part, the number of production equipment, wages and production planning. The technical norm of time is determined on the basis of the technical capabilities of technological equipment, cutting tools, machine tools and the proper organization of the workplace.
Determination of time standards for an operation performed on a CNC machine
Operation 010 Turning CNC
1 Time of automatic operation of the machine Ta, min:
Ta = Toa + Twa
where Toa - the main time of automatic operation of the machine, min;
Tva - auxiliary time of the machine according to the program, min.
where l is the length of the machined surface in the feed direction, mm;
l1 - infeed value, mm;
l2 - overrun value, mm;
S - feed per revolution of the part, mm / rev;
i - number of passes.
Toa = 0.06+0.03+0.25+0.03+0.02+0.03+0.12+0.41+0.71+0.03 = 1.69 min
Tva = Tvha + Toast
where Twha - the time of execution of automatic auxiliary moves (supply of a part or tool from the starting points to the processing zones and retraction, setting the tool to a size), min;
where dxx - idle length, mm;
Sxx - idle speed, m/min;
Number of technological sites.
Toast - time of technological pauses (stops, supply of spindle rotation to check dimensions, inspection or tool change), min
where a is the number of stops
2 Auxiliary manual work time TV, min:
where a=0.0760; x = 0.170; y = 0.15
Auxiliary time associated with the operation, min
where a=0.36; b=0.00125; c=0.04; d=0.022; =0
Xо Yо Zо - zero coordinates;
k - number of correctors in adjustment;
lpl - length of punched tape, m (lpl = 0.5 m)
Auxiliary time overlapped for control measurements of the part, min
where k = 0.0187; z = 0.21; u = 0.330 /11/
D - measured diameter, mm
L - measured length, mm
TV \u003d 0.25 + 0.58 + 0.16 \u003d 0.99 min
3 Preparatory and final time Tpz, min:
Tpz = a + b nu + c Pp + d Pnn
where a = 11.3; c = 0.8; c = 0.5; d=0.4
nu - number of cutting tools;
Рр - the number of established initial modes of operation of the machine (Рр=2);
Pnn - number of sizes dialed by switches on the control panel (Pnn = 2 h 3)
T nz \u003d 11.3 + 0.8 4 + 0.5 2 + 0.4 3 \u003d 16.7 min
After determining TV, it is adjusted depending on the serial production.
4 Seriality correction factor:
where a=4.17; x = 0.216;
where npr is the production batch of parts, pcs. (section 1.4)
5 Piece time Tsht, min:
where (aorg + aotl) - the percentage of time spent on organizational and maintenance of the workplace and recreation (aorg + aotl) = 10% /2/
Batch processing time:
where the designations are the same
T \u003d 3.44 280 + 16.7 \u003d 980 min
Determination of time standards for operations performed on universal machines
Operation 015 Horizontal milling
Set A
Transition 01
where L is the path traveled by the tool, mm:
where l is the length of the treated surface, mm;
l1 - value of tool penetration, mm;
l2 - the value of the overrun of the tool, mm;
n is the frequency of rotation of the part, rpm;
i - number of passes.
where - auxiliary time for installation and removal of the part, min
Auxiliary time associated with the transition, min
Auxiliary time associated with control measurements, min
Set B
Transition 01
1 The main operating time of the machine To, min:
Auxiliary time TV, min:
where the designations are the same
Toper = 0.48 + 1.0 = 1.48 min
Tobs =3.5% of Toper
Totl = 4% of Toper
where K is the total percentage of time for servicing the workplace and time for rest and personal needs
where - preparatory and final time for setting up the machine, tools and fixtures, min
Preparatory-final time for additional receptions, min
Preparatory and final time to receive tools and accessories before the start and hand them over after the end of processing, min
Operation 020 Vertical drilling
Transition 01
1 The main operating time of the machine To, min:
2 Auxiliary time TV, min:
Transition 02
1 The main operating time of the machine To, min:
2 Auxiliary time TV, min:
3 Operative time Toper, min:
Toper = 0.93 + 0.79 = 1.72 min
4 Time to service the workplace Tobs, min:
Tobs =4% of Toper
5 Time for rest and personal needs Totl, min:
Totl = 4% of Toper
6 Standard piece time Tsht, min:
7 Preparatory and final time Tpz, min:
8 Piece-calculation time Tshk, min:
Operation 030 Cylindrical Grinding
Transition 01
1 The main operating time of the machine To, min:
where is the length of the table travel, mm/dv. move
Machining allowance per side, mm
Minute longitudinal feed, mm/min
Cross feed, mm/rev
2 Auxiliary time TV, min:
3 Operative time Toper, min:
Toper = 0.3+ 0.81= 1.11 min
4 Time to service the workplace Tobs, min:
Tobs =9% of Toper
5 Time for rest and personal needs Totl, min:
Totl = 4% of Toper
6 Piece time Tsht, min:
7 Preparatory - final time Tpz, min:
8 Piece-calculation time Tshk, min:
For the convenience of further calculations, all the data obtained are summarized in a table.
Table 1.10 - Time standards for all operations of the technological process
Calculation and coding of programs for given operations
Based on all the above calculations, I calculate and code the control program for operation 010 CNC Turning.
Table 1.11 - Tool path
According to the compiled tabular data, I encode the program:
Set A
Set B
Program control
When preparing a program, as a rule, errors occur that are corrected in the process of debugging and implementing the program.
Errors occur when setting the initial data in the process of calculating and writing the UE to the program carrier. Accordingly, geometric, technological and perforation errors or recording errors on magnetic tape are distinguished.
Geometric errors appear when the dimensions of a part, workpiece, etc. are incorrect. To detect geometric errors, various types of graphic devices are used, for example, coordinate and graphic displays. Technological errors are associated with the continuous selection of the cutting tool, cutting modes, sequence of processing the part on the machine. Errors in writing a program to a program carrier appear due to incorrect actions of technologists when stuffing information or as a result of malfunctions in the data preparation device. These errors appear in the process of controlling the control program on the coordinator or on CNC machines.
2 . Design part
2.1 Description of the design and calculation of the machine tool
The purpose of the device and the principle of operation of the designed device
The dividing head with a collet clamp is designed for grooving during the milling operation of parts of the “Axis” type.
The principle of operation of the device is as follows: Compressed air from the network through the fitting (19) is supplied to the pneumatic cylinder (20) formed in the body of the device and acts on the piston (22). The resulting force is transmitted through the thrust ball bearing (37) to the three pins (25) which lift the cup (4) placed in the steel guide sleeve (7).
Rising, the glass with a conical hole compresses the cone of the collet (5). The workpiece is then fixed.
When the air supply is turned off, the fingers (9) under the action of the spring (8) return the glass to its original position.
To move to the next position, the collet together with the workpiece is turned with the handle (29). To move clockwise, the eccentric disk (27) pushes the latch (14) out of the groove of the dividing disk (28), and the pawl (30) under the action of the spring (31) enters its next groove.
When the handle (29) moves back, the pawl (30) turns the dividing disk (28) with the disk (3) and the collet (5) mounted on it with the workpiece until the lock (14) falls into the next groove of the dividing disk and thereby not fixing the rotation of the part by 900.
The cap (6) protects the slots of the collet from chips during milling.
Calculation and accuracy
The basing error is the deviation of the actually achieved position, it is defined as the limiting stray field, the distance between the technological and measuring bases in the direction of the maintained size.
The total error in any machining operation consists of:
1 workpiece installation error;
2 machine setting error
3 processing error that occurs during the manufacturing process of the part. The value of the basing error is determined by the following calculations:
where is the error of setting the workpiece;
Machine setting error;
Machining error that occurs during the manufacturing process of the part;
d - size tolerance.
The installation error is one of the components of the total error of the performed part size. It occurs when the workpiece is installed in the fixture and consists of the locating error, the fixing error and the position error of the workpiece, which depends on the accuracy of the fixture and is determined by errors in the manufacture and assembly of its installed elements and their wear during operation.
The machine setting error occurs when the cutting tool is set to the size, as well as due to the inaccuracy of the copiers and stops for automatically obtaining the size on the part.
The processing error that occurs during the manufacture of the part on the machine is explained by:
1 Geometric inaccuracy of the machine;
2 Deformation of the technological system under the action of cutting forces;
3 Inaccuracy in the manufacture and wear of the cutting tool and fixture.
4 Temperature deformations of the technological system.
EU \u003d 0.02 + 0 + 0.03 \u003d 0.05 mm
0.05+0.03+0.03? 0.13mm
0.11 mm? 0.13mm
Determining clamping force
To determine the clamping force, it is necessary to calculate the cutting force for the operation for which the fixture is designed.
The cutting force for this operation is calculated in paragraph 1.10, then I take all the data for the calculation from there.
To ensure the reliability of the clamping of the workpiece, it is necessary to determine the safety factor according to the formula:
where - guaranteed safety factor
Coefficient that takes into account the increase in cutting forces due to random irregularities on machined surfaces
Coefficient characterizing the increase in cutting forces due to blunting of the cutting tool
Coefficient that takes into account the increase in cutting forces during interrupted cutting
Coefficient characterizing the clamping forces in the clamping mechanism
Coefficient characterizing the economics of manual clamping mechanisms
Coefficient that takes into account the presence of moments tending to rotate the workpiece mounted on a flat surface
Since we accept
The required clamping force is determined by the formula:
The area of the pneumatic cylinder piston is determined by the formula:
where - network pressure \u003d 0.38 MPa
The diameter of the pneumatic cylinder is determined by the formula:
I accept the standard diameter of the pneumatic cylinder
I determine the actual clamping force of the cylinder
Determining the timing of the cylinder
where is the stroke of the rod
Rod speed, m/s
Calculation of the economic feasibility of the device
The calculation of the economic feasibility of using the designed device is based on a comparison of costs and economic feasibility.
where - annual savings, excluding annual costs for adaptation, rub.
P - annual cost of fixtures
Annual savings is determined by the formula
de-piece time when processing a part without fixture = 1.52 min
Unit time for the operation after the introduction of the device
Hourly rate for the operation of the workplace for the type of production
25 rubles/hour
N - annual release program
Annual costs are determined by the formula:
where is the cost of the device
A - depreciation factor
B-factor taking into account the repair and storage of fixtures
P \u003d 4500 (0.56 + 0.11) \u003d 3015 rubles.
According to production calculations and the expediency condition, in my case this condition is met.
From this I conclude that the use of the designed device is economically feasible.
2.2 Description of the design and calculation of the special cuttingtool
When designing a cutting tool, certain conditions must be met:
Find the best sharpening angles;
Determine the forces acting on the cutting parts;
Choose the most suitable material for the cutting part and the connecting part of the tool;
Set the allowable deviations in the dimensions of the working and connecting parts of the tool, depending on the working conditions and the required accuracy and quality of the surface being machined;
Make the necessary calculations of the elements of the cutting tool and, if necessary, make calculations for strength and rigidity;
Develop a working drawing of the tool with the necessary technical requirements for operation and its manufacture;
Calculate the economic costs of tool materials.
Based on the above conditions, I calculate a three-sided disk cutter for milling grooves in size 20h11 at operation 015 Milling
Initial data for calculation:
Workpiece material 30HGSA;
Machining allowance t=9 mm
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