The solution of practical problems in all main sections is given academic discipline"Technology of mechanical engineering". Variants of individual assignments for practical work are given with a description of the methodology for their implementation on the example of solving one of the assignment options. The annexes contain regulatory and reference materials necessary for the implementation practical work.
The textbook can be used in the study of the general professional discipline "Technology of mechanical engineering" in accordance with the Federal State Educational Standards of secondary vocational education for the specialty 151901 "Technology of mechanical engineering".
An electronic educational resource "Mechanical Engineering Technology" has been released for this textbook.
For students of secondary educational institutions vocational education.
DETERMINATION OF THE VALUE OF ALLOWANCES.
A blank is an object of production, the shape of which is close to the shape of a part, from which a part or a one-piece assembly unit is made by changing the shape and roughness of surfaces, their dimensions, as well as the properties of the material. It is generally accepted that a workpiece enters any operation, and a part leaves the operation.
The configuration of the workpiece is determined by the design of the part, its dimensions, material and working conditions of the part in finished product, i.e., all types of loads acting on the part during the operation of the finished product.
The initial workpiece is the workpiece that enters the first operation. technological process.
An allowance is a layer of workpiece material that is removed during its machining to obtain the required accuracy and parameters of the surface layer of the finished part.
An intermediate allowance is a layer of material removed during one technological transition. It is defined as the difference between the size of the surface of the workpiece, obtained in the previous operation, and the size of the same surface of the part, obtained by performing this transition for processing the surface of the workpiece in one operation.
TABLE OF CONTENTS
Foreword
Chapter 1. Fundamentals of mechanical engineering technology
1.1. Production and technological processes of a machine-building enterprise
Practical work No. 1.1. Studying the structure of the technological process
1.2. Determining the amount of allowances
1.3. Calculation of workpiece dimensions
1.4. Preliminary assessment of options for obtaining blanks
and their manufacturability
Practical work №1.2. Appointment of operating rooms
allowances for processing a part with a graphic representation of the location of allowances and tolerances for operating dimensions
1.5. Selection of bases when processing workpieces
1.6. Sequence of operations
1.7. Selecting an installation base
1.8. Selection of the initial base
Practical work No. 1.3. Allocation of workpieces in the processing area of the machine
1.9. Machining precision
1.10. Determining the expected accuracy when automatically obtaining the coordinating dimension
Chapter 2. Technical regulation of technological operations
2.1. Piece time structure
2.2. Rationing operations
Practical work №2.1. Rationing of the turning operation of the technological process
Practical work №2.2. Rationing of the milling operation of the technological process
Practical work №2.3. Rationing of the grinding operation of the technological process
2.3. Operations Development
Practical work №2.4. Development of a cylindrical grinding operation of the technological process
Practical work №2.5. Development of surface grinding operation of the technological process
Chapter 3. Surface treatment methods used in the manufacture of main parts
3.1. Shaft manufacturing
3.2. Disc manufacturing
3.3. Gear manufacturing
3.4. Production of spur gears
3.5. Manufacturing of bevel gears
Chapter 4
Chapter 5
Chapter 6
Chapter 7. Assembly of connections, mechanisms and assembly units
7.1. Development of the route and assembly scheme
7.2. Assembly dimensional chains
7.3. Ensuring Assembly Accuracy
7.4. Control of assembly and technological parameters
7.5. Balancing parts and rotors
Chapter 8
8.1. The main provisions of the course project
8.2. General requirements to the design of the course project
8.3. General methodology for working on a project
8.4. Technological part
Applications
Attachment 1. Approximate form title page explanatory note
Appendix 2. An approximate form of the assignment form for a course project
Appendix 3. Units of measurement of physical quantities
Annex 4. Rules for the design of the graphic part of the course project
Appendix 5. Tolerances in the hole system for external dimensions according to ESDP (GOST 25347-82)
Appendix 6. Approximate routes for obtaining parameters of external cylindrical surfaces
Appendix 7. Approximate routes for obtaining parameters of internal cylindrical surfaces
Annex 8. Operating allowances and tolerances
Annex 9. Time indicators of technological operations
Appendix 10 Specifications technological equipment and materials
Appendix 11. Cutting parameters and processing modes
Appendix 12. Indicators of accuracy and surface quality
Annex 13. Dependence of the type of production on the volume of output
Appendix 14. Approximate indicators for economic calculations
Appendix 15. Surface Treatment Methods
Annex 16. Values of coefficients and quantities
Annex 17. Brief specifications machine tools
Bibliography.
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1 FEDERAL EDUCATION AGENCY educational institution higher professional education "TOMSK POLYTECHNICAL UNIVERSITY" YURGA TECHNOLOGICAL INSTITUTE А.А. Saprykin, V.L. Bibik COLLECTION OF PRACTICAL TASKS ON THE DISCIPLINE "ENGINEERING TECHNOLOGY" Textbook Publishing house of Tomsk Polytechnic University 2008
2 LBC 34.5 i 73 UDC (076) C 19 C 19 Saprykin A.A. Collection of practical tasks in the discipline "Technology of mechanical engineering": tutorial/ A.A. Saprykin, V.L. Bibik. Tomsk: Publishing House of the Tomsk Polytechnic University, p. The manual contains examples and tasks with solutions. It will help to acquire skills in solving technological problems, determining the improvement of existing and developing new technological processes. Designed to perform practical work in the discipline "Technology of Mechanical Engineering" by students of universities specializing in "Technology of Mechanical Engineering". UDC (076) Reviewers Doctor of Technical Sciences, Professor of TPU S.I. Petrushin Deputy Head of Workshop 23, Yurginsky Machine Plant LLC P.N. Bespalov Yurga Technological Institute (branch) of Tomsk Polytechnic University, 2008 Design. Publishing house of Tomsk Polytechnic University,
3 CONTENTS CHAPTER 1. FUNDAMENTALS OF DESIGN OF TECHNOLOGICAL PROJECTS PRODUCTION AND TECHNOLOGICAL PROCESSES.4 2. PRECISION OF MECHANICAL PROCESSING OF THE BASE AND PRINCIPLES OF BASED MANUFACTURING OF THE DESIGN ALLOWANCES FOR MECHANICAL PROCESSING. OPERATING DIMENSIONS AND THEIR TOLERANCES PROCEDURE FOR DESIGNING TECHNOLOGICAL PROCESSES QUALITY CONTROL OF PRODUCTS METHODS OF INSTALLING WORKPIECES. INSTALLATION ELEMENTS OF DEVICES 57 CHAPTER 2. METHODS OF PROCESSING THE MAIN SURFACES OF WORKPIECES TREATMENT OF THE EXTERNAL SURFACES OF THE BODIES OF ROTATION...62 CHAPTER 3. TECHNOLOGY OF ASSEMBLY OF MACHINES DESIGN OF THE TECHNOLOGICAL PROCESS OF ASSEMBLY...75 APPENDIX A..83 LIST
4 CHAPTER 1. BASICS OF TECHNOLOGICAL PROCESS DESIGN 1. PRODUCTION AND TECHNOLOGICAL PROCESSES When designing a technological process and its implementation and when preparing technological documentation, it is important to be able to determine the structure of a technological process and correctly formulate the name and content of its elements. In this work, GOST and An important milestone in the development of the technological process is also the definition of the type of production. Approximately the type of production is set at the initial design stage. The main criterion in this case is the coefficient of consolidation of operations. This is the ratio of the number of all technological operations performed during certain period, for example, a month, in a mechanical section (O), and to the number of jobs (P) of this section: K z.o \u003d O / P. (1.1) Types of machine-building industries are characterized by the following values coefficient of consolidation of operations: K z.o<1 массовое производство; 1<К з.о 10 крупносерийное производство; 10<К з.о 20 среднесерийное производство; 20<К з.о 40 мелкосерийное производство; К з.о не регламентируется единичное производство. Формулирование наименования и содержания операции Пример 1.1. Деталь (втулку) изготовляют в условиях серийного производства и из горячекатаного проката, разрезанного на штучные заготовки. Все поверхности обрабатываются однократно. Токарная операция выполняется согласно двум операционным эскизам по установкам (рис.1.1). 4
Fig Operating sketches Required: to analyze operational sketches and other input data; establish the content of the operation and formulate its name and content; set the workpiece processing sequence in this operation; describe the content of the transition operation. Solution. 1. Analyzing the initial data, we establish that in the operation under consideration, which consists of two installations, nine surfaces of the workpiece are processed, which will require sequentially nine technological transitions. 2. To perform the operation, a lathe or screw-cutting lathe will be used, and the name of the operation will be “Turning” or “Screw-cutting lathe” (GOST). According to the same GOST, we determine the number of the operation group (14) and the operation number (63). To record the content of the operation in the presence of operational sketches, an abbreviated form of recording can be used: “Cut three ends”, “Drill and bore a hole”, “Bore one and grind two chamfers”. 3. We establish a rational sequence for performing technological transitions according to the installations, guided by operational sketches. In the first installation, it is necessary to cut 5
6 end 4, grind surface 2 to form end 1, chamfer 3, drill hole 6 and bore chamfer 5. In the second setting, cut end 9, grind surface 7 and chamfer 8. Set and clamp the workpiece 2 PT Cut the end 4 Turn surface 2 to form an end 1 3 PT (turning surface 2 takes 2 work steps) 4 PT Turn the chamfer 3 5 RT Drill a hole 6 6 RT Boring the chamfer 5 7 RC Reposition the workpiece 8 PT Undercut butt 9 9 PT Sharpen the surface 7 10 PT Sharpen the chamfer 8 11 PV Control of the dimensions of parts 12 PV Remove the part and put it in a container 4. The content of the operation in the technological documentation is recorded by transitions: technological (PT) and auxiliary (IL). When formulating the content of transitions, the abbreviated entry according to GOST is used. Table 1.1 shows the entries of the example under consideration. Task 1.1. For the turning operation, an operational sketch has been developed and the execution dimensions with tolerances and requirements for the roughness of the machined surfaces have been set (Fig. 1.2). Each surface is treated once. 6
7 3 I, V I R a Å Ç 2 5 H 1 2 I I, V I I 2 45 Å 3 2 à ñ ê and Ç 9 4, 5 h V I, I X R a 2 0 Ç 6 0 h 1 1 Ç 5 0 h 1 1 Ç 4 5 H 1 2 Ç 6 5 H 1 2 Ç H * 2 5 * * î î ê 4 5 ± 0, ± 0.3 3 V, X R a 1 0 Ç , 5 Ç 5 5 H 1 2 Ç h h ± 0.5 Figure Operating sketches 7
8 Required: set machine type; determine the configuration and dimensions of the workpiece; establish a basing scheme; number on the sketch all the surfaces to be machined; formulate the name and content of the operation for recording in technological documents; record the content of all technological transitions in the technological sequence in full and abbreviated forms. Establishing the name and structure of the operation and recording its content in the technological documentation Example 1.2. In Figure 1.3, which is a fragment of the working drawing of the part, a structural element of the part to be processed in mass production is highlighted. R a 20 Z 18 H 12 6 Z ± 0, 2 8 Z * * R e m a r d e r d y s r a w e Fig Working drawing Required: to analyze the initial data; choose the method of processing the constructive type of production; choose the type of metal-cutting machine; set the name of the operation; write down the contents of the operation in full; formulate a record of the content of the operation on technological transitions. Solution. 1. We establish that six holes in the housing flange are to be machined, evenly spaced on a circle Ø 280 mm. 2. Holes in solid material are made by drilling. 3. For processing, we select a radial drilling machine. 4. The name of the operation (according to the type of machine used) "Radial drilling". 5. Recording the contents of the operation in full form is as follows: “Drill 6 through holes Ø18H12 in series, maintaining
9 d = (280 ± 0.2) mm and surface roughness Ra = 20 µm, according to the drawing. 6. Recording the content of transitions in full form is as follows: 1st transition (auxiliary). Install the workpiece in the jig and secure. 2,..., 7th transitions (technological). Drill 6 holes Ø18H12, maintaining dimensions d = 280±0.2; Ra20 in series on the conductor. 8th transition (auxiliary). Size control. 9th transition (auxiliary). Remove the blank and place in a container. Task 1.2. Set the name and structure of the operation in the conditions of mass production for the processing of structural elements of the part (Fig. 1.4). Variant numbers are indicated in the figure in Roman numerals. I, I I I I I, I V 3 R a 5 R a Ç 3 4 h 1 0 M g V, V I 4 0 ± 1 V I I, V I I I Ç 6 0 H 1 2 R a 1 2.5 R a 5 Ç 6 0 H ± 0 , 3 I Õ, X 1 5 H 1 0 Fig Operational sketches 9
10 Establishing the type of production at the site Example 1.3. There are 18 jobs in the machine shop area. Within a month, 154 different technological operations are performed on them. Required: to establish the load factor of operations on the site; determine the type of production: state its definition in accordance with GOST Decision. 1. The coefficient of fixing operations is set according to the formula (1.1): K z.o = 154/18 = 8.56. In our case, this means that on the site, each workplace is assigned an average of 8.56 operations. 2. The type of production is determined according to GOST and Since 1<К з.о <10, тип производства крупносерийное. 3. Серийное производство характеризуется ограниченной номенклатурой изделий, сравнительно большим объемом их выпуска; изготовление ведется периодически повторяющимися партиями. Крупносерийное производство является одной из разновидностей серийного производства и по своим техническим, организационным и экономическим показателям близко к массовому производству. Задача 1.3. Известно количество рабочих мест участка (Р) и количество технологических операций, выполняемых на них в течение месяца (О). Варианты приведены в табл Требуется: определить тип производства. Таблица 1.2 Данные для расчета коэффициента закрепления операций варианта I II III IV V VI VII VIII IX X Количество рабочих мест (Р) Количество технологических операций (О)
11 2. PRECISION OF MECHANICAL PROCESSING One of the main tasks of technologists and other participants in production in machine shops is to ensure the required accuracy of manufactured parts. Real machine parts made by machining have parameters that differ from ideal values, that is, they have errors, the size of the errors should not exceed the permissible maximum deviations (tolerances). To ensure the specified accuracy of processing, the technological process must be correctly designed, taking into account the economic accuracy achieved by various processing methods. The norms of average economic accuracy are given in the sources. It is important to consider that each next transition should increase the accuracy by quality. In some cases, calculation methods are used to determine the possible value of the processing error. This is how turning errors are determined, from the action of cutting forces arising from insufficient rigidity of the technological system. In a number of cases, the analysis of the accuracy of processing a batch of parts is carried out using the methods of mathematical statistics. Determination of economic accuracy achieved with various methods of processing external surfaces of revolution Example 2.1. The surface of the step of a steel shaft 480 mm long, made from a forging, is pre-treated on a lathe to a diameter of 91.2 mm (Fig. 2.1). R a 2 0 Ç 9 1, 2 Figure Stepped shaft Determine: economic accuracy of machining size 91.2; quality of accuracy of the processed surface and its roughness. eleven
12 Decision. To determine the economic accuracy, use the tables "Economic accuracy of machining", which are given in various reference books. In our case, after rough turning, the accuracy of the machined surface should be within the th grade (we accept the 13th grade). Considering that at l/d = 5.3, the processing errors increase by 1.5...1.6 times, this corresponds to a decrease in accuracy by one grade. We finally accept the accuracy of the 14th grade. Since the size of the workpiece is intermediate during rough turning, this size is set for the outer surface with a tolerance field of the main part Ø91.2h14, or Ø91.2-0.37. Surface roughness Ra = µm (in the practice of factories with well-made workpieces and normal production conditions, a higher machining accuracy is achieved). Task 2.1. One of the shaft steps is machined by one of the indicated methods. The numbers of options are given in the table. Required: to establish the economic accuracy of processing; perform an operational sketch and indicate on it the size, quality of accuracy, tolerance size and roughness. Assume that the surface of the considered shaft step has a tolerance field of the main part (h). variant Initial data Table 2.1 Processing method and its nature Shaft length, mm I Lapping II Semi-finishing turning III Fine grinding IV Single turning V Superfinishing Step diameter, mm VI Preliminary grinding VII Fine turning VIII Final turning IX Diamond burnishing X Final grinding
13 Determining the accuracy of the shape of the surfaces of the part during processing Example 2.2. On the outer surface of the shaft (Fig. 2.2), a shape tolerance is specified, indicated by a symbol according to STSEV. The final processing of this surface is supposed to be performed by grinding on a cylindrical grinding machine model ZM151. Required: to establish the name and content of the symbol of the specified deviation; establish the ability to withstand the requirement for the accuracy of the shape of this surface during the intended processing. 0.01 З 7 0 Fig Shaft sketch Solution. 1. According to the presented sketch, the accuracy of the shape of the cylindrical surface is expressed by the roundness tolerance and is 10 microns. According to GOST, this tolerance corresponds to the 6th degree of form accuracy. The term "Tolerance of steepness" means the largest allowable deviation from roundness. Particular types of deviation from roundness are ovality, faceting, etc. 2. On a circular grinding machine model ZM151, it is possible to process workpieces with a maximum diameter of up to 200 mm and a length of up to 700 mm. Therefore, it is suitable for processing this workpiece. The deviation from roundness during processing on this machine is 2.5 microns. Based on the foregoing, we conclude that it is possible to perform processing with a given accuracy. Task 2.2. On fig. 2.3 and in table. 2.2 shows surface options with permissible shape deviations. Required: to establish the name and content of the designation of the indicated deviations; set the ability to perform processing on the specified machine, observing the specified accuracy. Specify the missing dimensions. 13
14 I 0, V, V I Ç , 0 5 Ç 5 0 I I, I I I 0. 02 À 0. 02 V I I 0, À I V 0. 0 2 V I I I 0. 1 5 I X, X 0, Fig Operational sketches 14
15 Initial data Table 2.2 options Surface shape Type of machine I Hole Internal grinding II Plane Surface grinding III Plane Surface grinding IV Edge Cylindrical grinding V, VI Hole Honing VII Cylinder Screw-cutting lathe VIII Plane Longitudinal planing IX Cylinder Turning multi-cutting Cylinder X Cylindrical grinding Determining the accuracy of the relative position of the workpiece surfaces during processing Example 2.3. The sketch (Fig. 2.4) indicates the technical requirement for the accuracy of the relative position of the surfaces of the part. The final processing of the upper plane is supposed to be performed by finishing milling on a vertical milling machine according to the operational sketch shown in Fig. 2 / õ À 0, 2 / õ À À Fig Design requirements À Fig Operational sketch establish the accuracy of the relative position of the surfaces of the part according to the technological reference books, depending on the type of equipment; conclude that it is possible to meet the specified requirement. Solution. 1. The symbol on the working drawing shows the parallelism tolerance of the upper plane relative to the lower plane, indicated by the letter A. The parallelism tolerance is understood as the largest allowable deviation from 15
16 parallelism. In our case, the tolerance is 0.2 mm over an area of mm. 2. In the tables of technological reference books, for example, we find the maximum deviations of our case: they are equal to microns and microns at a length of 300 mm, which means that at a length of 150 mm they will be equal to 12 microns. Of all these data, we accept for guarantee the largest value of 100 microns, i.e. 0.1 mm. 3. We conclude that the required accuracy of the relative position of the machined plane relative to the base plane A will be ensured. Task 2.3. On fig. 2.6 shows surface treatment options. Required: to decipher the designation of the content of the tolerance; develop technological measures to ensure the fulfillment of this requirement. À I, I I 0, À À I I I, I V 0, À V, V I V I I, V I I I 0, 1 5 À Á 0, 0 4 À Á I X, X 0, 0 5 À À Figure Surface treatment options 16
17 3. BASES AND PRINCIPLES OF LOCATION In order to process a workpiece on the machine, it must be fixed on it, having previously selected the bases. By basing is meant giving the workpiece the required position relative to the machine and tool. The accuracy of processing depends on the correctness of the basing. When developing a basing scheme, the issues of choosing and placing reference points are solved. Under production conditions, processing errors ε set always occur, depending on the installation conditions, i.e. from basing ε bases, fastening ε closing the workpiece, and from the inaccuracy of the fixture ε etc. The installation error is expressed by the formula: ε = ε + ε + ε. (3.1) set of bases To reduce these errors, it is important to follow the rules of basing: the rule of "six points", the rule of "constancy of bases", the rule of "combination of bases", etc. Error values can be determined by various methods. The tabular method allows you to determine the installation errors depending on the production conditions. The calculation method for determining the errors of basing, fixing and caused by the inaccuracy of the fixture is performed using the formulas given in the literature. If the rule of "combining the bases" is not observed, it becomes necessary to recalculate the design dimensions into technological ones (Fig. 3.1). The purpose of the recalculation is to determine the error in the size of the master link and compare it with the tolerance of the design size. Á Ê close pr H = 7 5 h 9 h = 3 0 H * À 1 Ò = À 2 À S Á Ò Fig. Technological dimension chain 17
18 The calculation of dimensional chains is carried out in accordance with GOST and one of the methods indicated in them (“maximum minimum”, probabilistic, etc.). In these calculations, the formulas for determining the nominal size of the closing link are used: h = H T, (3.2) where H is the size that connects the design and technological bases; T is the size that connects the technological base with the surface to be treated. The error in the size of the closing link ε h =ε Δ when solving by the method of "maximum minimum" is determined by the formulas: ε = T + T ; ε = T =, (3.3) h H T n h Σ T i 1 where Ti is the tolerance for the size of each chain link; T N tolerance for size H established by the drawing; T T tolerance for the technological size, the value of which depends on the method of processing and is set in accordance with the standard of average economic accuracy of processing; n is the number of constituent links. When calculating according to the probabilistic method, the following formulas are used: Т n 2 = t λiti, (3.4) i= 1 where t is the risk coefficient (t = 3); λi is the relative scattering coefficient (for the normal distribution law λi = 1/9). When the distribution laws are unknown, they take t = 3 and λi = 1/6, hence n T i i= 1 2 T 1.2t. (3.5) = As a result of the calculation, the condition T h T Σ must be met. (3.6) 18
19 à Choice of technological base taking into account the technical requirements for the part Example 3.1. In the technological process of manufacturing the case, an operation is provided for boring a hole with a diameter D (Fig. 3.2). When making a hole, dimension a and technical requirements regarding the correct relative position of the hole relative to other surfaces of the part must be observed. Â H 0.1 À 6 Ã Á 6 Â D 4 5 4.5 Á 0.1 Â 22 0.1 Á Fig Working drawing À À , Fig.3.3. Basing scheme Required: select a technological base for the operation in question; develop a base plan. Solution. 1. One of the design bases is the plane A of the base. It should be taken as a technological installation base, creating three reference points 1, 2 and 3 for its basing (Fig. 3.3). The technological guide base should be plane B with two reference points 4 and 5. This base will allow you to process a hole perpendicular to this plane. To ensure the symmetry of the location of the hole relative to the outer contour, surface C can be used as a technological base, but it is structurally easier to use the surface G of the half-cylinder for this and use a device with a movable prism for this purpose. Based on the foregoing, we apply the technological base of three surfaces: A, B and D (Fig. 3.3). 2. The basing scheme, which is the location of reference points on the bases of the workpiece, is shown in Fig.
20 a Problem 3.1. For a machine operation for processing the specified surface of a part, it is required to select a technological base and draw up a basing scheme. Options are shown in fig. 3.4 and in Table d , 1  0, 1 À 0, 1 Á Fig Operational sketches  option I Name and content of operations Name of operation Operation content Cylindrical grinding finish VI, VII Horizontal milling Mill a groove VIII Vertical milling Mill a groove IX Vertical drilling Drill 2 holes X Fine boring Boring 2 holes 20
21 Determination of the technological base and drawing up a scheme for basing the workpiece Example 3.2. Required: consider the installation elements of the existing fixture (Fig. 3.5) and install the workpiece surfaces that make up the technological base when fixing the workpiece in the fixture; develop a scheme for basing the workpiece and draw a conclusion about compliance with the six-point rule. Solution. 1. In the device shown in the figure, we identify its installation elements: the plane of the body 2, the installation cylindrical pin and the installation sheared finger 3. The technological base of the workpiece is the following surfaces: the lower plane of the workpiece A and two holes located diagonally. 2. In accordance with the identified technological bases and the used installation elements, we develop a basing scheme (Fig. 3.6): three reference points (1, 2, 3) are formed to locate the plane (installation base); for basing on the first hole (using a cylindrical pin), two more reference points (4, 5) are formed, and for basing on the second hole, a cut pin (6) is used, forming the 6th basing point. 3. As can be seen from Figure 3.6 and the above reasoning, the six-point basing rule is observed, the workpiece is deprived of six degrees of freedom А Fig. Workpiece basing 21
22 Fig. Basing scheme 6 Task 3.2. On fig. 3.7 shows a fixture for processing on a machine. It is necessary, using the figure, to identify the technological base adopted for basing the workpiece, and present the scheme for basing the workpiece; make a conclusion about the correctness of the choice of reference points by the number and placement of them. The variant number is indicated in the figure by a Roman numeral. I, I I A - A I I I, I V, V À À V I, V I I V I I I, I X, X Fig Tools 22
23 Calculation of a linear technological dimensional chain Example 3.3. On the adjusted horizontal milling machine, working on setup, the specified plane is finished. In this case, the coordinating size h \u003d (70 ± 0.05) mm must be maintained (Fig. 3.8). Size tolerance h = 0.1 mm. Required: to determine whether the specified size accuracy will be maintained during processing. B - c o n s t r u c t o r s y a y b z z À h 8 (- 0,) À Σ = h = 7 0 ± 0, 0 5 À 1 = 8 5 h 8 (- 0,) A - t e x n l l o g e s y a b z o Fig Technological dimensional chain Solution. 1. From the condition of the example and from the operational sketch, it can be seen that the lower plane A of the workpiece is taken as the technological base. The design and measurement bases for controlling the size h is the upper plane B. Due to the fact that the bases do not match, it became necessary to recalculate the design dimensions for technological ones. In this case, it is necessary to calculate the error with which the size h can be made, and compare it with the tolerance T h of this size, the condition ε h T h must be met. 2. The dimensional chain under consideration is linear and consists of three links: the size h = 70 mm of interest to us will be considered the closing link A, the first component link, the size A 1 = 85h8 (85-0.04) between the previously processed planes is an increasing link; the second component link size A 2 is technological, reducing, and its accuracy is determined by the norms of economic accuracy of processing on machine tools (see GOST). For our case, the error of this size is 0.06 mm. The nominal dimensions of this chain are related by Equation 23
24 A = A 1 A 2 = = 70 mm. 3. When calculating a linear dimensional chain (Fig. 3.8) by the method of complete interchangeability, i.e. using the maximum minimum method, determine the maximum deviations (processing error) of the initial (closing) link according to the formula (3.3): T n = Ti = (TA 1 + TA2) = (0.06) = 0.114mm Σ. i= 1 As follows from the solution, the drawing tolerance T h = 0.1 mm is less than the possible processing error T = ε h = 0.114 mm, which is completely unacceptable. Therefore, it is necessary to take measures to achieve the fulfillment of the condition ε h T h. about expanding the tolerance T h to the value 0.12, then T = ε h = (0.06) T h. Secondly, apply fine milling or fine grinding as a final (finishing) treatment. The economic accuracy of these processes is higher and with them T A2 =0.025 mm (GOST). Then T = (0.025) = 0.079 mm. The condition T T h is met. Thirdly, the component size A = 85h8 was obtained during the processing of planes A and B before the operation in question. If the previous processing is performed more accurately by one quality, then the size tolerance will be 85h7 (-0.035). Then the processing error T = (0.035 +0.06) = 0.095 mm. The condition is met T T h. Fourth, when calculating the dimensional chain, you can use the probabilistic method according to the formula n T i i = 1 2 T 1.2t. 2 2 Then T = 1.2 0.060 = 0.097 mm and the condition T Th is met. Fifthly, the tolerance of the closing link is calculated using the theory of probability for the case of dispersion of deviation errors according to the law of normal distribution according to the formula (3.5). In our case, 2 2 TΣ = 0.060 = 0.08mm. The condition T T h is fulfilled. Sixth, with a small volume of production of parts, i.e., in a single or small-scale production, it is possible to work not on adjustment, but, for example, with the removal of test chips. When processing each part, the size h is controlled. = 24
25 Task 3.3. On fig. 3.9 and in table. 3.2 presents options for operations. Required: to determine the possible error of size basing as a result of the specified processing. I, I I I I I, I V 1 2 l V, V I l 2 l 1 l h 9 Ç Ç Ç l 1 l 2 V I I, V I I I h 9 1 l 2 l 1 2 Ç Ç Ç h h h 1 0 l 1 I X, X 1 2 l 2 Fig Options for calculating dimensional chains Initial data Table 3.2 of the option Content of the operation Size l, mm I Plane plane 1 in advance l 1 = 150 + 0.2 II Plane plane 2 finally l 2 = 170 ± 0.1 III Cut end 1 in advance l 1 =60+0.3 IV Cut end 2 finally l 2 =30+0.1 V Cut end 1 first L 1 = 100+0.2 VI Cut end 2 finally l 2 =50+0.1 25
26 Continuation of table 3.2 VII Grind plane 1 preliminary l 1 =75+0.1 VIII Grind plane 2 finally l 2 = 175+0.2 IX Mill plane 1 preliminary l 1 =70+0.4 X Mill plane 2 finally l 2 =30+0.2 4. MANUFACTURING DESIGN Successful solution of the tasks that are and will continue to face mechanical engineering is possible only when creating new and improving existing machines in order to achieve higher performance while reducing their weight, dimensions and cost, increase durability, ease of maintenance and reliability in operation. At the same time, in machine building itself, it is necessary to improve the technological processes of manufacturing products, improve the use of all means of technological equipment, and introduce progressive methods of organizing production into production. One of the effective ways to solve these problems is the introduction of the principles of manufacturability of structures. This term is understood as such a design that, subject to all operational qualities, ensures minimal labor intensity of manufacturing, material consumption and cost, as well as the possibility of quickly mastering the production of products in a given volume using modern processing and assembly methods. Manufacturability is the most important technical basis that ensures the use of design and technological reserves to fulfill the tasks of improving the technical and economic indicators of manufacturing and product quality. Work to improve manufacturability should be carried out at all stages of design and development in the production of manufactured products. When performing work related to manufacturability, one should be guided by a group of standards included in the Unified System for Technological Preparation of Production (USTPP), namely GOST, as well as GOST "Technological control in design documentation". The manufacturability of the design of parts is determined by: a) a rational choice of initial blanks and materials; b) manufacturability of the shape of the part; c) rational arrangement 26
27 sizes; d) the appointment of the optimal accuracy of dimensions, shape and relative position of surfaces, roughness parameters and technical requirements. The manufacturability of the part depends on the type of production; selected technological process, equipment and tooling; the organization of production, as well as the operating conditions of the part and assembly unit in the product and the conditions of repair. Signs of the manufacturability of the design of the part, for example, a subclass of shafts, are the presence of small differences in the diameters of the steps for stepped shafts, the location of stepped surfaces with a decrease in diameter from the middle or from one of the ends, the availability of all machined surfaces for machining, the ability to use the original workpiece of a progressive type for the manufacture of the part , which is close in shape and dimensions to the shape and dimensions of the finished part, the ability to apply high-performance methods for processing. Improving the manufacturability of the original workpiece Example 4.1. Two options for the design of the original workpiece, obtained by casting, were made for the manufacture of the support body (Fig. 4.1, a, b). It is required to establish which of the options has a more technologically advanced design of the original workpiece. Solution. The housing (Fig. 4.1, a) has a tubular cavity in the lower part. To form it in the mold, it will be necessary to use a cantilever rod, and this will complicate and increase the cost of manufacturing the casting. A smooth hole of considerable length in the upper part will complicate machining. The body (Fig. 4.1, b) has a cruciform section in the lower part, which has high strength and rigidity, and a rod is not needed to make a casting. This greatly facilitates the production of molds for casting. The casting is symmetrical with respect to the vertical plane and will easily be molded in two flasks. The hole in the middle part has a recess and therefore the length of the surface of the hole to be machined is reduced, and this, in turn, greatly facilitates and reduces the cost of machining. Based on the above considerations, it can be concluded that the second option is more technologically advanced. 27
28 À À À - À à) b) Fig Variants of casting shape Problem 4.1. When designing the original workpiece or its elements, two designs were proposed (options are given in Table 4.1, in Fig. 4.2). Table 4.1 Initial data of the option Part name Type of workpiece I; VIII; VIIIII; VIIIIV; IXV; X Toothed wheel Lever Cover Body mouth Round body Stamped forging The same Casting Welded Casting I, V I I I, V I I I I I, V I I I I V, I X V, X Figure Options for blanks 28
29 It is required to state considerations for assessing the manufacturability of the design of each of the options for the initial workpiece and to establish a more manufacturable one. Improving the manufacturability of parts and their elements Example 4.2. In order to improve the technical and economic indicators of the technological process, two options for performing the part of the elements in the structure of the body, made from castings, are proposed (Fig. 4.3, a, b). It is required to evaluate their manufacturability. Solution. Bosses and plates on the body of the part (Fig. 4.3, a) are located at different levels, and each boss has to be processed according to individual adjustment. Insufficient rigidity of the upper part of the part does not allow the use of high-performance machining methods. In the design in Fig. 4.3, b, all machined surfaces are located in the same plane and therefore can be machined on one machine, for example, on a vertical milling or longitudinal milling machine. a) b) Fig Casting options Added ribs on the inside of the part increase the rigidity of the body. During processing, this will help reduce the deformation of the workpiece from cutting and clamping forces and will allow processing with high cutting conditions or several tools at the same time. This will improve the accuracy and quality of the machined surfaces. 29
30 The level of the unmachined surfaces of the part is below the machined surfaces. This will allow for more efficient processing "per pass". Task 4.2. One and the same structural element of a machine part can be structurally solved differently. These solutions are represented by two sketches (options in Fig. 4.4). It is required to analyze the compared sketches of structures for manufacturability and justify the choice of a structural element of the part. I, I I V I I, V I I I I I I, I V V, V I I X, X R Body weighing m D = 2 kg is made of cast iron SCh 20 GOST. workpiece mass m 0 \u003d 2.62 kg. thirty
31 The complexity of the machining of the part T i = 45 min with the basic labor input (analogue) = 58 min. Technological cost of the part С m = 2.1 rubles. at the basic technological cost of analogue C b.t. = 2.45 rubles. The data of the design analysis of the part on the surfaces are presented in Table 4.2 Initial data Name of the surface Number of surfaces Number of unified elements Main hole 1 1 Flange end 2 Chamfer 2 2 Threaded hole 8 8 Top of the base 2 Holes of the base 4 4 Bottom of the base 1 Total ... Q e =20 Q c.e. = 15 It is required to determine the manufacturability indicators of the part design. Solution. 1. The main indicators of the manufacturability of the design include: the absolute technical and economic indicator of the labor intensity of manufacturing the part T and = 45 min; the level of manufacturability of the design in terms of the complexity of manufacturing K U.T = T and /T b.i = 45/58 = 0.775. The part according to this indicator is technologically advanced, since its labor intensity is lower by 22.5% compared to the basic analogue; technological cost of the part C m = 2.1 rubles; the level of manufacturability of the design at the technological cost K y. c \u003d C t / C b.t \u003d 2.1 / 2.45 \u003d 0.857. The part is manufacturable, since its cost compared to the base analogue decreased by 14.3%. 2. Additional indicators: the coefficient of unification of the structural elements of the part K y. e \u003d Q y.e / Q e \u003d 15/20 \u003d 0.75. 31
32 According to this indicator, the part is technologically advanced, since K y. e>0.6 weight of the part m D = 2 kg; material utilization factor K and.m \u003d m d / m 0 \u003d 2 / 2.62 \u003d 0.76. For an initial blank of this type, this indicator indicates a satisfactory use of the material. Task 4.3. About the part in question, its original workpiece and its basic analogue or prototype are known; basic data given in table. 4.3 for ten options. It is required to determine the indicators of manufacturability of the design of the part. Table 4.3 Initial data of the option Number of surfaces of the part Qe Number of unified elements Qw.e Weight, kg Parts md of the Initial workpiece m0 Labor intensity, min Parts Ti Basic analogue Tb.i Cost price, rub. Details St Basic analogue C6.g I; VI .8 1.7 2.1 II; VII .3 0.9 1.3 III; VIII,1 3.4 4.1 IV; IX.2 0.2 1.4V; X ,8 5.8 5.3 5. MECHANICAL ALLOWANCES. OPERATING DIMENSIONS AND THEIR TOLERANCES When considering the elementary surface of the original workpiece and the corresponding surface of the finished part, the total allowance for machining is determined by comparing their sizes: this is the difference in the sizes of the corresponding surface on the original workpiece and the finished part. When considering the outer surface of rotation (on the left in Fig. 5.1), the total allowance: 2P total d \u003d d 0 d D; (5.1) 32
33 at the inner surface of rotation (in the center in Fig. 5.1) the total allowance: 2P total d \u003d D D D 0; (5.2) at a flat surface (on the right in Fig. 5.1) the total allowance for the side: P total h \u003d h 0 h D, (5.3) where d 0, D 0, h 0 are the dimensions of the original workpiece; d D, D D, h D corresponding dimensions of the finished part; 2P general d and 2P general d general allowances for diameter, outer surface and hole; П total allowance per side (end, plane). The machining allowance is usually removed sequentially in several transitions, and therefore for surfaces of revolution and for flat surfaces 2P total d = 2P i ; 2P total d = 2P i ; P total h = 2P i, (5.4) where Pi are intermediate allowances performed during the i-th transition, and at each next transition the size of the intermediate allowance is less than the previous one, and with each subsequent transition, the accuracy increases and the roughness of the machined surface decreases. Ï Ï d ä d 0 D ä D 0 h ä h 0 Ï Ï Ï Figure part processing technologies parameters intermediate dimensions of the workpiece, which appear in the technological documentation, depending on 33
34 from which performers select cutting and measuring tools. Intermediate allowances for each transition can be established by two methods: by the experimental-statistical method, using tables in GOSTs, in technological reference books, departmental guidance technological materials and other sources. These sources often lack tables to determine the operating allowances for the first rough transition. The operating allowance for the rough transition is determined by calculation according to the formula P 1 = P total (P 2 + Pz P n), (5.5) where P total is the total allowance for machining, established during the design of the workpiece; P 1, P 2; ..., P p intermediate allowances, respectively, for the 1st, 2nd, ..., nth transitions; calculation and analytical method according to special formulas, taking into account many processing factors. When calculating by this method, the operating allowances are less than those selected from the tables, which allows you to save metal, reduce the cost of processing. This method is used in the design of technological processes for processing parts with a large annual output. In the technological documentation and in the practice of processing, intermediate nominal sizes are used with permissible deviations. As can be seen in the diagram (Fig. 5.2) of the location of allowances and tolerances during processing, the nominal intermediate dimensions depend on the nominal allowances, which are found by the formula P nomi = P min i + T i-1, (5.6) where T i-1 is the tolerance on intermediate size at the previous transition. For various surfaces, the following formulas are used: for surfaces of revolution, except for the case of processing in centers: 2П nomi = 2(R zi-1 + h i Δ i 1 + ε) + T i-1 ; (5.7) 2 i for surfaces of revolution when machining in centers: 34
35 for flat surfaces 2П nomi = 2(R zi-1 +h i-1 +Δ Σi-1) + T i-1; (5.8) П nomi = 2(R zi-1 + h i-1 + Δ Σi-1 +ε i) + T i-1 ; (5.9) for two opposite flat surfaces with their simultaneous processing: П nomi = 2(R zi-1 + h i-1 + Δ Σi-1 +ε i) + T i-1, (5.10) where R Zi-1 the height of microroughnesses on the surface after the previous transition; h i-1 thickness (depth) of the defective layer obtained at the previous adjacent transition, for example, casting skin, decarburized or work-hardened layer (this term is not taken into account for cast iron parts, starting from the second transition, and for parts after heat treatment); Δ Σi-1 is the total value of spatial deviations of interconnected surfaces from the correct shape (warping, eccentricity, etc.), remaining after the previous transition (the total value of spatial deviations decreases with each next transition: Δ Σi = 0.06 Δ Σ0 ; Δ Σ2 = 0.05 Δ Σ1 , Δ Σ3 = 0.04 Δ Σ 2. When the workpiece or tool is not rigidly clamped, for example, in oscillating or floating holders Δ Σi-1 = 0); ε i is the error of setting the workpiece on the machine when performing the considered transition: 2 base 2 close 35 2 attachment ε = ε + ε + ε, (5.11) centers ε i = 0, when processing on multi-position operations when changing positions, the indexing error ε ind = 50 μm is taken into account by the formula ε i = 0.06 ε i-1 + ε ind); T i-1 tolerance for an intermediate size (when determining the allowance for the first rough transition for external surfaces, only its minus part T is taken into account, and for internal 0 surfaces, the plus part of the tolerance of the original workpiece). Intermediate dimensions when machining outer surfaces of revolution (shafts) are set in reverse order
36 of the technological process for processing this surface, i.e. from the size of the finished part to the size of the workpiece by successively adding to the largest limiting size of the finished surface of the part (initial calculated size) allowances P nom4; P nom3; P nom2; P nom1. The tolerances of these dimensions are set according to the shaft system with a tolerance field h of the corresponding quality. The maximum size limit of the finished surface is taken as the initial design size. Rounding of intermediate sizes is carried out in the direction of increasing the intermediate allowance to the same sign as the tolerance of this size. Features of calculating intermediate allowances and dimensions for internal surfaces are as follows: a) tolerances for intermediate (interoperational) dimensions are established according to the hole system with a tolerance field H of the corresponding qualification; b) the nominal dimensions and nominal allowances, at all transitions, except for the first, are related by the dependence П nomi = П mini +T i-1, (5.12) and the nominal allowance for the first (rough) transition is determined by the formula where П nomi = П mini + T 0 +, (5.13) + T 0 plus part of the workpiece tolerance; c) intermediate dimensions are set in the reverse order of the technological process from the size of the finished hole to the size of the workpiece by subtracting allowances P nom3 from the smallest limit size of the finished hole (initial size); P nom2; P nom1. Their tolerances are set according to the hole system with a tolerance field H; d) the smallest limit size of the finished hole is taken as the initial calculated size. The scheme of the tolerance fields of the outer surface of the part, workpieces at all stages of processing and the original workpiece and the fields of allowances of general and intermediate are shown in Fig.
37 + T 0 - d 0 n o m = d 1 n o m + 2 П 1 n o m 2 П 1 n o m T 1 d 1 n o m = d 2 n o m + 2 П 2 n o m 2 P 2 n o m - o l e d e r e n 2 d o m = d 3 n o m + 2 П 3 n o m 2 П 3 n o m T 3 d 3 n o m = d 4 n o m + 2 П 4 n o m 2 П 4 n o m T 4 I Preliminary I I Preliminary I I I Preliminary I V Scheme of tolerance fields First of all Choice of intermediate allowances when processing a rolled shaft and calculation of intermediate dimensions Example 5.1. A stepped shaft with a length L D \u003d 480 mm (Fig. 5.3) is manufactured in small-scale production from steel round hot-rolled steel of ordinary accuracy with a diameter of d 0 \u003d 100 mm. The shaft step with the largest diameter Ø90h10(90-0.35) with surface roughness Ra5 (Rz20) is processed twice: by preliminary and final turning. Required: set the total allowance for machining of the diametrical size; set intermediate allowances for both processing transitions by a statistical method; calculate intermediate size. R a 5 Z 9 0 h * Fig. Stepped shaft 37
38 Decision. 1. The total allowance for machining on the diameter is determined by the formula 5.1: 2P total d = = 10 mm. 2. Intermediate diameter allowance for fine turning of the shaft. 2P 2table = 1.2 mm. For small-scale production, the allowance increases, for which the coefficient K \u003d 1.3 is introduced, i.e. 2P 2calc \u003d 1.2 1.3 \u003d 1.56 mm 1.6 mm. Since there are no instructions regarding the size of the operating allowance for the diameter during rough turning in technological reference books, we determine it by calculation using the formula (5.4): So, the initial calculated size of the diameter (the largest limit size) is d and cx = 90 mm, the operating allowance for finishing turning 2P 2 = 1.6 mm. The diameter of the workpiece after rough turning is d 1 = d ref + 2P 2 = 91.6; it is also with a tolerance: d 1 \u003d 91.6h12, or d 1 \u003d 91.6-0.35; surface roughness Ra20. In the technological documentation, operational sketches are made for both transitions (Fig. 5.4, a, b) R a 20 Ç 9 1, 6 h 1 2 à) R a 5 Ç 9 0 h 1 0 b) Fig Operational sketches Task 5.1. For the manufacture of a stepped shaft (Fig. 5.5), steel round hot-rolled steel of ordinary accuracy with a diameter of d 0 was used as a workpiece. The largest diameter step of this shaft with a diameter of d D, manufactured with an accuracy of 11 grade and a surface roughness of Ra10, is processed 38
39 twice preliminary and final turning. The options for the task are given in Table d 0 d ä L ä Fig Blank circle Initial data Table 5.1 option I II III IV V VI VII VIII IX X d D mm using tables, total and intermediate allowances; calculate an intermediate size and perform operational sketches. Establishment by a statistical method (according to tables) of intermediate allowances for each transition and calculation of intermediate dimensions of the workpiece Example 5.2. The multi-stage shaft (Fig. 5.6) is made from stamped forgings of increased accuracy (Class I). The workpiece underwent milling and centering, as a result of which the ends were trimmed and center holes were created. 39
40 Ç 8 5 p 6 Ç 9 1, 2 + 0, 3-0, * Fig Forging blank The outer cylindrical surface of one shaft step has a diameter d = 85p6(85) * roughness Ra1.25. Step D of the original workpiece (see example P1.2) has a diameter d 0 = 91, and a roughness Rz250 (Ra60). The accepted sequence of processing of the indicated surface is given in the table Required: to analyze the initial data; establish by a statistical method (according to tables) operating allowances for each transition; calculate intermediate dimensions for each technological transition. Solution. 1. The total machining allowance per diameter is 6.2mm. The coefficient of hardening of the size of the machined surface is K stiff.r. = T 0 /T D = 2000/22 = 91. Table 5.2 Initial data Processing sequence (transition content) Sharpen the surface beforehand Sharpen the surface for grinding Grind the surface beforehand Grind the surface finally Grade of accuracy Roughness parameter Ra, µm 20.0 5.0 2 .5 1.25 Note that the permissible deviation of the diameter of the original workpiece corresponds to approximately the 16th grade of accuracy (IT16), and the finished part to the 6th grade of accuracy (IT6). Thus, the processing accuracy increases by about ten qualifications. Such a difference in accuracy can be achieved in four processing steps, so 40
41 how each stage of processing increases the accuracy of the size by an average of quality. 2. The choice of operating allowances for the diameter is performed according to the tables. Total allowance 2P total = 6.2 mm. The tabular value of the operating allowance for the diameter during grinding is 0.5 mm, we distribute it for preliminary and final grinding (approximately in a ratio of 3: 1) and get 2P 3 = 0.375 mm and 2P 4 = 0.125 mm. Rounded accept 2P 3 = 0.4; 2P 4 \u003d 0.1. Turning allowance for grinding 2P 2 \u003d 1.2 mm. From here we find the allowance for rough turning: 2P 1 = 2P total 2P 2 2P 3 2P 4 = 4.5 mm. The surface parameters after machining for each transition are presented in Table. 5.3, the following conclusions can be drawn: a) the total allowance is divided by transitions in relation to 72.5%, 19.5%, 6.5% and 1.5%, which corresponds to the rules of machining technology; b) after each transition, the accuracy increases in the following sequence (by qualifications): and, accordingly, the size tolerance decreases (the tolerance tightens) by 4.3; 3.8; 2.6 and 2.1 times; Table 5.3 Initial transition data Designation and size of the intermediate diameter allowance 0 2P total = 6.2 mm Tolerance field IT 16 (Class I according to GOST) 1 2P 1 =4.5 mm h13 2 2P 2 = 1.2 mm h10 3 2P 3 = 0.4 mm h8 4 2P 4 = 0.1 mm р6 41 Permissible size deviation, mm +1.3 0.4 0 0.054 +0.059 +0.037 Surface roughness, µm Rа60 (Rz250) Rа20 Rа5.5 Rа2.5 Ra1.25
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Ministry of Education and Science of the Samara Region
GBOU SPO Togliatti Engineering College
Considered I approve
at the meeting of the MK Deputy. NMR Director
specialty 151901 __________ Lutsenko T.N.
Protocol No.______
"___" ___________ 2013 "___" ___________ 2013
Chairman of the MC
__________ /Bykovskaya A.V./
Control and measuring materials
in the discipline "Technology of mechanical engineering"
specialty SPO: 151901 Mechanical engineering technology
for 4th year students
Developed by teacher Ivanov A.S.
SPO specialty: 151901 Mechanical engineering technology
Discipline: Engineering technology
Section 1. Specification of training elements
№ p/p
Name of educational elements
(didactic units)
The purpose of training
must know
must know
must know
must know
must know
must know
must know
must know
must know
Schemes of technological adjustments
must know
must know
The norm of time and its structure
must know
must know
must know
must know
must know
must know
must know
must know
Machine assembly technology.
must know
must know
must know
must know
Section 2 Test items
Option 1
Block A
Task (question)
Sample response
№ tasks
Possible answer
1
1-C,2-A,3-B
Set the correspondence between the name of the surface and the graphic image
1 - B;
2 - B;
3 - A;
4 - G.
IMAGE
Surfaces:
A) main
B) auxiliary
B) executive
D) free
Establish a correspondence between the name and the designation of the separation
1 - G;
2 - D;
3 - A;
4 - B;
5 B.
Name
A) cylindricity
B) roundness
B) flatness
D) straightness
E) longitudinal section profile tolerance
Establish a correspondence, what types of directions of irregularities are indicated in the diagrams.
1 - B;
2 - D;
3 - G;
4 - A;
5 B.
Name of irregularities
parallel
crisscrossing
perpendicular
arbitrary
radial
Designation on the diagrams
BUT. G.
B. D.
The completed part of the technological process performed by a worker at one workplace is
operation
Serial production is characterized
the number of products does not affect the type of production
The criterion for determining the type of production is
the range of manufactured products and the coefficient of consolidation of operations
product release cycle
3. qualification of workers
precision in metalworking can be achieved by methods
the method of passages and measurements
on tuned machines
points 1 and 2
measurement of the machined surface
The minimum operating allowance for bodies of revolution is determined by the formula
surface roughness, not subjected to processing, IS SIGNED
1. 3.
2. 4. all of the above
The base used to determine the position of the workpiece during the manufacturing process is called
design base
technological base
main base
auxiliary base
Operational time is determined by the formula
T OP \u003d T O + T B
T DOP \u003d T SB + T OP
T PCS \u003d T O + T B + T ABOUT + T FROM
T W-K \u003d T PC + T P-W / N
The base that deprives the workpiece of three degrees of freedom is called
double support
installation
guide
The workpiece base, which appears as a real surface, is called
open
measuring
Determine the type of production, if the coefficient of consolidation of operationsTo W =1
small-scale production
medium batch production
large-scale production
mass production
The totality of all irregularities on the considered surface is called
non-straightness of the workpiece surface
surface waviness
not parallel surfaces of the part
surface roughness
The set of dimensions that form a closed contour and refer to one part is called
dimension line
dimensional chain
size group
dimensional link
Define the term - general allowance
Based errors occur if they do not match
design and technological bases
technological and measuring bases
design and measurement bases
When choosing finishing bases for processing in all operations, it is necessary to use
principle of combination of bases
base constancy principle
only installation bases
installation and design bases
The ability of a structure and its elements to resist external loads without collapsing is called
rigidity
sustainability
strength
elasticity
Block B
Task (question)
Sample response
Limited application of the principle of interchangeability and the use of fitting work is typical for ____________
single assembly production.
The main basing schemes in metalworking are _________________________________________________
basing of prismatic blanks, basing of long and short cylindrical blanks.
The degree of compliance of a part with a given size and shape is called ________________________________
processing accuracy.
The amount of movement of the tool in one revolution of the workpiece is called ___________________
According to the purpose, the surfaces of parts are classified into __________________________________________________
on the main, auxiliary, executive, free
The working drawing of the part, the drawing of the workpiece, the specifications, and the assembly drawing of the part are the initial data for the design _____________________________
technological process.
To compensate for the errors that arise when choosing blanks, __________________________________ is assigned
processing allowance.
A set of periodically alternating elevations and depressions with a ratio is called _____________________
surface waviness.
One of the dimensions that forms a dimensional chain is called ________________________________
dimensional link.
The assembly of blanks, components or products as a whole, which are subject to subsequent disassembly is called _________________________
pre-assembly
Option - 2
Block A
Task (question)
Sample response
Instructions for completing tasks No. 1-3: correlate the contents of column 1 with the contents of column 2. Write down the letter from column 2, indicating the correct answer to the questions in column 1, in the corresponding lines of the answer sheet. As a result, you will receive a sequence of letters. For example,
№ tasks
Possible answer
1
1-C, 2-A, 3-B
Match: These formulas are used to determine which part manufacturability analysis parameters
1 - G;
2 - B;
3 - A;
4 - B
Coefficient
A. Machining Accuracy Ratio
B. Coefficient of surface roughness
B. Material utilization rate
D. Coefficient of unification of structural elements
Establish a correspondence between the graphic designation and the name of the support, clamp and mounting device.
1 - B
2 - B
3 - A
4 - G
graphic designation
1. 3.
Name
A - collet mandrel
B - floating center
B - fixed support
G - adjustable support
Set the correspondence between the processing sketch and its name
1 - B
2 - G
3 - A
4 - B
Name
A. Parallel multi-tool single.
B. Sequential multi-instrument single.
B. Parallel-serial multi-tool single.
G. Parallel single tool single
Instructions for completing tasks No. 4-20: Choose the letter corresponding to the correct answer and write it down in the answer sheet.
- this is the formula for determining
piece time
main time
auxiliary time
technological norm of time
route map
process flow chart
operating card
technological instruction
machine tools, designed for the manufacture of products of the same name and different sizes
universal
specialized
special
mechanized
Determine the type of production if the coefficient of consolidation of operations K Z = 8.5
small-scale production
medium batch production
large-scale production
mass production
surface roughness formed by removing a layer of material is indicated by the sign
2. 4.
Mass production is characterized
narrow range of manufactured products
limited product range
a wide range of manufactured products
various range of manufactured products
– this is the formula for defining
cutting speed
minute feed
spindle speed
cutting depth
An object or set of production items to be manufactured at an enterprise is called
assembly unit
product
4. kit
Joints that can be disassembled without damaging mating or fasteners are called
mobile
detachable
one-piece
motionless
When planning the area in front of the machines, a working place is provided with a width
– this is the formula for determining
design tightness
preload in conjugation
temperature of mating parts
pressing force
Define the term - defective layer
a layer of metal designed to be removed in one operation
the minimum required thickness of the metal layer to perform the operation
a surface layer of a metal whose structure, chemical composition, and mechanical properties differ from that of the base metal
layer of metal intended to be removed during all operations
When basing a workpiece in a fixture according to technological bases that are not related to measuring ones,
clamping errors
installation errors
processing errors
basing errors
Single, not regularly repeated deviations from the theoretical shape of the deviation surface are called
surface waviness
macrogeometric deviations
surface roughness
microgeometric deviations
The error that occurs before the application of the clamping force and during clamping is called
basing error
installation error
clamping error
fixture error
To ensure high hardness of the working surfaces of the teeth of the wheels, a type of heat treatment is used
carburizing followed by quenching
nitriding followed by hardening
cyanidation followed by hardening
oxidation followed by hardening
the property of a product that allows it to be manufactured and assembled at the lowest cost is called
repair manufacturability
production manufacturability
operational manufacturability
manufacturability of the product
Block B
Task (question)
Sample response
Instructions for completing assignments No. 21-30: In the appropriate line of the answer sheet, write down a short answer to the question, the end of the sentence, or the missing words.
For a visual illustration of the technological process, use ____________________
thumbnail map
Automated process control systems, in which the development of corrective actions on the controlled process occurs automatically, is called ________________________
managers
Surface irregularities formed as a result of the impact of the cutting edge of the tool on the surface to be machined are called _________________________
microgeometric deviations.
Deformation and wear of machine tools, wear of cutting tools, clamping force, thermal deformation affect __________
processing accuracy
A product, the components of which are interconnected, are called ____________________________
assembly unit.
The technological process of manufacturing a group of products with common design and technological features is called ____________________________
When processing the basing surfaces of body parts, _________________________ is taken as the primary base
draft main holes
A part formed from a set of bushings interconnected by rods is called ______________________
Compliance with the exact compliance of the technological process of manufacturing or repairing a product with the requirements of technological and design documentation is called _________
technological discipline
Products that are not connected at the manufacturer, which are a set of products of an auxiliary nature, are called ______________________________________
kit
Section 3 Codification System
Name of didactic unit
Variant number
Question numbers
Technological processes of machining
4; 5; 6; 10, 14, 25
Machining precision.
Surface quality of machine parts
Selection of bases when processing workpieces
3, 12, 13, 18, 19, 22
Machining allowances
Design principles, rules for the development of technological processes
The concept of technological discipline
Auxiliary and control operations in the technological process
Calculations for the design of machine operations
Schemes of technological adjustments
Requirements for the development of settlement and technological maps for CNC machines
The norm of time and its structure
Methods of standardization of labor processes, standards for technical regulation
Organization of technical and regulatory work at a machine-building enterprise
Methods for processing the main surfaces of typical machine parts
Programming the processing of parts on machines of different groups
Technological processes, manufacturing of standard parts for general machine building applications
Technological processes for manufacturing parts in a flexible production system (FPS), on automatic rotary lines (ARL).
Automated design of technological processes
Machine assembly technology.
11; 12; 14; 25; 30
Methods of implementation, production debugging of technological processes, control over compliance with technological discipline
Product defects: analysis of causes, their elimination
Fundamentals of Designing Machine Shop Sites
Section 4 References
Averchenkov V.I. and etc. Engineering technology. Collection of tasks and exercises. – M.: INFRA-M, 2006.
Bazrov B.M. Fundamentals of mechanical engineering technology. – M.: Mashinostroenie, 2005.
Balakshin B.S. Fundamentals of mechanical engineering technology - M .: Mashinostroenie, 1985.
Vinogradov V.M. Engineering technology. Introduction to the specialty. – M.: Mashinostroenie, 2006.
Gorbatsevich A.F., Shkred V.A. Course design for engineering technology - Minsk: Higher School, 1983.
Danilevsky V.V.. Engineering technology. - M .: Higher School, 1984.
Dobrydnev I.S. Course design on the subject "Technology of mechanical engineering". - M .: Mashinostroenie, 1985.
Klepikov V.V., Bodrov A.N. Engineering technology. - M.: FORUM - INFRA-M, 2004.
Matalin A.A. Engineering technology - L .: Mashinostroenie, 1985.
Mikhailov A.V., Rastorguev D.A., Skhirtladze A.G. - Fundamentals of designing technological processes of mechanical assembly production. - T .: Togliatti State University, 2004.
Task 1.66 option 3.
Given: d (size of the base surface of the shaft) = 80-0.039 mm,
? (processing method accuracy) =60 µm,
Tizn (permissible bushing wear) = 10 µm,
A2 =50±0.080 mm.
Determine the executive dimension D of the centering sleeve, which ensures the specified accuracy of dimension A2 when milling a groove.
Solution.
An analysis of the installation scheme shows that the accuracy of the hole diameter of the centering sleeve D affects the accuracy of the dimension A2, specified from the axis of the workpiece to the surface to be machined. It can be seen from the installation diagram that the fixing error (?z) for the A2 size is zero. Based on this, as a starting point, we accept that the accuracy of the execution of the size A2: TA2 \u003d? bA2 + Tizn. + ?, where?bA2 = ТD + Smin + Td is the basing error of the А2 size. The components TD and Smin are unknown quantities.
Solving the equality with respect to these unknowns, we get:
(Smin + ТD) \u003d TA2 - (Td + Tizn. +?) \u003d 0.16 - (0.039 + 0.010 + 0.060) \u003d 0.051 mm.
From the tables of GOST 25347-82, we select the tolerance field of the hole so that the condition is met: Smin + TD ? ES.
Comparing the calculated value (Smin + TD) = 0.051 with the tabular value of the upper deviation of the hole (ES), I take the tolerance field G7 (), which can be taken as the executive dimensions of the sleeve:
D=80G7.
Task 1.67 option 3.
Given: mandrel material - steel 20X,
workpiece material - bronze,
E 1 (steel) \u003d 210 GPa
E 2 (bronze) \u003d 100 GPa,
?1(steel)= 0.3
?2(bronze)= 0.33
f bronze on steel = 0.05
u?1,2 (Rz1 + Rz2)
d=30+0.013mm
L = 40 mm
d1 = 70 mm
K = 2.0
Rz (mandrels) - 1.6
Rz (blanks) - 3.2
Рz = 240 H
Tlife=10 µm.
Solution.
The starting point for performing calculations is the condition KMres = Mtr,
where: Mrez = Pz - cutting moment when turning the surface
Мтр= lfp is the moment of friction of the contact surface of the workpiece with the mandrel.
p = - contact pressure on the mating surface.
Required minimum tightness: Ncalc. min=
When using a solid mandrel: c1=1-?1 > c1=1-0.3=0.7
с2= +?2 > +0.33=1.78
Ncalc. min===3.767
Taking into account the correction u for the height of the roughness crushed during pressing, we find the value of the measured interference:
Nmeas. min= Ncalc. min+u > 3.767 + 1.2 (1.6+3.2)=3.767+5.76=9.5 µm;
From the tables of GOST 25347-82, we select the shaft tolerance field so that
(Td+Nmeas. min +Tizn.)?ei, where Tizn. is the allowable wear of the mandrel.
In our case (13 + 9.5 + Tlife) ?ei.
For my version, tolerance fields of the shaft (mandrel) can be accepted
p5 () or p6 () with an allowable mandrel wear of 3.5 µm.
Then the mandrel dimensions are:
d=30p5()mm or d=30p6()mm.
Pressing force at the maximum tightness, taking into account the safety factor K=2: P=Kfp?dl,
p => p===15,
Р=2 0.05 15 3.14 30 40=5652N.
Problem 1.57 option 1.
Given: ?b=0.05 mm, ?h=0.01 mm, ?us=0.01 mm, ?c=0.012 mm,
Ng=3000pcs,
Workpiece: material - non-hardened steel, hardness - HB 160, base surface - cylindrical, Тl=0.2 mm.
Fixture: prism, Steel 20, hardness - HV 650, F=36.1 mm2, Q=10000H, L=20 mm.
Processing method - milling with cooling, ? (processing method accuracy) =0.1 mm, tm=1.95 min.
Determine the overhaul period of the device.
Solution.
We determine the allowable value [? and] according to the equations:
?y = + > ?y = + =
=0,051+
?y \u003d Tl - ?, > 0.051+ \u003d Tl - ?, >0.051+ \u003d 0.2-0.1>
> = 0.049 > [?i] = = 0.04644 mm = 46.44 µm.
The permissible number of workpieces to be installed [N] up to the wear limit of the setting elements of the fixture is found from the equation:
[N] = , from the reference book - we find m=1818, m1=1014, m2=1309, wear resistance criterion P1=1.03, correction factor taking into account the processing conditions Ku=0.9.
[N]====21716 pcs.
The overhaul period, which determines the need to replace or restore the installation elements of the device, is found from the equation:
PC = = = 73.8 months.
Problem 1.43
Given: D1 \u003d D2 \u003d 50 + 0.039 mm, dc \u003d dc \u003d 50f7 mm,
TL = 0.1 mm, ? (accuracy of the processing method) = 0.050 mm.
Determine the accuracy of the size 70 of the connecting rod head and the possibility of processing the surfaces of the connecting rod with a set of cutters, observing the dimensional accuracy of 45 + 0.4 mm.
Solution.
Based on the scheme for installing the workpiece in the fixture, the basing error when performing size 70 is determined by the equation:
?b70 = Smax=TD + Smin + Td = 0.039+0.025+0.025=0.089 mm,
Since the condition of the problem does not say anything about the errors in fixing and positioning the workpiece, then?z = ?p.z. = 0. Then
T70 = ?b70 + ? = 0.089+0.05=0.139 mm.
For size 45, a tolerance for the size between the axes of the holes is added (it could also affect size 70 if the fingers did not have the same tolerance field):
?b45 = Smax=TD + Smin + Td + TL = 0.039+0.025+0.025+0.1=0.189 mm,
T45 = ?b45 + ? \u003d 0.189 + 0.05 \u003d 0.239 mm.
As you can see, the calculated tolerance is 0.239< 0,4 мм допуска заданного, следовательно, мы можем применить набор фрез для обработки головки шатуна.
Literature:
1. Machine tools. Directory. / Ed. B.N. Vardashkina et al. M., Mashinostroenie, 1984.
2. Directory of a metal worker. / Ed. M.P. Novikova / M., Mashinostroenie, 1977.