The main design value of the production line is the flow cycle. The production line cycle is understood as the time interval between two products produced one after the other from the last operation or between any adjacent operations. The flow cycle is a function of a given output program and significantly affects the choice of the technological process, equipment, tooling, and vehicles. AT general view the value of the cycle of the production line (T) is determined by the formula:
T \u003d Fpl / P, (16.1)
where Fpl - planned, useful fund of equipment operation time for a certain period of time, for example, a month or a year, in hours or minutes; P - production program for the same period of time in natural terms, in pieces, etc.
When determining the planned useful fund of equipment operation time, it is necessary to take into account the time required for equipment repair, tool change, for setting up machine tools, as well as time for rest, the natural needs of workers, while laying the basis for a scientifically based work and rest regimen during the working day.
A scientifically based work and rest regimen improves the physiological functions of workers, significantly increases labor productivity, the quality of work while reducing fatigue and improving the general well-being of workers.
The economic content of the production line tact is that if this calculated value of the tact is actually maintained on the stream, then the team of workers will definitely fulfill the established planned target, since the equipment and workers work with the planned productivity. With a reduction in the duration of the flow cycle, the production process is intensified either through the use of unaccounted for in the organization of the production line of the reserves for accelerating the operation of the equipment, or through the intensification of the labor of workers. With an increase in the duration of the cycle of the production line, the pace of production slows down, as there are losses of working time, and the equipment is underloaded, as a result, the production task will not be completed, which will lead to a deterioration in the technical and economic performance of the site, workshop, enterprise.
When transferring parts piece by piece from operation to operation, the period between the transfer of two successive parts is equal to the set cycle. When transferring parts from operation to operation by transfer mini-batches (Pp), for example, when the dimensions of the part are very small or when the tact value is measured in seconds, the rhythm of the production line (P) is calculated using the formula:
P \u003d T * Pp. (16.2)
where Pp is the value of the transfer mini-batch of parts. Compliance with the tact or rhythm of the production line is ensured by synchronizing the duration of each operation, that is, by aligning all technological operations in time with respect to the tact or rhythm of the flow.
The cycle is the basis for the calculation of other indicators of the production line. The calculation of the number of production line jobs (Kr) for each operation is made according to the formula:
Kp \u003d Tsht / T, (16.3)
where Tsht is the labor intensity of the production line operation in the same units as the flow cycle.
With full synchronization of the flow, the calculated number of jobs is always an integer, the equipment is fully loaded, i.e., the duration of the operation is equal to a cycle. During partial synchronization on non-synchronized operations, the calculated number of seats is not equal to an integer, so the result of the calculation of the number of seats is rounded up. This will be the accepted number of jobs (Kp). The workplace load factor (K3) for each operation is determined by the formula:
K3 = Kr/Kp. (16.4)
The conveyor speed of the production line (Sk) must correspond to the cycle of the flow. This correspondence is achieved if a path equal to the distance between two adjacent parts is passed by the conveyor in a time equal to the flow cycle:
Sk = Shk / T , (16.5)
where Shk is the distance between two parts processed one after another on the conveyor (conveyor step).
At machine-building enterprises, the conveyor speed ranges from 0.1–4 m/min. With more high speeds assembly line work can be dangerous for workers. Rational speeds of the working conveyor are considered to be 0.5-2.5 m/min when assembling relatively small objects.
One of the most important continuity conditions production process is maintenance at all stages mass production a certain amount of production reserves. Production reserves are understood as work in progress in physical terms: blanks, semi-finished products, finished parts, assembly units located at different stages of the production process (at different levels readiness) and designed to ensure uninterrupted operation.
Production reserves are one of the main parts of the working capital of the enterprise. In this regard, ensuring the continuity of in-line production with the minimum possible working capital is an extremely important condition for increasing the efficiency of production. The size of production reserves, and, consequently, the amount of necessary working capital depends on the organizational construction of the production line, the arrangement of jobs, and the features of the equipment used. Determination of the value of production backlogs should be made on the basis of a special calculation, and then accounting and control of the state of backlogs should be kept.
Technological backlog (Ztech) is understood as parts or assembly units that are in the process of direct processing or assembly at workplaces, as well as parts that are subject to technological control at special workplaces of Quality Control Department (Kkon):
Ztech \u003d SKp * Kch + Kkon, (16.6)
where Kch is the number of parts processed simultaneously at one workplace.
The economic significance of the technological backlog is that if at the beginning of the work shift or at any hour of the production line at each workplace there is an estimated number of units of objects that have been processed according to previous operations, then there are conditions for working without downtime for workers and equipment, the planned shift task will be carried out, and, consequently, the calculated efficiency of the production line will be ensured. If at the beginning of the shift at any workplace there is no part, then in turn there will be downtime for workers and equipment at all subsequent operations after the “empty” workplace, equal to the cycle of the production line multiplied by the number of missing parts. As a result, the efficiency of the production line will decrease.
The transport backlog is understood as the total number of parts that are constantly in the process of moving between the workplaces of the production line. The value of the transport backlog (Ztr) of the production line is determined by the formula:
where P is the number of parts simultaneously transferred from operation to operation.
The economic value of the transport reserve coincides with the value of the technological reserve. If there is an estimated number of parts (assembly units) that have been processed according to previous operations on the working part of the conveyor during the shift, the work of people and equipment without downtime is ensured, since at strictly defined intervals equal to the cycle of the production line, each workplace will be delivered in a timely manner move detail. If there is no part on some transport device of the conveyor, then an “empty” transport device will approach a certain workplace of the production line and this workplace and all subsequent ones will be idle in turn for a time equal to the thread cycle.
The interoperational turnaround is understood as the number of parts that is necessary to ensure the smooth operation of adjacent workplaces with different productivity. Therefore, backlog is created when adjacent operations of the production line are not synchronized, and the duration of one of these operations is necessarily greater than the cycle of the production line. In such cases, by the beginning of the shift (or working day) after the workplace of the production line, where the duration of the operation is longer than a cycle, there should be a stock of parts that have been processed for all previous operations, including more labor-intensive ones. The backlog is determined between two adjacent operations. The turnover reserve during the shift continuously changes from its highest value at the beginning of the shift to the minimum value equal to zero, then it must again reach the maximum value. Thus, the turnover reserve must be constantly replenished before each shift or working day. It is possible to create a backlog for several working days in advance, however, this will increase the size of the related in work in progress working capital to slow down their turnover.
The interoperational turnover reserve (Zo6) can be defined as follows:
, (16.8)
where Rper is a regulated period for which the working capital is determined, for example, a shift (8 hours); Tkor - the duration of a short operation between two adjacent ones, min; Kp - cycle duration, min; Tdl - the duration of a long operation between two adjacent ones, min.
The reserve (insurance) backlog is the number of parts stored in stock, necessary to ensure the continuity of the production line in the event of a production process stop due to equipment breakdown or in case of untimely supply of semi-finished components. These reserves are important in the conditions of in-line production, since their absence can lead to disruption of the continuous, rhythmic work of many jobs in the stream. However, it does not follow from this that it is advisable to create insurance reserves for each operation of the production line, since this will significantly increase the amount of working capital associated with work in progress, and, consequently, will sharply reduce the efficiency of the in-line method of organizing production. Typically, such backlogs are created to ensure the uninterrupted operation of certain critical sections of production lines where high production stability has not been achieved, or after operations performed on equipment that often fails. The need for an insurance reserve is determined based on the experience of the production line.
The reserve (insurance) reserve is determined by the formula:
Zstr \u003d Tper / T (16.9)
where Tper is the time of a possible break in work on a given operation (established empirically).
Insurance and turnover backlog to a certain extent are interchangeable. So, if there is a working reserve in front of any two workplaces of the production line, which ensures the work of all other workplaces of the production line during the shift, then there is no need to have an insurance reserve.
After calculating the main indicators of the production line, they draw up a plan-schedule of the line, which is called the standard-plan.
Mass production called a progressive form of organization of production, based on the rhythmic repetition of the main and auxiliary operations coordinated in time, performed at specialized workplaces located in the sequence of the technological process.
From this definition it follows that the flow production is characterized by the previously considered principles of organizing the production process, primarily the principles of specialization, direct flow, continuity, parallelism and rhythm.
The principle of specialization
The principle of specialization in the conditions of in-line production is embodied in the creation of subject-closed sections in the form of specialized production lines designed to process one product assigned to a given line or several technologically related products.
Therefore, each workplace of the line must be specialized in the performance of one or more operations assigned to it.
When assigned to a line of one product, it is called one-subject.
Such lines are typical for mass production.
When attaching several products to the line (which may be necessary with little laboriousness of processing or with small program tasks), the line is multidisciplinary.
Such lines are typical for series and mass production. For multi-subject lines, products are fixed in such a way that they can be processed with minimal loss of time for equipment changeover with sufficient loading of jobs and full coincidence of operations.
Direct flow principle
The principle of direct flow provides for the placement of equipment and jobs in the order of the operations of the technological process.
The production line is the primary production site. Distinguish simple a chain of jobs on the line, where each operation has only one job, and complex if there are two or more backup places at the operations.
The configuration of production lines, depending on the conditions, can be straight, rectangular, circular, oval, etc.
Continuity principle
The principle of continuity on production lines is carried out in the form of a continuous (without interoperational lying) movement of products through operations with continuous (without downtime) work of workers and equipment.
Such lines are called continuous flow.
In those cases where there is no equality of performance in all operations, complete continuity is not achieved and such lines are intermittent flow or direct-flow.
The principle of parallelism
The principle of parallelism in relation to production lines is manifested in the parallel form of batch movement, in which products are transferred through operations individually or in small bundles. Therefore, in every this moment on the line, several units of this product are processed, which are at different stages of the process. With strict proportionality, a full and uniform loading of jobs on the line is achieved.
The principle of rhythm
The principle of rhythm in the conditions of mass production is manifested in the rhythmic release of products from the line and in the rhythmic repetition of all operations at each of its workplaces.
Figure 1 shows the main features that determine organizational form production line.
Figure 1 - Classification scheme for the main types of production lines
The main types of production lines used in mechanical engineering by degree of specialization are:
· continuous flow;
· discontinuous flow (direct flow).
On continuous production lines with a piece the transfer of products, the release (launch) of each item is carried out through the same time interval, called tact of the line(or piece rhythm).
The beat of the line r strictly consistent with production program and is calculated by the formula:
where - the actual fund of the line operation time in the planned period (month, day, shift), min.;N – production program for the same period, pcs.
On continuous production lines with the transfer of products transport parties the rhythm of the work of a continuous-flow line is characterized by a time interval separating the release (launch) of one pack from the next one, i.e. the rhythm of the line:
where R - the number of products in the lot (pack).
Thus, for each rhythm on the line and workplaces, the same amount of work is performed in terms of quantity and composition.
On discontinuous (once-through ) lines with their characteristic different performance on individual operations there is no continuity; however, the rhythm of release here can and must be respected.
The rhythm of the line in this case is determined by the time interval during which the production of a set value is formed on the line, for example, hourly, half-shift, shift.
Way to keep the rhythm
According to the method of maintaining the rhythm, lines are distinguished:
· with free rhythm;
· with a regulated rhythm.
lines with free rhythm Dont Have technical means strictly regulating the rhythm of work. These lines are used in all forms of flow, and the observance of the rhythm here is assigned directly to the workers of this line.
lines with a regulated rhythm characteristic of continuous-line production. Here the rhythm is maintained with the help of conveyors or light signaling.
Method of transporting objects of labor
The following vehicles are used to transport objects of labor in mass production:
· continuous transport equipment (driven conveyors of various designs);
· driveless (gravity) vehicles(rollers, slopes, descents, etc.);
· lifting and transport equipment of cyclic action (overhead and other cranes, monorails with hoists, electric carts, forklifts, etc.).
Conveyors are most widely used in mass production. They have significant benefits :
· maintain the rhythm of the line;
· facilitate the work of the worker;
· provide the ability to monitor the movement of backlogs;
· reduce the need for support workers.
It is necessary to distinguish between working and distribution conveyors.
Working conveyors designed to perform operations directly on their bearing part. Continuous motion work conveyors, such as auto-assembly conveyors, allow these operations to be performed while the conveyor is in motion.
If, according to the requirements of the technological process, operations must be performed with a stationary object, conveyors with pulsating motion are used. In this case, the conveyor drive is automatically switched on only for the time necessary to move the products to the next operation.
Distribution conveyors they are used on production lines with operations performed at stationary workplaces (for example, on machine tools) and with a different number of backup workplaces at individual operations, when, in order to maintain rhythm, it is necessary to ensure that the objects of labor are clearly addressed to workplaces at process operations.
2. Features of the organization of continuous production lines
Synchronization of operations
The operation of a continuous flow line is based on matching the duration of operations with the line cycle. The duration of any operation must be equal to or a multiple of a cycle.
The process of matching the duration of operations with the cycle of the production line is called synchronization .
The synchronicity condition can be expressed as follows:
where t– norms of time for process operations, min; FROM- the number of jobs per operation.
Synchronization is carried out by changing the structure of operations and organizational conditions for their implementation.
There are two stages of process synchronization:
1.Preliminary synchronization performed during the design of lines;
2.The final synchronization, carried out during the debugging of the line in the workshop.
Pre-Synchronization is achieved by selecting the method of performing operations, equipment and technological equipment, processing modes and the structure of the operation. In operations with a large amount of manual time, such as assembly, synchronization is achieved by recomposing transitions.
At the first stage, it is not always possible to ensure complete synchronization of the process; during this period, deviations in the loading of jobs by 8≈10% are allowed.
This overload should be removed when debugging the line by introducing organizational measures that increase labor productivity at overloaded workplaces, i.e. at final synchronization process.
Among such measures are the use of small-scale mechanization, the forcing of technological regimes, the introduction of high-performance equipment, the rational layout of the workplace and the improvement of its maintenance, the individual selection of workers for overloaded operations, as well as material incentives to increase labor productivity in these operations.
When synchronizing the technological process, one should take into account the conditions for performing operations on the line, i.e. the nature of transportation (continuous movement of the object or pulsating), the size of the transfer batch, the place of operations (with or without removal of the product from the conveyor), etc., since these conditions affect the structure and magnitude of the rhythm.
So, for example, with a single transfer of products to workplaces, continuous movement of the conveyor and performing work on the conveyor itself the rhythm of the line operation will correspond to the calculated one and coincide in duration with the norm of time for the operation, since the transportation time is overlapped by the time of the operation itself, and installation and removal of the product are not required.
But if, under the same conditions, the operation is performed on stationary workplace , in the rhythm of the line should be taken into account the time of transportation t tr(if it does not overlap), withdrawal time t sn and installation t mouth products and processing time t arr:
.
The synchronism of the technological process creates the prerequisites for work with a regulated rhythm and for the use of mechanized means of continuous transport.
At partially synchronized processes , i.e. processes with significant fluctuations in the actual time spent on operations, create continuous production lines with free rhythm .
Maintaining the rhythm on such lines is achieved mainly by mechanization and maintaining a stable performance of the equipment in the main operations. For continuous work at the workplace, a small reserve reserve (stock) of semi-finished products is created. On lines of this type, any vehicles can be used.
If the duration of each operation is equal to tact (for piece transfer of products) or rhythm (for batch transfer of products), then it is enough to have one workplace for each operation, and the products will be transferred from the previous workplace to the next one at the same time interval.
If the duration of the operation is a multiple of a cycle, then at the parallel workplaces of each operation, several products will be processed simultaneously.
Fundamentals of calculation of continuous production lines
The initial data for the calculation of continuous production lines are:
· line production program for a certain period of time (month, decade, day, shift)Nout;
· launch program for the same periodNzap;
· appropriate time funds.
Daily launch program N zap determined by the daily release program:
where a - the percentage of technological losses, for example, in connection with the manufacture of test parts when setting up equipment or the consumption of parts for control purposes.
Daily valid fund of line operation time F d taking into account the regulated breaks for rest T p equals:
where F to – calendar fund working time per shift, min; S- the number of shifts per day.
The initial design standard in the design of a production line is its cycle r(with batch transmission - rhythm), which should ensure the implementation of a given program for a planned period:
Number of jobs C i on the i-th operation equals
where t i is the time limit for this operation.
Number of workers-operators R taking into account multi-machine service, is determined by the formula
where b is the percentage of the additional number of workers in case of absenteeism (holidays, performance of public duties, illness, etc.); m– number of operations on the line; i- the rate of maintenance of jobs in this operation.
Conveyor speed Vk must be coordinated with the cycle of the line:
where lo- conveyor step, m (i.e. the distance between the axes of adjacent products or packs evenly spaced on the conveyor).
The speed of the conveyor should ensure not only its specified performance, but also the convenience and safety of work.
Range of the most rational speeds 0.1 – 2 m/min.
On continuous production lines are created backlog three types:
· technological;
transport;
· reserve (insurance).
Technological backlog corresponds to the number of products that are in the process of processing at the workplace at any given moment. In case of piece transfer, the technological reserve Z tech corresponds to the number of jobs FROM, i.e.
Transport backlog Z tr consists of the number of products that are in the process of being transported on the conveyor at any given moment. When piece-by-piece transfer of products from the previous workplace directly to the next backlog is equal to:
.
The transport backlog can also be determined based on the value of the conveyor step:
where L slave- the length of the working section of the conveyor, m.
Spare (insurance ) hurt It is created at the most critical and unstable operations in terms of execution time, as well as at checkpoints.
The value of backlogs is set on the basis of an analysis of the probability of deviations from a given work cycle at a given workplace (an average of 4-5% of a shift task).
The lack of parts is filled during periods of regulated breaks, after hours, or at off-line production areas.
The main types of continuous flow production lines are:
· with working conveyors;
· with distribution conveyors;
· flow-automatic;
· with a stationary object (stationary flow).
Continuous production lines with working conveyors are used mainly for assembly and finishing of products with sufficiently large program tasks.
Operations are performed directly on the conveyor; workers - operators are located along its bearing part, on one or both sides in the order of the operations of the technological process.
Products on the conveyor are installed and fixed at equal distances l about from each other.
The section of the working conveyor on which each operation is performed at a constant speed of the conveyor is called operating area.
In some cases, continuous production lines with working conveyors are characterized by a free rhythm.
To maintain the rhythm of work at a given speed of the conveyor, the boundaries of the working areas for operations are marked on its fixed part or on the floor with special signs, as shown in Figure 2.
Figure 2 - Scheme of the layout of the production line with a working conveyor
Workers, following the product, move along the zone, starting the operation at the beginning of the zone, ending it at the end, and then returning to their original position.
Continuous flow lines with distribution conveyors they are mainly used in areas of machining, finishing and assembly of small products with large program tasks. Operations are performed at stationary workplaces. Products are removed from the conveyor and at the end of the operation are returned to it.
Workplaces are located along the conveyor from one (Figure 3) or two of its sides.
Figure 3 - Scheme of the layout of the production line with a distribution conveyor
Products are evenly placed on the carrier part of the conveyor on hangers, trolleys, carriages or on belt sections marked with signs. With simple chains of workplaces, when the operation is performed in one step, each product that has approached the workplace must be processed before the next one arrives.
With complex technological chains, the duration of operations is different and equals two, three, four, etc. beats. Under these conditions, for the rhythmic issuance of products, it is necessary that, while working continuously, each subsequent workplace performs an operation with a shift of one cycle from the previous one.
For this purpose, automatic distribution of products or marking of the distribution conveyor is used. Marking signs (colored flags, letters, numbers, color designations) are applied to the divisions of the carrier body of the conveyor and are assigned to individual workplaces in the required sequence and quantity.
The minimum required set of marking marks on the line corresponds to the smallest multiple of the number of jobs on all line operations and is called the number of the period of the distribution pipeline P.
A set of marking marks can be repeated on the total length of the bearing part of the conveyor. Each marking sign passes by each workplace through the same time interval (period) T n, equal to
Marking signs of the conveyor are assigned to the workplaces at each operation in accordance with its duration.
The most convenient periods are 6, 12, 24 and 30. For long periods, it is recommended to introduce a two-row (differentiated) marking, using two sets of marking marks (for example, color and digital).
3. Features of the organization of discontinuous production lines
Regulations for the operation of discontinuous-flow (straight-through) lines
This form of in-line production is used in the processing of labor-intensive parts using different types of equipment. Technological operations on direct-flow lines are not synchronized. Due to the different complexity of operations on these lines, interoperational backlogs arise, which is an indicator of the discontinuity of the process.
To ensure smooth operation on such a line, it is necessary to establish the most appropriate work schedule, which should include:
· size of the enlarged rhythm;
· order of work at each workplace;
· the sequence and frequency of the transition of part-time workers on the serviced machines;
· the size and dynamics of working capital.
When choosing an enlarged rhythm of a direct-flow line, it is necessary to take into account the frequency of transferring the products of this line to subsequent sections; requirements rational organization labor for part-time workers (frequency of transitions), as well as the optimal amount of backlog.
For the calculation and organization of the line, a schedule of its work is drawn up.
Such a simplified schedule is shown in Table 1.
Table 1 - Schedule
|
Technological process |
Work- |
Schedule of equipment and workers during the rhythm period |
|||||||||||||||||||
|
N |
t w,, |
C pr |
N |
% per |
|||||||||||||||||
|
1,19 |
1 |
100 |
|
|
|||||||||||||||||
|
0,69 |
|
||||||||||||||||||||
|
1,31 |
|
|
|
|
|||||||||||||||||
|
0,81 where F d. cm- the actual fund of time for the shift, min; N cm- replaceable launch program, pcs. For this line r pr= 1.6 min. AT this example(table 1) it is taken equal to 1/4 shift, i.e. R = 2 h = 120 min. Underloaded machines at the 1st and 4th operations of this line can be served by one part-time worker B, at the 2nd and 3rd operations - worker C. Combined works can be performed only in the established sequence, which is what the line schedule provides. In related operations, due to their different labor intensity, interoperational backlogs are inevitable. In accordance with the accepted mode of operation, they will change during each rhythm (in this case within 2 hours) from zero to maximum (Figure 4).
Figure 4 - Dynamics of the backlog between two adjacent operations Calculation of interoperational working capital This backlog between adjacent operations is defined as the difference in the number of products processed in these operations for a certain period of time. Maximum backlash Zmax per certain period T can be calculated using the formula
where T- the period of work on related operations with a constant number of working machines, min; FROM is the number of pieces of equipment operating on adjacent i and i+1- operations during a period of time T; t w, t w+1– norms of time for these operations, min. | |||||||||||||||||||||
Flow method of organizing production
Some issues related to the organization of labor of workers on the production line were considered earlier in the topic of labor cooperation, it was about ways to ensure the interconnected work of performers. There is a lot in common in the topic of conveyor production, since the conveyor is one of the varieties of in-line production.
The experience of enterprises shows that the main socio-economic tasks of a scientific organization in mass production remain the establishment of an optimal labor content operations, rational placement of workers on the production line, synchronization of equipment and workers. Let us consider these issues in more detail, and as an object we will take a production line consisting of metal-cutting machines, the most common in mechanical engineering.
First of all, the question arises about the depth of the technological division of labor. Unlike conveyor assembly, more difficulties arise here, since we are dealing with specialized equipment, and therefore there are purely technological restrictions for the consolidation (or, conversely, downscaling) of operations.
Differentiation of technological processes is expedient up to such limits, while the amount of time spent on the installation and interoperational transportation of parts does not exceed the gain in time as a result of equipment specialization. In the future, the growth of labor productivity can only be ensured through the use of fundamentally new equipment - modular machines, automatic lines, reducing the time of interoperational transportation and installation, performing many other auxiliary activities. But such a technique also requires a new arrangement of workers, in connection with significant change in the content of labor and often a new professional composition of workers serving such lines.
So, let's consider the issues of placement of workers on the production line according to workplaces. The purpose of such an arrangement is to ensure that their workload is as evenly distributed as possible.
This is quite a difficult task. First of all, it is necessary to answer the question of how many workers should be on the production line. For example, let's carry out some calculations: the release program is 1600 pcs. Hence the line cycle 480: 1600 = 0.3 min. If the complexity of processing, suppose, is about 55 minutes, then the total number of operations should be at least 180 - 200 pcs. with a duration of 0.25 - 0.3 min. Consequently, the estimated number is 180 - 200 workers. But with such a duration of the operation, the work of the workers would be rather monotonous and tedious.
But you can also go the other way. Instead of one line for this output volume, for example, three production lines can be created, and then the average duration of an operation for workers on each of the lines can be increased to 0.9 minutes, and the total number of operations will be 60 - 70. With six lines, these figures will be 1.8 minutes, respectively. And 30 - 37 pcs. If, however, nine parallel operating lines were created, then the line cycle would be 2.7 minutes, and the number of operations on each of the lines would be 20 - 25.
The estimated number of workers in all cases is approximately the same (about 200 people). The total length of 3, 6 or 9 lines is not much more than one, but the content of labor, the level of training of personnel, their qualifications will be different. The recruitment of workers and the stabilization of the site team will also be different in difficulty.
The second problem of placement: on the basis of what, what data to conduct it in order to ensure a uniform workload of workers: on the basis of normative data on the time spent on the operation or on the basis of the actual data required to perform the operations assigned to the workers. The differences are that the actual duration of the operation and the normative due to the different productivity of workers are not the same, i.e. they are the same length. Consequently, the actual workload of workers will be far from uniform. Synchronicity in work within the framework of the collective labor process, some workers will hold back others, there may be downtime while waiting for the completion of work on the previous operation.
Therefore, you can first study the actual time spent (for example, based on the preliminary placement of workers), and then find a more optimal one.
It is also possible to act in a different way, instructing younger, less experienced workers with operations lasting less than a tact, and more experienced workers with more than a tact. For example, the line cycle is 1 minute. Then it will be possible to entrust an inexperienced worker with an operation with a standard duration of 0.8 minutes, and a more experienced worker with sufficiently developed production skills - with a duration of 1.2 - 1.3 minutes. But taking into account the underfulfillment of the norms by one and the overfulfillment of the norms by the other, both will actually spend about 1 min on their operation, i.e. correspond to the line operation.
This is one of the features of the arrangement, which must be taken into account in order to:
Ensure synchronous interconnected work of workers;
To create an opportunity for the gradual promotion of the worker as he accumulates production experience without disturbing the rhythm of the work of the entire team;
Reduce the monotony of work.
Therefore, if the arrangement of equipment on the production line is more or less stable, then the composition and arrangement of workers changes quite often. In conditions where a production line is characterized by a large variety technological equipment(and this ensures the possibility of processing the product from beginning to end within the site) the change there associated with the movement of workers from operation to operation is often associated with a combination of professions, which expands the production profile of the worker.
The workload of workers and fluctuations in its level for individual workers can also be influenced by a number of random factors (non-attendance of individual workers due to vacation, illness, replacement of one worker by another - brand new - during the period of his adaptation to a new workplace, etc.) Therefore, the organization of labor should provide a way out of the current situation. The paths are different:
Due to the so-called reserve workers;
When designing and organizing a production line, it is necessary to determine the product release program; choose the right equipment; set the main operating parameters of the line (tact, number of jobs, workers, step and speed of the conveyor); carry out planning and choose the transport line. Methodological issues of organization certain types mechanized production lines are considered in detail both in the educational (textbooks, collections of tasks) and in the scientific and technical literature, therefore, this chapter contains characteristics various kinds production lines and recommended calculations of the main parameters.
Allocate general parameters of production lines, characteristic of the entire set of lines, and private, which characterize the features of the organization of individual types. Guidelines to calculate the general parameters of production lines are presented in table 4.1.
Table 4.1. Calculation of general parameters of production lines
| Parameter name | Recommended formulas for calculations |
| Tact ( r) - the average period between the release of parts (products) from the last workplace on the production line or their launch at the first workplace | , where F eff - effective fund of line operation time in the planned period, min. (h); N- a program for the release or launch of products for the same planning period, PCS. |
| Launcher ( N h) |  where N c - production program (planned scope of work), pieces; b- inevitable technological marriage, percentage. |
| Tempo ( M) - productivity of the production line per unit time | , |
| Rhythm ( R) is a time interval that determines the release (launch) of one transport batch from another, following it | R=r p, where R- the size of the transport (transfer) batch of products, pcs. |
Continuation of table 4.1.
| Estimated number of jobs (С р i) on each operation; Accepted number of jobs per operation ( FROM etc . i) | , where t i- standard time to complete i- th operation; - accepted number of jobs per i-th operation (integer) |
| Equipment load factor for each operation ( To z.o . i) | |
| Average equipment load factor on the line ( To z.o.sr . ) |  , where m- the number of technological process operations performed on the line |
| The number of workers-operators on each operation ( R about . i) | , where N service. i- the rate of maintenance of workplaces for a worker on i th operation |
| The total number of operators on the line ( R about. common . ) |  , where b- the percentage of additional workers-operators to replace the main staff ( b≈2-3%)
|
Features of the organization of single-subject continuous production lines (ONPL) . Continuous production lines are characterized by the continuous movement of objects through the operations of the technological process with the continuous operation of workers and equipment at workplaces. ONPL are created for the manufacture of the same products over a long period using their parallel movement on operations.
The main condition for the organization of the ONPL is the synchronization of the operations of the technological process, i.e. the process of ensuring equality or multiplicity of the duration of all operations to the rhythm of the production line. This ensures equalization of performance across all operations of the stream.
There are preliminary synchronization (when designing a production line) and final synchronization (when debugging a line in working conditions). Preliminary synchronization allows the deviation of the duration of operations from the rhythm within ±5-10%, which must be eliminated during the final synchronization during the development and debugging of the line in production conditions.
If the estimated duration of the operation is greater than the flow cycle or a multiple of it, then the most effective measures to reduce the duration of the operation can be:
The use of multi-place fixtures and the simultaneous processing of several parts;
Use of mechanical and pneumatic clamps of parts;
Multi-tool setup;
Changing the operating modes of equipment;
Improving the manufacturability of the design.
If the duration of the operation is less than a thread tick or a multiple of it, the main direction of synchronization should be to keep the worker busy during the thread tick or a multiple of it. Consider, as an example, possible approaches to the synchronization of technological process operations when processing parts on machine tools.
Example. It is required to synchronize the technological process of manufacturing part A. The flow cycle is 1.2 min. The duration of technological operations is presented in table. 4.2.
Table 4.2. Technological process manufacturing part A
There is a significant underutilization of equipment in operations. Sequential maintenance of two machines by one worker is impossible, since the total duration of two operations is more than a cycle (1.7>1.2) and the deviation is more than 10%. With parallel service, this possibility is available. In this case, the synchronization condition for loading the worker is met, since the total employment of the worker in two operations is 1.1 min. (0.6+0.5), which is less than the flow cycle by 0.1 min. (deviation less than 10%).
In the conditions of in-line production, the norms of time and output should not be set for each workplace separately, but for the line as a whole. This is due to the fact that when setting individual time standards, the output of workers is not tied to the cycle of the flow, and thus an imbalance is introduced into the work of the line. At the same time, as shown by the workers, it fluctuates significantly - from 45 to 96%. Therefore, work on the calculation of norms and the placement of workers should be combined with a complex of organizational and technical measures aimed at increasing the degree of technological and organizational synchronization of the line, providing best use working time and equipment and the maximum possible output.
For such purposes, first of all, the cycle of the production line is calculated. Then it is determined lead time technological operations on each machine included in the production line. At the same time, the values of all factors affecting the time of operational work are indicated, the time for technical and organizational maintenance, rest and personal needs and the time of employment of the worker are calculated. All this is necessary for further work on line synchronization.
Each worker and their placement on the production line with the necessary measures to synchronize the line.
Technological synchronization measures are aimed at coordinating the processing time of a part on each machine with a given line operation cycle. They are provided mainly by carrying out technical measures to increase output on limiting equipment through the use of more productive cutting tools, increasing the number of simultaneously working tools, using multi-place fixtures and high-speed clamping devices, improving the quality of workpieces, automating the control process, optimizing cutting conditions, etc. d.
An increase in the degree of organizational synchronization is ensured by the establishment, on the basis of calculation according to the standards, of such an arrangement of workers on the basis of the organization of multi-machine jobs, in which uniform and complete them are achieved. To carry out organizational synchronization and placement of workers on the production line, a summary sheet is compiled (Table 12.5).
Table 12.5. Summary sheet for calculating the norms of time and norms of service at the workplaces of the production line (detail 70-1601021)
At the first stage, the operational time is calculated (section 1 of the map) for each of the operations performed on the line. At the same time, the task is to ensure technological synchronization of operations. The operating modes of the equipment are selected in such a way that the calculated value of the operational time is as close as possible to the tact time of the production line.
Further calculation is performed in the following sequence.
The reduced operational time for manufacturing the part for the operation is determined (column 11) according to the formula
If the operation is performed on several machines with the same operational time, the formula becomes:
The number of parts processed on machines where this operation is performed, for the maximum operational time, is found by the formula
If the operation is performed on one machine (n = 1 and T op max = T op i), then the number of parts processed for the maximum operational time is equal to one.
In cases where parts of two or more names with different programs are processed at the workplace, the conditionally reduced operational time for processing the main part is calculated:
The employment of a worker on each of the machines included in the workplace is determined (column 12):
T zi \u003d T v.n + T v.p + T a.n + T lane,
The time of active monitoring of the operation of the machine included in the workplace, depending on the sum of the machine-automatic time of all operations at the workplace, is determined from Table. 12.6.
| The sum of machine-automatic time of all operations included in the workplace | Time of active monitoring of the work of machines, min. | ||
|---|---|---|---|
| 0,10 | 0,005 | 4 | 0,084 |
| 0,20 | 0,009 | 5 | 0,100 |
| 0,30 | 0,012 | 6 | 0,114 |
| 0,50 | 0,018 | - | 0,126 |
| 0,75 | 0,022 | 8 | 0,134 |
| 1,00 | 0,025 | 9 | 0,144 |
| 2,00 | 0,046 | 10 or more | 0,150 |
| 3,00 | 0,066 |
The time for automatic approach of the tool is set (column 14 of Table 12.5). It is taken from the technical-normalization cards for the operation. Machine-automatic time is taken into account when its duration does not exceed the time spent by the worker on the transition to the next machine.