Guidelines for the implementation of practical work on the discipline “PSiP”
The rational organization of the technological process is characterized by the principles of its rational organization. Knowing the level of implementation of these principles, the enterprise can predict its costs for the production of new types of products.
The purpose of this work is to familiarize with the methodology for calculating indicators that characterize the principles of the rational organization of the technological process, as well as with the methodology for determining the integral assessment of the rational organization of the technological process and analyzing it using the example of machine assembly (SP-2).
Calculation of coefficients characterizing the principles of rational organization
Since the production process is a space-time category, its ideal construction involves minimizing the space and time costs for the transformation of all initial resources into the necessary products. Therefore, the principles of an ideal manufacturing process can be understood as principles aimed at saving time and space in its design.
The organization of the production process at any machine-building enterprise, in any of its workshops is based on a rational combination in time and space of all the main, auxiliary and service processes. Features and methods of this combination are different in different production conditions. However, with all the diversity of the latter, the organization of production processes must be subject to certain general principles: batching, specialization, proportionality, rhythm, continuity, parallelism, direct flow, flexibility and automaticity.
The level of implementation at the enterprise of the principles of rational organization of the technological process can be assessed through a system of indicators (coefficients). Consider, using the example of the production cycle of manufacturing the SP-2 machine, how these coefficients are calculated and compare them with the characteristics of the “ideal” technological process.
The cycle graph reproduces the assembly diagram, taken on a time scale, in relation to the manufacture of 30 SP-2 machines; for comparison, the production cycles of individual parts are also shown.
This principle follows from the condition of saving time as a measure of labor costs and increasing the productivity of processes. Any operation can be conditionally divided into three main stages:
– process preparation;
– implementation of the main stages;
– implementation of auxiliary steps.
When a worker has new jobs, a large amount of time is associated with the preparation of the process, familiarization with the work, preparation of the workplace, etc. At the same time, a person needs much more time to issue the first copies than is allotted according to the norms, this is due to the fact that a person must adapt to work.
With a large proportion of manual work on complex operations, this total time can reach very large values. Consequently, the highest productivity of the production process is achieved when processing the item in batches, so the coefficient characterizing this principle can be written:
where K PAR is the partion coefficient;
t PRIN – adjustment time;
t PZ – preparatory and final time;
N is the batch size.
At a high level of automation, the time for adapting a worker to a new operation is reduced to memorizing the sequence of pressing start-stop buttons and practically reduces to 0. The boundary value of the partion coefficient (K PART ) in automatic modes of processing a batch of parts will be determined by the formula:
where q i is the number of shifts in the operation of the i-th group of equipment involved in a particular technological process;
m i – the number of pieces of equipment allocated for the implementation of the i-th private technological process.
The distribution of equipment for private production processes (by operations) is carried out by students in accordance with the availability of available equipment and the total time for processing a batch of parts for the i-th operation. (Annex 1 and 3).
The preparatory and final time is taken according to the standards of the equipment operation mode.
The time for processing parts is calculated based on formula 2.3.
where t i is the time to complete the i-th part. The value of t i is determined for the first parts until t i becomes equal to the value of t H , i.e. t i u003d t N ;
t MAX – the maximum time to perform the operation, as a rule, this time value is equal to the actual time of the first part;
b – coefficient characterizing the share of manual labor in the norm of time;
i is the serial number of the part in the lot.
The maximum value of the operation is equal to the execution time of the first part, i.e. t MAX = t 1 . The standard time for processing the operation (t H ) is determined according to the cycle schedule as the ratio of the total time to complete a batch of products, taking into account the coefficient of fulfillment of the norms, divided by the size of the batch of parts (Appendices 1, 4).
Standard time is determined by the formula:
t H = , (2.4)
where D p – the duration of the operation for the manufacture of a batch of products, days;
T SM – shift duration, hour;
q – the number of shifts in accordance with the mode of operation of the enterprise;
K VN – the coefficient of compliance with the norms (Appendix 4).
For each operation, the coefficient is determined – b according to Appendix 2. When calculating t i , the serial number of the part N i is taken with doubling the previous serial number of the workpiece (1, 2, 4, 8, etc.). Appendix 2 shows the coefficients for the maximum increase in the processing of the first part in relation to the standard duration.
K MAX = . (2.5)
The duration of the processing time of the i-th parts is determined until the value of t i becomes equal to t N , and the serial number of the workpiece for each operation may be different. Standard time is considered as minimal, but sufficient for their implementation in accordance with the requirements of the technological process. Time norms are determined for each operation from the maximum time value to the normative one.
Since the worker needs time to acquire skills in work, for this it is necessary to process a certain number of parts, then when processing part of the batch of parts, the worker’s work time exceeds the standard. Therefore, it is necessary to check whether the reserves provided for when planning the production of products according to the cycle schedule are sufficient (Appendix 1).
In this regard, the weighted average deviation per unit of product is found ( t) caused by the excess of actual labor costs in the processing of the first parts of the batch compared to the standard processing time for parts. The resulting deviation is compared with the reserve time (the soak time of the parts). The waiting time for parts between the end of this operation and the beginning of the subsequent operation is also determined per unit of output (Appendix 1).
Weighted average deviation per unit of output ( t) is determined by the formula:
t = , (2.6)
where t MAXi is the actual value of the execution time of the i-th part, which exceeds the standard value;
n i is the number of parts that have the same actual value;
n is the size of the part launch batch (to be specified according to the cycle schedule).
To determine the partion coefficient for the whole product, it is necessary to calculate the partion coefficients for each part, and then find the average value of these coefficients.
The calculation of the partion coefficient for the details of the second, third and fourth nodes is carried out similarly.
On what operations deviations from the planned terms of their implementation are possible and what can be done to maintain the rhythm of production.
The principle of specialization
Specialization is a form of social division of labor, which, developing systematically in industry, causes the separation and isolation of industries, enterprises, workshops, sections, lines and individual jobs.
This is the most important condition for saving labor in the production process. In this case, the production process is divided into simpler elements of the operation and assigned to individual jobs, thus simplifying labor movements, and it becomes possible to achieve high productivity with minimal time.
The maximum productivity of the process is achieved by dividing it into simple parts or operations and performing each of them by certain workers using certain tools. The best implementation of this principle is possible in mass and large-scale production, where it is possible to create specialized workplaces where only one operation is performed.
An indicator characterizing the level of specialization of the production process can be the ratio of the number of operations per unit of equipment.
where K SP – coefficient of specialization;
K O – the total number of operations in the process;
m is the total number of equipment with which the operations of the process are performed.
The machine park of the enterprise’s equipment is given in Appendix 3. The student is invited to distribute the available equipment among the operations of the technological process in proportion to the duration of the operation.
To what type of production can this production for the manufacture of the machine be attributed? What jobs can be specialized?
The principle of proportionality
The principle of proportionality characterizes the compliance of the throughput (productivity) of the workplace and the enterprise in accordance with a given plan.
Proportionality is a principle, the implementation of which ensures equal throughput of different jobs of the same process, proportional provision of jobs with information, material resources, personnel, etc.
The division of the process into simple elements and the implementation of each of them with the help of a certain group of workers and the corresponding tools of labor requires the establishment of strict quantitative proportions between their productivity. That is, the maximum productivity of the total technological process can be achieved with the same labor productivity of private processes (while ensuring their proportionality).
where P 0 – labor productivity of the aggregate process – is determined by the lowest labor productivity in one operation;
P 1 , P 2 , …P i – labor productivity of private processes (operations) per unit of time.
Non-compliance with the principle of proportionality is the cause of bottlenecks and disproportions, when the throughput of certain departments is insufficient to fulfill production tasks and hinders the further development of production.
The level of proportionality of production can be used in the development of recommendations for improving the integrated mechanization and automation of the enterprise.
The productivity of private processes P i shows how many parts are produced per unit of time on machines or on one machine, where work is performed on a specific operation on a part of the batch. As a rule, consider the hourly or daily productivity of the process.
P i = , (2.9)
where T i is the planned period of time for processing a batch of parts for a specific operation.
The planned period of time for the execution of the operation is determined according to the cyclic schedule by the formula:
T i = D R * T SM * q, (2.10)
where D R – the duration of the operation for the manufacture of a batch of products, days;
T SM – shift duration, hour;
q – the number of shifts in accordance with the mode of operation of the enterprise;
First, the coefficients of proportionality for each operation are determined, and then, as an arithmetic mean, the coefficients for the part, assemblies and for the machine as a whole are calculated.
What role does the principle of proportionality play in the organization of the technological process and what areas of work can an enterprise choose to improve the stability of the enterprise’s operating mode.
This principle suggests that the shortest duration of the production process is achieved with the complete elimination of interruptions in the performance of its individual operations in time.
A measure of the continuity of the process can be the ratio of the time spent on the direct processing of raw materials and materials into finished products to the time it passes through the process.
The continuity coefficient can be calculated for a simple and for a complex technological process. If we consider the technological process of manufacturing each part independently of the others, then such technological processes can be considered as simple. If we consider the technological process of manufacturing all the parts included in the machine, then such a technological process is calculated as complex.
The continuity factor for simple technological processes is determined by formula 2.11:
where K N is the coefficient of continuity;
t N i is the standard duration of the i-th operation;
K o – the number of operations required to manufacture the part;
T C – cycle duration.
For the duration of the cycle, here you can take the actual duration of the manufacture of the part, which is determined by the cyclic schedule.
The continuity factor for a complex technological process should apply formula 2.12:
where t ‘ Н i is the standard duration of the i-th operation for the part that has the maximum planned time;
K ‘ o – the number of operations required to manufacture the most labor-intensive part;
T ‘ C – the duration of the cycle from the start of the production of the most labor-intensive part batch to the completion of the assembly of the machine.
The required data is determined by a cyclic schedule.
When organizing the production process, it is necessary to implement the principle of continuity in order to reduce the duration of the production cycle and increase the proportion of time spent directly on the execution of the technological process.
How rational is the construction of the technological process in terms of continuity and suggest directions for the work of the enterprise to improve the technological process.
The principle of parallelism
The shortest production time is achieved when performing partial processes while processing several copies of the same parts in different operations, thus more parts are produced in a given period of time.
Parallelism is the principle of rational organization of processes, which characterizes the degree of overlapping of operations in time. Types of combinations of operations: sequential, parallel and parallel-serial.
Parallelism in the subassembly and general assembly means the simultaneous execution of assembly and assembly operations on the same or different objects. The possibility of applying the principle of parallelism in the assembly is largely determined by the rational division of the machine into nodes.
The parallelism ratio is defined as the ratio of the parallel execution time of partial processes to the total actual time. Determined by individual items or operations:
The coefficient of parallelism for individual items or parts is determined by the formula:
The parallelism factor for operations is determined by the formula:
where T MAX i is the processing time or the manufacture of the most labor-intensive item or part thereof;
t i , t MAXi is the processing time of the item at the i-th operation or the longest operation;
K O – the number of operations;
T ‘ C , T C – the duration of the manufacturing cycle of the entire machine and a separate part.
When organizing the production process, it is necessary to observe the principle of parallelism, ensuring, on this basis, a reduction in the duration of the production cycle.
How does parallelism affect the fulfillment of orders on time and the cost of manufacturing a machine? How do conditionally fixed and variable components in the cost price change?
The principle of rhythm
This principle says that the maximum productivity of the process can be achieved only with its rhythmic course, providing the same output for any identical period of working time at any stage of the process. This means that if in some i-th period of time, when the equality of productivity at the moment and the total productivity of the process (Pt i ≠ Pot) is not ensured, a breakdown occurs, then the total volume of products produced for the planned period of time will be less potential performance over the same period.
Пt i – actual performance for the i-th period of time
Pot – estimated (potential) performance for the same time
n is the number of segments for which the volume of output is determined.
Rhythm is the principle of rational organization of processes, which characterizes the uniformity of their implementation in time.
When organizing the production process, it is necessary to strictly observe the principle of rhythm, ensuring the release of products on schedule based on the uniform progress of production, as well as its timely preparation and comprehensive service.
The productivity of the process is considered as the volume of output (products or parts-sets) for a separate operation per unit of time (for example, a shift), which can be determined by the formula:
Пt i = , (2.16)
where T SM is the duration of the shift, hours;
m t – the number of machines currently working on the operation, (to simplify the calculations, consider the number of machines working on the operation unchanged) pcs.;
q is the number of equipment operation mode changes;
t H is the standard duration of processing the operation, n-hour.
The rhythmicity of the release can be considered both in detail and in the car as a whole.
The potential (calculated) productivity of the release of parts for an operation will be determined by the smallest partial productivity of the process.
Rhythm coefficient of production of machines is determined by the number of assembled machines during the shift to the planned release.
Show the relationship between the rhythm of production and production management.
Direct flow principle
Time and space savings in the product manufacturing process are also achieved by arranging the individual production units in a sequence of partial processes one after the other, thereby reducing both the space and time required to move the product from one stage to another, as well as the labor expended for these transitions.
This is another condition for the organization of ideal production, which is called the rule or principle of direct flow.
It is defined as: the maximum reduction in distance, time and costs for the movement of objects of labor in production, and the maximum implementation of the principles of continuity and parallelism of processes is achieved when subdivisions for partial processes are located in close proximity to each other in the order of their execution sequence, i.e. when organizing the direct flow of the process.
A measure of the directness of the process can be the coefficient (K PT ), characterizing the ratio of the total distance of movement of objects of labor between jobs located one after another in the order of the sequence of operations (S) to the actual distance of movement (S f ), i.e.
K PT = a1. (2.17)
In the absence of actual data, it is very difficult to calculate the direct flow factor. But it can be assumed that with a lack of equipment, return material flows of parts during heat treatment may occur, i.e. we are talking about heat treatment 2. If the average distance of movement of objects of labor between jobs is 6-10 meters, then by formula 2.17 it is possible to determine the coefficients of direct flow for individual operations and for the whole machine.
Show the relationship between the directness of production and the layout of the shop. What are the advantages and disadvantages of subject-closed areas?
The principle of automaticity
This principle assumes the maximum (taking into account technical feasibility and economic feasibility) execution of the operations of the production process automatically. The need for automaticity is usually due to the intensification of technological regimes, increased requirements for processing accuracy, an increase in program tasks and other conditions when mechanized, and even more so manual operations cannot provide the specified and increased indicators of the production process.
The coefficient of automaticity is calculated as the ratio of automated main, auxiliary, control and transport operations to the total number of operations:
where K AVT is the number of automated operations in the process;
K O – the total number of operations.
Since an automated process is a process where not only all the main operations are automated, but also auxiliary, control and transport ones, there are few such processes at our enterprises. Most often, along with the full automation of the main production, auxiliary and control ones have a considerable share of manual labor. Therefore, it is wrong to talk about the automation of the production process only as the automation of the main production.
The level of automation of production as a whole depends on the automation of private production processes (Appendix 5).
Show the relationship between the level of automation in the manufacture of a machine and the labor costs for its manufacture. How does the level of automation of production affect the social productivity of labor?
Principle of Flexibility
The principle of flexibility is the ability to quickly switch to the production of other products included in the production program of the enterprise, without significant loss of time.
Flexible automated production is a production that allows, in a short time and at minimal cost, on the same equipment, without interrupting the production process and without stopping the equipment, as necessary, switch to the production of new products of an arbitrary range within the technical capabilities and technical purpose of the equipment . The advantages of flexible production compared to traditional production are manifested in increasing the mobility of production, reducing the time for mastering new products, increasing labor productivity, reducing the production cycle and reducing production costs.
Therefore, one of the main characteristics of an agile manufacturing process is changeover time. By this time, you can evaluate the flexibility of the production process. The flexibility factor is similar to the automation factor. It can be calculated both for a piece of equipment and for the process as a whole.
K GIB = a 0, (2.19)
where t Ф i – time for equipment changeover during the transition to the production of the machine (Appendix 6);
t NAL – the maximum time for equipment changeover for a given group of equipment, which is determined by passport data (Appendix 6).