For the conditions of serial and small-scale production, the annual program for the release of the product is not carried out all at once, but is divided into batches. Lot of details- this is the number of parts that are simultaneously launched into production. The breakdown into batches is explained by the fact that the customer often does not need the entire annual program at once, but needs a uniform flow of ordered products. Another factor is the reduction of work in progress: if it is necessary to assemble, for example, 1000 gearboxes, then the production of 1000 shafts No. 1 will not allow to assemble a single gearbox until at least one set is available.

The batch size of parts affects:

1. On process performance and his cost price due to the share of preparatory and final work time (T p.z.) for one product

t piece-to. = t pcs + T p.z. / n , (8.1)

where t piece-to. - piece-calculation time for a technological operation; t pcs - piece time for a technological operation; n- lot size of parts. The larger the batch size, the less piece-calculation time for the technological operation.

Preparatory-final time (T p.z.) - this is the time to perform work to prepare for the processing of parts at the workplace. This time includes:

1. time to receive a task from the foreman of the site (operational map with a sketch of the part and a description of the processing sequence);

2. time to get acquainted with the task;

3. time to get the necessary cutting and measuring tools, technological equipment (for example, a three-jaw self-centering or four-jaw non-self-centering chuck, a drilling chuck, a rigid or rotating center, a fixed or movable steady rest, a collet chuck with a set of collets, etc.) in the tool room pantry;

4. time for the delivery of the required blanks to the workplace (with non-centralized delivery of blanks);

5. time to install the required devices on the machine and align them;

6. time to install the required cutting tools on the machine, adjust to the required dimensions when processing two to three test parts (when processing a batch of parts);

7. time for the delivery of processed parts;

8. time for cleaning the machine from chips;

9. time to remove attachments and cutting tools from the machine (if not used in the next work shift);

10. time to check in fixtures, cutting and measuring tools (which will not be used on the next work shift) in the tool pantry.

Typically, the preparatory and final time is from 10 to 40 minutes, depending on the accuracy and complexity of processing, the complexity of aligning fixtures and adjusting to dimensions.

2. For the area of ​​the workshop: The larger the batch, the more storage space is required.

3. On product cost through unfinished production: the larger the batch, the larger the work in progress, the higher the cost of production. The greater the cost of materials and semi-finished products, the greater the impact of work in progress on the cost of production.

The batch size of parts is calculated by the formula

n = N´ f/F , (8.2)

where n– batch size of parts, pcs.; N- the annual program for the manufacture of all parts of all groups, pieces; F- the number of working days in a year; f- the number of days of stock to store parts before assembly.

In this way, N/F– daily release program, pcs. Number of days of stock to hold parts before assembly f= 2…12. The larger the size of the part (more space required for storage), the more expensive the material and manufacturing (more money required, more to give back on loans), the less the number of days of stock to store parts before assembly is set ( f= 2..5). On practice f= 0.5…60 days.

In-line production is characterized by a start-up cycle and an exhaust cycle.

t h =F d m/N zap, (8.3)

where t h - start cycle, F d m- the actual fund of equipment time for the corresponding shift work m, N zap - a program for launching blanks.

The release cycle is defined in the same way.

t in =F d m/N vyp, (8.4)

where N issue - program for the release of parts.

Due to the inevitable appearance of defects (between 0.05% and 3%), the launch program should be larger than the release program by an appropriate proportion.

Production is called in-line, in which, in the steady state, all operations are simultaneously performed on an orderly moving set of similar products, except perhaps for a small number of them with incompletely loaded jobs.

In-line production in its most perfect form has a set of properties that correspond to the maximum extent to the principles of rational organization of production. These main properties are as follows.

Strict rhythmic production of products. Rhythm release- is the number of products produced per unit of time. Rhythm is the production of products with a constant rhythm over time.

Release stroke- This is the period of time after which the release of one or the same number of products of a certain type is periodically produced.

There are options for in-line production, in which, in principle, there is no rhythmic release at the level of individual items. Strict regularity of repetition of all flow operations - this property consists in the fact that all operations of mass production of a certain type of products are repeated at strictly fixed intervals, creating the prerequisites for the rhythmic release of these products.

Specialization of each workplace in the performance of one operation for the manufacture of products of a certain type.

Strict proportionality in the duration of the execution of all operations in-line production.

Strict continuity of the movement of each product through all operations of mass production.

Straightness of production. The location of all jobs in a strict sequence of technological operations in-line production. However, in a number of cases, for certain reasons, it is not possible to achieve complete straightness in the arrangement of workplaces, and returns and loops occur in the movement of products.

Types of production lines.

production line - This is a separate set of functionally interconnected workplaces, where the in-line production of products of one or several types is carried out.

According to the nomenclature of products assigned to submarines, there are:

One-subject submarines, each of which is specialized in the production of products of the same type

Multi-subject submarines, on each of which products of several types are simultaneously or sequentially manufactured, similar in design or technology for their processing or assembly.

According to the nature of the passage of products through all operations of the production process, there are:

Continuous production lines, on which the products are continuous, i.e. without interoperative decubitions, go through all operations of their processing or assembly

Discontinuous production lines, which have interoperative beds, i.e. discontinuity in processing or assembly of products.

By the nature of the tact, they distinguish:

Production lines with a regulated cycle, in which the cycle is set forcibly with the help of conveyors, light or sound signaling.

Production lines with free tact, on which the performance of operations and the transfer of products from one operation to another can be performed with slight deviations from the established settlement cycle.

Depending on the order of processing on them, products of various types are divided into:

Multi-subject production lines with sequential-batch alternation of batches of products of various types, in which each type of product is exclusively processed for a certain period, and the processing of various types of products is carried out in successive alternating batches. On lines of this type, it is necessary to rationally organize the transition from the production of products of one type to the production of another:

at the same time, assembly of new types of products is stopped at all workplaces of the production line. The advantage is the absence of loss of working time, however, this requires the creation of a backlog of products of each type at each workplace, which are in the stage of readiness that corresponds to the operation performed at this workplace.

products of a new type are launched on the production line until the assembly of a batch of products of the previous type is completed, and the maximum of two possible cycles for the old and new types of products is set on the production line during the transition period. However, during the transitional period, downtime of workers is possible at those workplaces where products are assembled with a lower required tact than that currently set.

group production lines, which are characterized by simultaneous processing on the production line of batches of products of several types.

The main condition for the effectiveness of the production system is the rhythm of the shipment of products in accordance with the needs of the customer. In this context, the main measure of rhythm is the takt time (the ratio of available time to the customer's established need for products). In accordance with the cycle, the workpieces are sequentially moved from process to process, and the finished product (or batch) appears at the output. If there are no big difficulties with the calculation of the available time, then the situation is not unambiguous with the determination of the number of planned products.

In modern production conditions, it is extremely difficult to find a single-product enterprise that would produce only one product name. One way or another, we are dealing with the release of a range of products that can be either of the same type or completely different. And in this case, a simple recalculation of the number of products to determine the volume of production is not acceptable, since products of different types cannot be mixed and counted as part of the total.

In some cases, to facilitate the accounting and understanding of the overall dynamics of productivity, enterprises use certain qualitative indicators that are to some extent inherent in the products produced. So, for example, finished products can be taken into account in tons, square, cubic and linear meters, in liters, etc. At the same time, the release plan in this case is set in these indicators, which, on the one hand, allows you to set specific, digitized indicators, and, on the other hand, the connection between production and the need of the customer who wants to receive products according to the nomenclature by a certain date is lost. And often a paradoxical situation arises when the plan in tons, meters, liters is completed during the reporting period, and the customer has nothing to ship, since there are no necessary products.

In order to carry out accounting and planning in a single quantitative indicator, while not losing touch with the order nomenclature, it is advisable to use natural, conditionally natural or labor methods for measuring output.

The natural method, when output is calculated in units of output, is applicable in limited conditions for the production of one type of product. Therefore, in most cases, a conditionally natural method is used, the essence of which is to bring the entire variety of similar products to a certain conventional unit. The role of a quality indicator by which products will be correlated can be, for example, fat content for cheese, heat transfer for coal, etc. For industries where it is difficult to clearly identify a quality indicator for comparing and accounting for products, the labor intensity of manufacturing is used. The calculation of the volume of production by the labor intensity of manufacturing each type of product is called the labor method.

The combination of labor and conditionally natural methods of measuring the volume of production in accordance with a certain nomenclature most accurately reflects the needs of most industrial productions in accounting and planning.

Traditionally, a typical representative (the most massive) of manufactured products with the least labor intensity is chosen as a conventional unit. To calculate the conversion factor (k c.u. i) are related technologically to the complexity i th item of the nomenclature and the item that is accepted as conditional:

k c.u. i— coefficient of conversion to arbitrary units for i-th product;

Tr i— technological complexity i-th product, standard hour;

Tr c.u. - technological labor intensity of the product accepted as a conditional unit.

After each product has its own conversion factors into conventional units, it is necessary to determine the quantity for each of the positions of the nomenclature:

OP c.u. - the volume of production of conventional units, pieces;

- the sum of the products of the conversion coefficient in conventional units for i-th product and planned production volume i-th product;

n- the number of positions in the nomenclature.

To illustrate the methodology, consider an example in which it is necessary to manufacture three types of products (see Table 1). When converted into conventional units, the output plan will be 312.5 pieces of products A.

Table 1. Calculation example

Based on an understanding of the total volume of production in the planned period, it is already possible to calculate the takt time (the main indicator for synchronizing and organizing production flows) using the well-known formula:

BT c.u. - takt time for a conventional unit, minutes (seconds, hours, days);

OP c.u. - the volume of production of conventional units, pieces.

It should be noted that an indispensable condition for using the labor method is the validity of the norms used in the calculations, their compliance with the actual time spent. Unfortunately, in most cases this condition cannot be met for various reasons, both organizational and technical. Therefore, the use of the labor method can give a distorted picture of the dynamics of production volume.

However, the use of the labor method in the framework of calculating the conventional unit of measure of planned output does not have such a strict limitation. The use of even overestimated standard indicators, if the overestimation is of a systemic nature, in no way affects the results of calculations (see Table 2).

Table 2. Applicability of the method at overestimated rates

As can be seen from the above example, the final value of the output volume does not depend on the “quality” of the normative material used. In both cases, the volume of production in arbitrary units remains unchanged.

Calculation of available time for the selected item

In addition to the conditionally natural method, an approach is proposed to determine the available time for the selected range of manufactured products in the event that the calculation of the takt time is not performed for the entire production volume. In this case, there is a need to allocate from the total available time a share that will be used for the production of the selected product.

To calculate the total planned volume of production, the labor method of calculating labor productivity is used, both for the entire volume of production and for that nomenclature, the takt time of which is supposed to be set in the future:

OP tr - the volume of production in the labor dimension, norm-hour (man-hour);

Tr i- normative labor intensity i-th product, norm-hours (man-hours);

OP i- release plan i-th product;

k v.n. i- the coefficient of compliance with the norms.

It is important that in this case the coefficient of compliance with the norms is used in order to ensure that the calculated data correspond to the real production possibilities. This coefficient can be calculated both for each type of product, and for the entire volume of production.

DV i- time available for i-th product;

OP tr i- volume of production i-th product in the labor dimension, standard hour (man-hour);

DV - total available time, min. (hours, days).

For verification, the total available time is the sum of the calculated shares for each item, determined by the production plan:

Table 3. Example of calculating available time

OD 1 = 100 × 2.5 × 1.1 + 150 × 2 × 1.1 + 200 × 1.5 × 1.1 = 935 standard hours

OP 2 = 75 × 3 × 1.1 + 125 × 2.2 × 1.1 = 548 standard hours

hour.

hour.

As a result, we calculate the takt time for Nomenclature 1, as a conditional unit we take Product 1.3.:

PCS.

These approaches to the calculation of the main production indicators make it possible to quickly and close to reality make the main calculations to determine the target takt time. And in cases where there is an extensive range of typical products, these methods make it possible to balance and synchronize production based on existing data on the cycle time of each process and the takt time set by consumer demand.

In mechanical engineering, there are three types of industries: mass, serial and single and two working methods: flow and non-flow.

Mass production characterized by a narrow range and a large volume of products produced continuously for a long time. The main feature of mass production is not only the number of products produced, but also the execution of one constantly recurring operation assigned to them at most workplaces.

The release program in mass production makes it possible to narrowly specialize workplaces and locate equipment along the technological process in the form of production lines. The duration of operations at all workplaces is the same or a multiple of time and corresponds to the specified performance.

The release cycle is the time interval through which the release of products is periodically produced. It significantly affects the construction of the technological process, since it is necessary to bring the time of each operation to a time equal to or a multiple of a cycle, which is achieved by appropriately dividing the technological process into operations or duplicating equipment to obtain the required performance.

In order to avoid interruptions in the work of the production line at the workplace, inter-operational stocks (reserves) of blanks or parts are provided. Backlogs ensure the continuity of production in the event of an unforeseen stoppage of individual equipment.

The in-line organization of production provides a significant reduction in the technological cycle, interoperational backlogs and work in progress, the possibility of using high-performance equipment and a sharp decrease in the labor intensity and cost of products, ease of planning and production management, and the possibility of complex automation of production processes. With flow methods of work, working capital is reduced and the turnover of funds invested in production is significantly increased.

Mass production It is characterized by a limited range of products manufactured in periodically repeated batches and a large output.

In large-scale production, special-purpose equipment and modular machines are widely used. The equipment is located not according to the types of machine tools, but according to the manufactured items and, in some cases, in accordance with the technological process being performed.

Medium series production occupies an intermediate position between large-scale and small-scale production. The batch size in mass production is affected by the annual production of products, the duration of the processing process and the adjustment of technological equipment. In small-scale production, the batch size is usually several units, in medium-scale production - several tens, in large-scale production - several hundred parts. In electrical engineering and apparatus building, the word "series" has two meanings that should be distinguished: a number of machines of increasing power of the same purpose and the number of machines or devices of the same type simultaneously launched into production. Small-scale production in its technological features is approaching a single one.

Single production characterized by a wide range of manufactured products and a small volume of their output. A characteristic feature of unit production is the implementation of various operations at the workplace. Single-piece production - machines and devices that are manufactured according to individual orders, providing for the fulfillment of special requirements. They also include prototypes.

In unit production, electrical machines and devices of a wide range are produced in relatively small quantities and often in a single copy, so it must be universal and flexible to perform various tasks. In single production, quick-change equipment is used, which allows you to switch from the manufacture of one product to another with minimal loss of time. Such equipment includes machine tools with program control, computer-controlled automated warehouses, flexible automated cells, sections, etc.

Universal equipment in single production is used only at enterprises built earlier.

Some technological methods that have arisen in mass production are used not only in mass production, but also in single production. This is facilitated by the unification and standardization of products, the specialization of production.

The assembly of electrical machines and apparatus is the final technological process in which individual parts and assembly units are combined into a finished product. The main organizational forms of assembly are stationary and mobile.

For stationary assembly the product is completely assembled at one workplace. All parts and assemblies required for assembly are delivered to the workplace. This assembly is used in single and serial production and is performed in a concentrated or differentiated way. With the concentrated method, the assembly process is not divided into operations and the entire assembly (from beginning to end) is performed by a worker or a team, and with a differentiated method, the assembly process is divided into operations, each of which is performed by a worker or a team.

With mobile assembly the product is moved from one workplace to another. Workplaces are equipped with the necessary assembly tools and fixtures; on each of them, one operation is performed. The movable form of assembly is used in large-scale and mass production and is carried out only in a differentiated way. This form of assembly is more progressive, since it allows assemblers to specialize in certain operations, resulting in increased labor productivity.

During the production process, the assembly object must sequentially move from one workplace to another along the stream (such movement of the assembled product is usually carried out by conveyors). The continuity of the process during in-line assembly is achieved due to the equality or multiplicity of the execution time of operations at all workplaces of the assembly line, i.e., the duration of any assembly operation on the assembly line must be equal to or a multiple of the release cycle.

The assembly cycle on the conveyor is the planning beginning for organizing the work of not only the assembly, but also all the procurement and auxiliary workshops of the plant.

With a wide range and small quantities of manufactured products frequent reconfiguration of equipment is required, which reduces its performance. In order to reduce the labor intensity of manufactured products, in recent years, flexible automated production systems (GAPS) have been developed on the basis of automated equipment and electronics, which make it possible to manufacture individual parts and products of various designs without reconfiguring equipment. The number of products manufactured at the GAPS is set during its development.

Depending on the designs and overall dimensions of electrical machines and apparatuses, various technological assembly processes . The choice of the assembly process, the sequence of operations and equipment is determined by the design, output volume and degree of their unification, as well as the specific conditions available at the plant.

Release cycle calculation. Determining the type of production. Characteristics of a given type of production

The dependence of the type of production on the volume of production of parts is shown in Table 1.1.

With a part weight of 1.5 kg and N=10,000 parts, medium-scale production is selected.

Table 1.1 - Characteristics of the type of production

Serial production is characterized by a limited range of manufactured parts manufactured in periodically repeating batches and a relatively small volume of output than in single production.

The main technological features of mass production:

1. Assigning several operations to each workplace;

2. The use of universal equipment, special machines for individual operations;

3. Arrangement of equipment by technological process, type of part or groups of machines.

4. Wide application of spec. Fixtures and tools.

5. Compliance with the principle of interchangeability.

6. Average qualification of workers.

The value of the release cycle is calculated by the formula:

where F d - the actual annual fund of the operating time of the equipment, h / cm;

N - annual program for the production of parts, N=10,000 pcs

Next, you need to determine the actual fund of time. When determining the fund of operating time of equipment and workers, the following initial data for 2014 were adopted at a 40-hour working week, Fd = 1962 h / cm.

Then by formula (1.1)

The type of production depends on two factors, namely: on a given program and on the complexity of manufacturing a product. On the basis of a given program, the cycle of product release t B is calculated, and the labor intensity is determined by the average piece (piece-calculation) time T pcs for the operations of an existing production or similar technological process.

In mass production, the number of parts in a batch is determined by the following formula:

where a is the number of days for which it is necessary to have a stock of parts, for = 1;

F - number of working days in a year, F=253 days.

Analysis of the requirements for the accuracy and roughness of the machined surfaces of the part and a description of the accepted methods for ensuring them

The part "Intermediate shaft" has low requirements for the accuracy and roughness of the machined surfaces. Many surfaces are machined to the fourteenth grade of accuracy.

The part is technological, because:

1. Free tool access is provided to all surfaces.

2. The part has a small number of precise dimensions.

3. The workpiece is as close as possible to the shape and dimensions of the finished part.

4. The use of high-performance processing modes is allowed.

5. There are no very exact sizes, except: 6P9, 35k6, 30k6, 25k6, 20k6.

The part can be obtained by stamping, so the configuration of the outer contour does not cause difficulties in obtaining the workpiece.

In terms of machining, the part can be described as follows. The design of the part allows its processing for a pass, nothing interferes with this type of processing. There is free access of the tool to the processed surfaces. The part provides for the possibility of processing on CNC machines, as well as on universal machines, it does not present difficulties in basing, which is due to the presence of planes and cylindrical surfaces.

It is concluded that, from the point of view of the accuracy and cleanliness of the machined surfaces, this part generally does not present significant technological difficulties.

Also, to determine the manufacturability of a part,

1. Accuracy factor, CT

where K PM - accuracy factor;

T SR - the average quality of the accuracy of the surfaces of the part.

where T i - quality of accuracy;

n i - the number of surfaces of the part with a given quality (table 1.2)

Table 1.2 - The number of surfaces of the part "Intermediate shaft" with a given quality

In this way

2. Coefficient of roughness, KSh

where K W - roughness coefficient,

Ra SR - average roughness.

where Ra i is the surface roughness parameter of the part;

m i - the number of surfaces of the part with the same roughness parameter (table 1.3).

Table 1.3 - The number of surfaces of the part "Intermediate shaft" with a given roughness class

In this way

The coefficients are compared with one. The closer the values ​​of the coefficients are to one, the more manufacturable the part is. From the above, we can conclude that the part is quite technologically advanced.