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 narrow specialization workplaces and location of 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 reduction in the labor intensity and cost of products, ease of planning and production management, the possibility integrated automation production processes. With in-line methods of work, they decrease revolving funds and significantly increases the turnover of funds invested in production.
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 aggregate 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 influenced by the annual production of products, the duration of the processing and setup process. 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.
Assembly electrical machines and apparatus - 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 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 systems have been developed on the basis of automated equipment and electronics. production systems(GAPS), allowing to manufacture individual parts and products of various designs without reconfiguring the 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
|
details, kg |
Type of production |
||||
|
single |
Small-scale |
Medium series |
large-scale |
Mass |
|
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.
Main technological features batch 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 were adopted for 2014 with 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 it to be processed for a pass, nothing interferes this species 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.
Production type:
The volume of output - the number of products of certain names and sizes, manufactured or repaired by the enterprise during the planned time interval.
Release program - a list of products manufactured at the enterprise, indicating the volume of output for each item during the calendar period.
The product release cycle is understood as the time interval between the release of two successive machines, parts or blanks.
That is, the release cycle is the length of time required to manufacture one part with 100% completion of the release program. When designing technological processes, the value of the release cycle is determined by the formula:
The actual annual fund of equipment operation, hour;
m is the number of work shifts;
N is the annual product release program, pcs.
Coefficient definition.
The serialization coefficient shows the number of different operations assigned to one machine and is calculated by the formula:
Tact of production of products, min;
Piece time for operations, min.
The criterion for serialization is the coefficient of consolidation of operations () - the ratio of the number of all technological operations performed or to be performed within a month to the number of jobs.
There are three main types of production: single, serial and mass. Values = 21-40 are typical for small-scale production, 11-20 for medium-scale production, and 2-10 for large-scale production.
Single production is characterized by a small volume of production of identical products, the re-production of which, as a rule, is not provided.
It is this kind of production that is typical for technical service enterprises, repair shops and mechanical repair shops of timber industry enterprises.
Serial production is characterized by a limited range of products manufactured or repaired in periodically repeated batches and a relatively small output. Depending on the number of products in a batch or series, small-batch, medium-batch or large-batch production is distinguished.
Mass production is characterized by a large volume of products produced continuously for a long time. Most workplaces perform one constantly repetitive operation (=1).
Comparative technical and economic characteristics of production types are presented in Table. four.
Table 4. - Comparative technical and economic characteristics of production types:
|
Production types |
|||
|
unit |
serial |
mass |
|
|
Product range |
Unlimited |
limited series |
One name |
|
Nomenclature constancy |
Doesn't repeat |
Repeats periodically |
Constant release of products of a narrow range |
|
Job specialization |
Missing. Miscellaneous operations |
Periodically recurring operations |
One repetitive operation |
|
Operations pinning coefficient () |
Small-scale 20…40 |
Medium series 10.. 20 Large series 1…10 |
|
|
Equipment |
Universal |
Universal, CNC, Specialized |
Mainly special |
|
Location of production (technological) equipment |
Technological principle (by groups of machines) |
Subject and technological principle (by groups, by sections, by technological process) |
Subject principle on the technological process |
|
Technological equipment (devices, cutting and measuring tools, etc.) |
Universal, standard normalized and unified. |
Standard, normalized and specialized. Versatile and ultimate. |
Special and normalized. Ultimate and Special |
|
Development detail technological documentation |
Route |
Route operating room |
Detailed route-operational up to the development of individual techniques |
|
Qualification of key workers |
Medium, high on CNC machines |
Low on production lines, high on GAL |
|
|
Product cost |
|||
|
The production cycle |
Long |
Minimum |
|
|
Labor productivity |
low |
Maximum |
|
|
Labor rationing |
Experimental-statistical |
Estimated and experimental-statistical |
Estimated with experimental verification |
The type of production has a decisive influence on the efficiency of the use of enterprise resources.
Pilot production belongs to an independent type. Its purpose is to produce samples, batches or series of products for research work, testing, fine-tuning the design and, on the basis of this, the development of design and technological documentation for industrial production. Pilot production products are not commercial products and usually do not go into operation.
Engineering technology- a science that studies and establishes the patterns of the flow of processing processes and parameters, the impact on which most effectively affects the intensification of processing processes and increase their accuracy. The subject of study in engineering technology is the manufacture of products of a given quality in the quantity established by the production program, at the lowest cost of materials and the minimum cost.
Detail- this is an integral part of the product, made of a homogeneous material without the use of assembly operations. characteristic feature details - the absence of detachable and one-piece connections in it. A part is the primary assembly element of every machine.
assembly unit is a product made up of constituent parts collected separately from other elements of the product. As part of assembly unit both individual parts and components of lower orders can act.
Manufacturing process is a set of interrelated actions, as a result of which raw materials and semi-finished products are converted into finished products. In concept manufacturing process includes:
In engineering, there are three type of production: massive, serial and singular.
AT mass production, products are manufactured continuously, in large quantities and for a long time (up to several years). AT serial- batches (series) of products that are regularly repeated at certain intervals. AT single- products are made in small quantities and, often, individually.
criterion, which determines the type of production, is not the number of manufactured products, but the assignment to the workplace of one or more technological operations (the so-called. coefficient of fixing technological operations k ).
This is the ratio of the number of all technological operations performed or to be performed to the number of jobs.
So, for mass production, it is characteristic that most jobs are assigned only one constantly recurring operation, for serial production - several periodically repetitive operations, for a single one - a wide variety of non-repeating operations.
Another distinguishing feature of production types is the release cycle.
, - the time interval through which the release of products is periodically produced.The release cycle is determined by the formula:
where F E- annual, efficient fund time of the workplace, section or workshop, h
P- annual production program for the release of a workplace, section or workshop, pcs.
AT- the number of days off in a year;
P p - quantity public holidays per year;
t p days - the duration of the working day, hour;
n cm - the number of shifts.
Manufacturing program factory- this is the annual number of manufactured products expressed in labor intensity:
where P 1 ,P 2 and P n- production programs for products, man-hour.
Production program of the shipyard (SRZ)
| Labor intensity of work by quarters, person · hour. | |||||
| Name | I | II | III | IV | TOTAL: |
| Ship repair: | |||||
| - navigational | XXX | XXX | XXX | XXX | P 1 |
| - current | XXX | XXX | XXX | XXX | P 2 |
| - average | XXX | XXX | XXX | XXX | P 3 |
| - capital | XXX | XXX | XXX | XXX | ... |
| Shipbuilding | XXX | XXX | XXX | XXX | ... |
| mechanical engineering | XXX | XXX | XXX | XXX | ... |
| Other works | XXX | XXX | XXX | XXX | P n |
| TOTAL: | XXXX | XXXX | XXXX | XXXX | 320000 |
NOTE: The symbol XXXX or XXXX in the table refers to any number of man-hours. Nomenclature - the annual number of manufactured products, expressed in items.
Shipyard nomenclature
| Name | Quantity, pcs. |
| Ship repair: | |
| Passenger ship (PT) pr. 544 | 4 |
| PT pr. R - 51 | 8 |
| Cargo-passenger ship (GPT) pr. 305 | 2 |
| Dredger pr. 324 A | 4 |
| Towing ship (BT) pr. 911 V | 8 |
| ................... | ............ |
| Shipbuilding: | |
| barge project 942 A | 5 |
| barge pr. R - 14 A | 4 |
| BT pr. 1741 A | 1 |
| Engineering: | |
| winch LRS - 500 | 25 |
| etc. | ... |
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