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 a 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 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 product release cycle 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. To all surfaces is provided Free access tool.
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.
Mass-flow creation is characterized by the fact that parts after processing on one machine or workplace are immediately transferred for processing to another workplace during the technological process. The movement of parts is carried out using the assembly flow, trolleys, hoists, etc. In mass production, operations are synchronized, i.e. the time for each operation is taken equal to or a multiple of the cycle.
The organization of in-line production is associated with a number of calculations and preliminary work. Starting moment when designing in-line production is to determine the volume of output and cycle.
Tact - this is the time gap between the launch (or release) of 2 adjacent products on the strip. It is determined by the following formula (see formula 1 in the text).
The reciprocal of a beat is called pace strip work. When organizing in-line production, it is necessary to ensure such a pace in order to fulfill the production plan. Rhythm determines the number of parts produced per unit of time (see formula 2 in the text).
The general once-through creation is also characterized by the arrangement of equipment in the order of the sequence of the technological process. But unlike mass production, the time of individual operations is not synchronized with each other, i.e. does not always equal tact. As a result, at workplaces with a long duration of operations, stocks of parts are sometimes created and their movement from machine to machine is irregular. Therefore, they strive to have mass production as a more perfect form of production.
What is a production cycle and how is it determined?
Flow-mass creation is characterized by the fact that parts after processing on one machine or workplace are immediately transferred for processing to another workplace in the course of the technological process. The movement of parts is carried out using the assembly flow, trolleys, hoists, etc. In mass production, operations are synchronized, i.e. the time for each operation is taken equal to or a multiple of the cycle. Organization of flow...
Production characteristic
Working hours and time funds
The mode of operation includes the number of working days per year, excluding weekends and holidays, with two shifts per day, because. an automated section is being developed. The full calendar annual fund of time shows the number of hours in a year 24363=8670h.
Excluding weekends and holidays, based on a five-day working week lasting 41 hours, we get the nominal fund of time FN = 4320 hours.
We take into account equipment downtime for repairs, FD - the actual annual fund of equipment operation time for 2-shift operation.
PD = 3894 hours.
Determination of the release cycle
To justify the organization production process and determining the type of production, it is necessary to calculate the average production rate - and the average piece time - Tsh.sr. production of the product in the main operations.
The release cycle is determined by the formula:
(min/pcs) (3.3.1)
where Fd = 3894 hours;
Ng = 20000pcs - annual program for the production of parts;
fs = 3894 60/20000 = 11.7 min/pc
Determining the type of production
The type of production can be determined by the numerical value of the operation fixing coefficient, the calculation of which is carried out in accordance with GOST 3.11.08-74. Approximately the type of production can be determined by the value of the coefficient - Kc
where Tsht.sr - the average piece time of manufacturing the product, is determined according to the data of the current technical process.
Tsht.av. = 71.43/17 = 4.2 min.
Kzo \u003d 11.6 / 4.2 \u003d 2.7
1< Кс?10 - крупносерийное производство
Analysis of the manufacturability of the design of the part "Drive shaft"
Manufacturability - a property of the product, according to which the design of the part must comply with the use of the most advanced processing or assembly methods in the manufacture.
Rational designs of machines that provide the necessary operational requirements cannot be created without taking into account the labor intensity and material consumption of their manufacture. Compliance of the design of machines with the requirements of labor intensity and material consumption determines the manufacturability of the design. In an objective assessment of the manufacturability of the design of machines, their parts and assemblies, a number of positive factors are taken into account that determine the manufacturability of the design.
In an objective assessment of the manufacturability of the design of machines, their parts and assemblies, a number of positive factors are taken into account that determine the manufacturability of the design. These include:
The optimal shape of the part, which ensures the manufacture of the workpiece with the smallest allowance and the smallest number of machined surfaces;
The smallest weight of the machine;
The smallest amount of material used in the construction of machines;
Interchangeability of parts and assemblies with the optimal value of tolerance fields;
Normalization (standardization) and unification of parts, assemblies and their individual design elements.
The basic requirements for the manufacturability of the design of machine building parts are set out in the literature.
Part designs must consist of standard and unified structural elements (QED) or be standard as a whole. Parts must be made from standard or unified blanks. The dimensions of the part must have optimal accuracy. Surface roughness must be optimal. Physico-chemical and mechanical properties the material of the part, its rigidity, shape, dimensions must comply with the requirements of the manufacturing technology (including the processes of finishing and hardening treatment, applying anti-corrosion coatings, etc.), as well as storage and transportation.
The base surface of the part must have optimal indicators of accuracy and surface roughness, which provide the required accuracy of installation, processing and control.
Blanks for the manufacture of parts must be obtained in a rational way, taking into account the material, the given output volume and the type of production. The method of manufacturing parts should allow the simultaneous production of several parts. The design of the part must ensure the possibility of using typical and standard technological processes its manufacture.
We will test the manufacturability of the “Drive shaft” part for manufacturability in accordance with Guidelines.
Production type:
Output volume - 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 various 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, remanufacturing which are usually 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 |
|
Detailing the development of 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.
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 processed exclusively 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.
