Product release cycle. What is a production cycle and how is it determined? Terms and definitions of basic concepts of technological preparation of production
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 during the technological process. The parts are moved using an assembly flow, trolleys, hoists, etc. In mass flow production, operations are synchronized, i.e. The time for each operation is taken equal to or a multiple of the cycle.
The organization of continuous production is associated with a number of calculations and preliminary work. The initial point in designing a continuous production process is to determine the volume of production and cycle time.
Tact - This is the time gap between the launch (or release) of two adjacent products onto the strip. It is determined by the following formula (see formula 1 in the text).
The value reciprocal to the beat is called pace strip work. When organizing continuous 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).
General direct-flow generation is also characterized by the arrangement of equipment in the sequence of the technological process. But unlike mass production, the time of individual operations is not synchronized with each other, i.e. not always equal to beat. As a result, at workplaces with a long duration of operations, stocks of parts are sometimes created and their movement from machine to machine occurs irregularly. Therefore, they strive to have mass production as a more advanced 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 during the technological process. The parts are moved using an assembly flow, trolleys, hoists, etc. In mass flow production, operations are synchronized, i.e. The time for each operation is taken equal to or a multiple of the cycle. Organization of in-line...
The main condition for the efficiency of the production system is the rhythm of shipment of products in accordance with customer needs. In this context, the main measure of rhythm is takt time (the ratio of available time to the customer’s established need for products). In accordance with the cycle, workpieces are sequentially moved from process to process, and the finished product (or batch) appears at the output. If there are no major difficulties in calculating the available time, then the situation with determining the number of planned products is not clear.
In modern production conditions, it is extremely difficult to find a mono-product enterprise that would produce only one type of product. One way or another, we are dealing with the release of any range of products, which can be either 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 taken into account within the total quantity.
In some cases, to facilitate accounting and understanding of the overall dynamics of productivity, enterprises use certain quality indicators that are, to one degree or another, inherent in the products they produce. So, for example, finished products can be counted in tons, square, cubic and linear meters, in liters, etc. Moreover, the production 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 needs 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 fulfilled during the reporting period, but 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, without losing touch with the order nomenclature, it is advisable to use natural, conditionally natural or labor methods of measuring output volume.
The natural method, when output is calculated in units of manufactured products, is applicable in limited production conditions of one type of product. Therefore, in most cases, a conditionally natural method is used, the essence of which is to reduce the entire variety of similar products to a certain conventional unit. The role of a qualitative 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 unambiguously identify a qualitative indicator for comparing and accounting for products, the labor intensity of production is used. Calculation of production volume based on the labor intensity of manufacturing each type of product is called the labor method.
The combination of labor and conditionally natural methods of measuring production volume in accordance with a certain nomenclature most accurately reflects the needs of the majority industrial production in accounting and planning.
Traditionally, a typical representative (the most massive) of manufactured products with the least labor intensity is selected as a conventional unit. To calculate the conversion factor (k c.u. i) are technologically related to labor intensity i th product of the nomenclature and the product that is accepted as conditional:
k c.u. i— conversion factor into conventional units for i-th product;
Tr i— technological complexity i-th product, standard hour;
Tr.e. — technological complexity of the product accepted as a conventional unit.
After each product has its own conversion factors into conventional units, it is necessary to determine the quantity for each item in the nomenclature:
OP u.e. — volume of production of conventional units, pieces;
— the sum of the products of the conversion factor into conventional units for i-th product and planned production volume i-th product;
n— number of items in the nomenclature.
To illustrate the methodology, consider an example in which it is necessary to produce three types of products (see Table 1). When converted into conventional units, the production plan will be 312.5 units of products A.
Table 1. Calculation example
|
Product |
Quantity, pcs. |
Labor intensity, standard hour |
Quantity of cu, pcs. |
|
Based on an understanding of the total volume of production in the planning period, it is already possible to calculate takt time (the main indicator for synchronizing and organizing production flows) using the well-known formula:
VT.e. - takt time for a conventional unit, minutes (seconds, hours, days);
OP u.e. — production volume of conventional units, pieces.
It should be noted that an indispensable condition for using the labor method is the validity of the standards used in the calculations and 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 may give a distorted picture of the dynamics of production volume.
However, the use of the labor method within the framework of calculating a conventional unit of measurement of planned output does not have such a strict limitation. The use of even overestimated standard indicators, if the overestimation is systemic in nature, does not in any way affect the results of calculations (see Table 2).
Table 2. Applicability of the method at excessive rates
|
Quantity, pcs. |
Labor is standard, standard hour |
k c.u. i |
Quantity of units, pcs. |
Actual labor, standard hour |
k c.u. i |
Quantity of units, pcs. |
|
As can be seen from the above example, the final value of the output volume does not depend on the “quality” of the standard material used. In both cases, the volume of production in conventional units remains unchanged.
Calculation of available time for the selected item
In addition to the conditionally natural method, an approach is proposed for determining the available time for a selected range of manufactured products in the event that the takt time is not calculated for the entire production volume. In this case, there is a need to allocate a portion of the total available time that will be used to produce the selected product.
To calculate the total planned production volume, the labor method of calculating labor productivity is used, both for the entire production volume and for the item whose takt time is subsequently expected to be established:
OP tr - production volume in labor terms, standard hour (man-hour);
Tr i- standard labor intensity i th product, standard hours (man-hours);
OP i— release plan i-th product;
k v.n. i- coefficient of compliance with standards.
It is important that in this case the coefficient of compliance with standards is used in order to ensure compliance with the calculated data real possibilities production. This coefficient can be calculated both for each type of product and for the entire production volume.
Far East i- available time 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 consists of the calculated shares for each item determined by the production plan:
Table 3. Example of calculating available time
|
Product |
Release plan, pcs. |
Labor, standard hour |
Compliance coefficient |
Release plan, standard hour |
Available time |
|
Nomenclature 1 | |||||
|
Product 1.1. | |||||
|
Product 1.2. | |||||
|
Product 1.3. | |||||
|
Nomenclature 2 | |||||
|
Product 2.1. | |||||
|
Product 2.2. | |||||
|
1483 |
1500 |
OP 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 will calculate the takt time for Nomenclature 1, taking Product 1.3 as a conventional unit:
PC.
These approaches to calculating the main production indicators make it possible to make basic calculations to determine the target takt time quite quickly and close to reality. And in cases where there is an extensive range of standard 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 established by consumer demand.
Mechanical Engineering Technology- a science that studies and establishes the patterns of processing processes and parameters, the influence of which most effectively affects the intensification of processing processes and increasing their accuracy. The subject of study in mechanical engineering technology is the production of products of a given quality in the quantity established by the production program, with the lowest cost of materials and minimum cost.
Detail- this is a component of a product made from a homogeneous material without the use of assembly operations. A characteristic feature of the part is the absence of detachable and permanent connections in it. A part is the primary assembly element of each machine.
Assembly unit- this is a product connected from component parts assembled separately from the other elements of the product. Both individual parts and components of lower orders can act as components of an assembly unit.
Manufacturing process is a set of interrelated actions, as a result of which raw materials and semi-finished products are transformed into finished products. In concept manufacturing process includes:
In mechanical engineering there are three type of production: massive, serial And single.
IN massive In production, products are manufactured continuously, in large quantities and over a long period of time (up to several years). IN serial- batches (series) of products that are regularly repeated at certain intervals. IN single- products are made in small quantities and, often, individually.
criterion, which determines the type of production, is not the number of products produced, but the assignment of one or more technological operations to a workplace (the so-called technological operations consolidation coefficient k z ).
This is the ratio of the number of all technological operations performed or to be performed to the number of jobs.
Thus, mass production is characterized by assigning to most jobs only one constantly repeating operation, serial production is characterized by several periodically repeating operations, and individual production is characterized by a wide variety of non-repeating operations.
To others hallmark types of production is the release cycle.
, - the time interval through which products are periodically produced.The release stroke is determined by the formula:
Where F E- annual, effective time fund of a workplace, site or workshop, h
P- annual production program for the production of a workplace, site or workshop, pcs.
IN- number of days off per year;
P p - number of holidays per year;
t r day - duration of the working day, hour;
n cm - number of shifts.
Manufacturing program plant- this is the annual number of products produced expressed in labor intensity:
where P 1 ,P 2 And P n- production programs for products, person hour.
Production program of the ship repair plant (SRZ)
| Labor intensity of work by quarter, person hour. | |||||
| Name | I | II | III | IV | TOTAL: |
| Ship repair: | |||||
| - navigation | 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: XXX or XXXX in the table refers to any number of man-hours. Nomenclature - the annual number of products produced, expressed in names.
Nomenclature of SRZ
| Name | Quantity, pcs. |
| Ship repair: | |
| Passenger motor ship (PT) pr. 544 | 4 |
| PT Ave. R - 51 | 8 |
| Cargo-passenger motor ship (GPT) pr. 305 | 2 |
| Dredger pr. 324 A | 4 |
| Tugboat (BT) pr. 911 V | 8 |
| ................... | ............ |
| Shipbuilding: | |
| barge pr. 942 A | 5 |
| barge pr. R - 14 A | 4 |
| BT pr. 1741 A | 1 |
| Mechanical engineering: | |
| winch LRS - 500 | 25 |
| etc. | ... |
Takt time is one of the key principles of lean manufacturing. Takt time sets the speed of production, which must exactly match the existing demand. Takt time in production is similar to the human heart rate. Takt time is one of the three elements of a just-in-time system (along with in-line production and the pull system) that ensures work is evenly loaded and identifies bottlenecks. To design manufacturing cells, assembly lines, and create lean manufacturing, an absolute understanding of takt time is essential. This article discusses situations in which an artificial increase or decrease in takt time is possible.
What is takt time? The word tact comes from the German takt, which means rhythm or beat. The term beat time is related to musical terminology and refers to the rhythm that the conductor sets so that the orchestra plays in unison. In a lean production system, this concept is used to ensure the rate of production with the average rate of change in the level of consumer demand. Takt time is not a numerical indicator that can be measured, for example, using a stopwatch. The concept of takt time must be distinguished from the concept of cycle time (the time it takes to complete one operating cycle). The cycle time can be less than, greater than, or equal to the takt time. When the cycle time of each operation in a process becomes exactly equal to the takt time, one-piece flow occurs.
There is the following formula for calculation:
Takt time = available production time(per day) / consumer demand (per day).
Takt time is expressed in seconds per product, indicating that consumers purchase products once every certain period of time in seconds. It is incorrect to express takt time in units per second. By setting the pace of production in accordance with the rate of change in consumer demand, lean manufacturers thereby ensure that work is completed on time and reduces waste and costs.
Reduced takt time. The purpose of determining takt time is to work according to customer demand. But what happens if takt time is artificially reduced? The work will be completed faster than required, resulting in overproduction and excess inventory. If other tasks are unavailable, workers will waste time waiting. In what situation is such an action justified?
To demonstrate a similar situation, let’s calculate the required number of workers on an assembly line on which the flow of single products is carried out:
Group size = sum of manual cycle times / takt time.
Thus, if the total cycle time for a process is 1293 s, then the group size will be 3.74 people (1293 s / 345 s).
Since it is impossible to employ 0.74 people, the number 3.74 must be rounded. Three people may not be enough to keep production pace in line with changing consumer demand. In this case, improvement activities must be carried out to reduce the cycle time of manual operations and eliminate waste in the process.
If the cycle time is fixed, then it is possible to round up by reducing the takt time. Takt time can be reduced if available production time decreases:
3.74 people = 1293 s per product / (7.5 hours x 60 min x 60 s / 78 parts);
4 people = 1293 s / (7 hours x 60 min x 60 s / 78 parts).
By employing four people, reducing takt time and producing the same volume in less time, the team's workload is evenly distributed. If these four people can keep production up to speed with customer demand in less time than usual, they will need to be rotated or assigned to process improvement issues.
Increasing takt time: 50 second rule. In the example above, we show when takt time can be reduced to improve efficiency. Let us now consider the case where the takt time should be increased.
A rule of thumb is that all repetitive manual operations should have a cycle time of at least 50 seconds (start to start time). For example, the operation of company assembly lines Toyota determined by the takt time 50 60 s. If the company needs to increase production volume by 5-15%, then introduce Extra time or in some cases using multiple assembly lines configured for longer takt times (for example, two lines with a takt time of 90 s instead of one line with a takt time of 45 s).
There are four reasons why the 50 second rule is important.
- Performance. If the takt time is small, then even seconds spent as a result of unnecessary movements result in large losses of cycle time. Losing 3 s out of 30 s cycle time results in a 10% reduction in productivity. Losing 3 seconds out of a 60 second cycle results in a 5% reduction in performance. Losing 3 s out of a 300 s cycle to only 1%, etc. Therefore, if the takt time is a larger value (50 s or more), then this will not be a significant loss in productivity.
Using one assembly line with a large number of operators working in a short takt time (eg 14 s) saves on investment costs (number of lines), but will result in higher operating costs. We have found that assembly lines designed to operate at speeds of 50 seconds or more are 30% more productive than lines with low takt times. - Safety and ergonomics. Performing the same manual tasks for a short period of time can lead to fatigue and muscle pain due to repetitive strain. When various operations are performed over a longer period of time (for example, in 60 seconds instead of 14 seconds), the muscles have time to recover before starting the operation again.
- Quality. By performing a wide range of responsibilities (for example, five operations instead of two), each employee himself becomes an internal consumer of every operation except the last one. If a worker performs five operations, it forces him to pay more attention to quality, since an unsatisfactory result in operation 3 will be reflected in the performance of operation 4 and, therefore, will not be passed on unnoticed to the next stage.
- Attitude to the work performed. It has been noted that workers experience greater job satisfaction when performing a task repeatedly, For example every 54 s, not 27 s. People enjoy learning new skills, they experience less fatigue when performing repetitive movements, but most importantly, employees feel that they are making a personal contribution to the creation of the product, and are not just doing mechanical work.
Takt time and investment. The importance of the 50 second rule can be illustrated by the example of a company engaged in the production and assembly of pumps for industry. The company used one long assembly line to create its product. As a result of increasing customer demand and additional testing requirements, the design of a new assembly line became necessary. At this stage, the company decided to apply lean manufacturing principles. One of the first steps was to determine takt time.
The takt time for this product of 40 s was calculated based on the highest demand. Given the 50-second rule, the engineers responsible for this project decided to design either one 80-second takt time assembly line running in two shifts, or two 80-second takt time assembly lines running in one shift. Work on designing the assembly line was offered to several engineering companies. According to their estimates, the design of one line required from 280 to 450 thousand dollars. The development of two lines meant doubling the equipment units and the amount of initial investment capital. However, by using two conveyors, each could be configured to produce specific types of products, allowing production to become more flexible. In addition, increased productivity, employee satisfaction, and reduced safety and quality costs can offset the cost of designing an additional line.
Thus, by adhering to the simple rule that the speed of any manual operation should not be less than 50 seconds, losses can be avoided. When designing lean manufacturing processes, it is necessary to use the 3P (Production Preparation Process) method 1 and conduct a thorough analysis of takt time.
1 A method of designing a lean manufacturing process for a new product or fundamentally redesigning the manufacturing process for an existing process when there is a significant change in product design or demand. For more information, see: Illustrated Glossary of Lean Manufacturing / Ed. The Marchwinskis and John Shook: Trans. from English M.: Alpina Business Books: CBSD, Center for the Development of Business Skills, 2005. 123 p. Note ed.
Based on the article Job Miller, Know Your Takt Time
and books by James P. Womack, Daniel T. Jones Lean Manufacturing.
How to get rid of losses and achieve prosperity for your company.
M.: Alpina Business Books, 2004
prepared by V.A. Lutseva
Production characteristics
Working hours and time funds
The working hours include 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: 24,363 = 8670 hours.
Excluding weekends and holidays, based on a five-day working week of 41 hours, we obtain a nominal time fund FN = 4320 hours.
We take into account equipment downtime for repairs; FD is the actual annual operating time of equipment during 2-shift operation.
FD = 3894 hours.
Determination of the release stroke
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.av. manufacturing the product at the main operations.
The release stroke is determined by the formula:
(min/piece) (3.3.1)
where Fd = 3894 hours;
Ng = 20000pcs - annual parts production program;
fs = 3894 60/20000 = 11.7 min/piece
Definition of production type
The type of production can be determined by the numerical value of the operation consolidation coefficient, which is calculated according to GOST 3.11.08-74. Approximately, the type of production can be determined by the value of the coefficient - Ks
where Tsht.sr is the average piece production time of a product, determined according to the data of the current technical process.
Tsh.sr. = 71.43/17 = 4.2 min.
Kzo =11.6/4.2=2.7
1< Кс?10 - крупносерийное производство
Analysis of the manufacturability of the design of the “Drive shaft” part
Manufacturability is a property of a product, according to which the design of the part must correspond to the application most progressive methods processing or assembly during manufacture.
Rational designs of machines that provide the necessary operational requirements cannot be created without taking into account the labor and material intensity of their production. Compliance of the machine design with the requirements of labor intensity and material intensity determines the manufacturability of the design. When objectively assessing the manufacturability of the design of machines, their parts and assemblies, a number of positive factors that determine the manufacturability of the design are taken into account.
When objectively assessing the manufacturability of the design of machines, their parts and assemblies, a number of positive factors that determine the manufacturability of the design are taken into account. These include:
The optimal shape of the part, ensuring the production of a workpiece with the smallest allowance and the smallest number of machined surfaces;
Lightest machine weight;
The smallest amount of material used in the construction of machines;
Interchangeability of parts and assemblies with optimal tolerance ranges;
Normalization (standardization) and unification of parts, assemblies and their individual design elements.
The basic requirements for the manufacturability of the design of mechanical engineering parts are set out in the literature.
The design of the part must consist of standard and unified structural elements (CED) or be standard in general. Parts must be made from standard or standardized blanks. The dimensions of the part must have optimal accuracy. The surface roughness must be optimal. The physical, chemical and mechanical properties of the material of the part, its rigidity, shape, dimensions must comply with the requirements of the manufacturing technology (including processes of finishing and strengthening treatment, application of anti-corrosion coatings, etc.), as well as storage and transportation.
The base surface of the part must have optimal accuracy and surface roughness, which ensure 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 specified output volume and the type of production. The method of manufacturing parts must allow the simultaneous production of several parts. The design of the part must ensure the possibility of using standard and standard technological processes for its manufacture.
We will test the manufacturability of the “Drive Shaft” part for manufacturability in accordance with Methodical instructions.
