It can be seen that the practical application of JIT contains complex contents, and the implementation means and tools are also different due to different enterprises and production methods.
During the production interval, it is necessary to place the equipment and raw materials reasonably. Rapid assembly, replacement and adjustment provide an important basis for meeting the production requirements of frequent assembly of parts and components in the later process and balanced production of "multi-variety and small batch". However, this complicated product collection method will inevitably increase the transportation workload and transportation cost, especially in the case of inconvenient transportation, which will affect the smooth progress of just-in-time production. The reasonable arrangement of equipment, especially the "combined U-shaped production line" formed by connecting U-shaped units, can greatly simplify the transportation operation and increase the transportation times of parts and products per unit time, but the transportation cost does not increase or increases very little, which provides a foundation for frequent transportation in small batches and single-piece production and delivery. What is lean production? Lean production is also called excellent production, in which "fine" means excellent, accurate and fine; "Profit" means profit, benefit and so on. Lean production means timely manufacturing, troubleshooting, eliminating all waste, and moving towards zero defects and zero inventory. It was put forward by MIT in a research project called "International Automobile Plan".
After doing a lot of investigation and comparison, they think that JIT of Toyota Motor Corporation of Japan is the most suitable production organization and management model for modern manufacturing enterprises, which is called lean production to solve the problem that mass production methods in the United States are too bloated. Lean production combines the advantages of mass production and single-piece production, and strives to achieve low-cost production of multi-variety and high-quality products in mass production. Toyota production mode is also called fine production mode or lean production mode.
Lean production is a change in system structure, personnel organization, operation mode and market supply and demand, which enables the production system to quickly adapt to the changing needs of users, streamline all useless and redundant things in the production process, and finally achieve the best results in all aspects of production, including market supply and marketing.
The origin of Lean Production Lean production (LP) is praised as JIT(Just In Time) production mode of Toyota in Japan by experts from the International Automobile Planning Organization (IMVP) of Massachusetts Institute of Technology. Fine, that is, less but fine, without putting in extra production factors, only producing the necessary number of products urgently needed by the market (or products urgently needed by the next working procedure) at an appropriate time; Benefit, that is, all business activities should be beneficial and effective, and there should be economic benefits. Lean production mode originated from Toyota production mode and was organized by experts and scholars from America 17 countries. It took five years and cost $5 million. Taking the automobile industry, a typical industry that pioneered JIT in mass production and lean production, as an example, this paper makes a theoretical summary. The advantages of lean production mode are not only reflected in manufacturing system, but also in product development, cooperation, marketing network and management. It is the best production organization system and mode in the industry at present, and it will surely become the global standard production system in 2 1 century.
Lean production mode is the product of "resource scarcity" and "multi-variety, small batch" market constraints faced by Japanese automobile industry after the war. It began with Toyota Sasuke, formed with the joint efforts of Akio Toyoda, Ichiro and Taiichi Ono, and gradually improved in the 1960s.
Characteristics of lean production: pull-type just-in-time production
Taking the demand of end users as the starting point of production, we emphasize the balance of logistics, pursue zero inventory, and require the parts processed in the previous process to enter the next process immediately. Organizing production lines depends on a form called kanban. That is, kanban conveys the information of the next upward demand (the form of kanban is not limited, the key is to convey information). The rhythm in production can be manually intervened and controlled, but the key point is to ensure the logistics balance in production (for each process, it is to ensure the timely supply of the material return process). Because it is pull production, the planning and scheduling in production is essentially completed by each production unit itself, and centralized planning is not adopted in form, but the coordination between production units is extremely necessary in the operation process.
total quality control
It is emphasized that quality is produced rather than tested, and the final quality is guaranteed by quality management in production. Quality inspection and control in the production process run through every working procedure. It is important to cultivate the quality consciousness of every employee, pay attention to the quality inspection and control of each working procedure, and ensure that quality problems are found in time. If quality problems are found in the production process, the production can be stopped immediately according to the situation until the problems are solved, so as to ensure that there is no ineffective treatment of unqualified products.
For quality problems, it is generally to organize relevant technical and production personnel as a group to work together and solve them as soon as possible.
Team work method
Team work method (team work). Every employee not only carries out the orders of his superiors at work. What is more important is to actively participate and play the role of decision-making and auxiliary decision-making. The team-building principle is not completely divided according to administrative organizations, but mainly according to business relations. Team members emphasize one specialty and many abilities, and are required to be familiar with the work of other team members to ensure the smooth progress of work coordination. The evaluation of team members' work performance is influenced by the internal evaluation of the team. This has a lot to do with Japan's unique personnel system. The basic atmosphere of team work is trust, with a long-term supervision and control as the main task, while avoiding auditing every step of the work and improving work efficiency. The organization of the team is changeable. Different teams are established for different things, and the same person may belong to different teams.
concurrent engineering
Concurrent engineering. In the process of product design and development, conceptual design, structural design, process design and final demand are combined to ensure the required quality to be completed as soon as possible. All the work is done by the relevant project team. In this process, team members arrange their own work, but they can give feedback regularly or at any time to coordinate and solve problems. Feedback and coordinate the whole project according to the appropriate information system tools. Using modern CIM technology, in the process of product development, the parallelization of project process is assisted.
Comparison between lean production and mass production management thought: as a brand-new management thought, lean production is successful in practice, not simply applying one or two new management methods, but a management system that is highly integrated with enterprise environment, culture and management methods, so lean production itself is an autonomous system.
(1) The mass production mode with different optimization ranges originated in the United States, which is based on the relationship between enterprises in the United States, emphasizing market orientation and optimizing resource allocation. Each enterprise takes the financial relationship as the boundary and optimizes its own internal management. And related enterprises, whether suppliers or distributors, treat each other as rivals. Lean production takes the production process as a clue and organizes closely related supply chains. On the one hand, it reduces the transaction cost in enterprise cooperation, on the other hand, it ensures stable demand and timely supply, and takes the whole large production system as the optimization goal.
(2) Different attitudes towards inventory. The inventory management of mass production emphasizes that "inventory is a necessary evil". The inventory management of lean production mode emphasizes that "inventory is the root of all evil". Lean production model regards all inventory in production as "waste", and at the same time thinks that inventory covers up the defects and problems in production system. On the one hand, it emphasizes the guarantee of supply to production, on the other hand, it emphasizes the requirement of zero inventory, thus constantly exposing the contradictions in the basic links in production and improving them, and constantly reducing inventory to eliminate the "waste" caused by inventory. Based on this, lean production put forward the slogan of "eliminating all waste". Pursue the goal of zero waste.
(3) The concept of business control is different from traditional mass production. The employment system is based on the "employment" relationship between the two parties. In business management, the principle of efficient division of labor is emphasized, which is promoted and guaranteed by strict business audit. At the same time, the audit work also prevents the negative impact of personal work on the enterprise. Lean production originated in Japan and was deeply influenced by oriental culture. In the professional division of labor, we emphasize mutual cooperation, streamline business processes (including unnecessary verification work)-eliminate "waste" in business.
(4) The concept of quality is different. The traditional mode of production regards a certain number of defective products as an inevitable result in production. Lean production is based on the viewpoint of organizational decentralization and human cooperation, and it is feasible for producers to ensure the absolute reliability of product quality without sacrificing production continuity. Its core idea is that the cause of this probabilistic quality problem is not probabilistic in itself, and it is necessary to "eliminate the waste caused by all defective products" and pursue zero defects by eliminating the production links that produce quality problems.
(5) Different attitudes towards people. Large-scale production emphasizes strict hierarchy in management. The requirement for employees is to strictly complete the tasks assigned by superiors, and people are regarded as "equipment" attached to their posts. Lean production emphasizes individual intervention in the production process, giving full play to people's initiative and emphasizing coordination. The evaluation of employees is also based on long-term performance. This method regards employees more as members of enterprise groups than as machines. Give full play to the subjective initiative of the grassroots. Kanban is the most important management tool in JIT production, and Kanban is a production scheduling tool used to control the production site. Specifically, it is a card, and the form of the card varies from enterprise to enterprise. The information on kanban usually includes: part number, product name, manufacturing number, container form, container capacity, kanban number, transfer position and part appearance.
The function of kanban
In JIT production mode, Kanban has the following functions:
(1) production and transportation work instructions
Kanban records information such as production quantity, time, method, sequence, transportation quantity, transportation time, transportation destination, placement place and transportation means. Trace the assembly process back to the previous process one by one, and remove the kanban carried on the waste parts on the assembly line for collection in the previous process. This is how "post-process collection" and "JIT production" are realized through kanban.
(2) to prevent overproduction and overproduction
Kanban must be used according to established application rules. One of the rules is: "You can't produce or transport without kanban." According to this law, if the number of kanban is reduced, the output will be reduced accordingly. Because kanban only represents the necessary quantity, it can automatically prevent overproduction and correct delivery by using kanban.
(3) "Visual management" tool
Another application rule of kanban is: "Kanban must be stored in kind" and "the previous process should be produced in the order of kanban removal". According to this rule, the management personnel on the job site can see the priority of production at a glance, which is easy to manage. Through kanban, you can know the work progress, inventory situation and so on of the post-process
(4) Improved tools
In JIT production mode, the intermediate storage of WIP is reduced by continuously reducing the number of kanban. Generally speaking, if the inventory of WIP is high, even if the equipment fails and the number of defective products increases, it will not affect the production of the next process, so these problems are easily covered up. And even if there is a surplus of staff, it is not easy to detect. According to one of the application rules of Kanban, defective products cannot be sent to the next process. If the requirements of the next process cannot be met, the whole line will be shut down, which will immediately expose the problem, so improvement measures must be taken immediately to solve the problem. In this way, through the improvement activities, the problem has not only been solved. It also strengthens the physique of the production line and improves the productivity. The goal of JIT production mode is to finally realize the inventory-free production system, and Kanban provides a tool to move in this direction.
Five principles of kanban
Only when necessary, the post-process will get the necessary number of parts from the previous process: the existing processes and methods need to be completely changed.
The former process should only produce enough parts to supplement the parts collected in the latter process: under the first two principles, the production system is naturally combined into a conveyor belt system, and the production time is balanced.
Defective products are not sent to the next process: there is no inventory in the next process. Once defective products are found in the next process, production must be stopped, and this product should be returned to the previous process.
The number of kanban should be minimized: the number of kanban represents the maximum inventory of parts.
Kanban should be used to adapt to small changes in demand: according to market demand and the number of kanban taken in production emergencies, changes in plans will naturally occur.
Classification of kanban
In the actual JIT system, according to different needs and uses, the kanban used can be classified as follows:
Production card: (1) work-in-process kanban, (2) signal kanban; Record the types and quantities of parts and components that must be produced and ordered in the subsequent process.
Cash withdrawal card: (1) inter-process kanban, (2) external order kanban; Record the types and quantities of parts and components that the subsequent process should receive from the previous process.
Temporary kanban
Kanban and JIT
Kanban management can be said to be the most unique part of JIT production mode, so some people call JIT production mode "Kanban mode". But strictly speaking, this concept is also incorrect. Professor Yasuhiro Menda of Tsukuba University in Japan once pointed out: "Toyota production mode is a complete production technology complex, and Kanban management is only one of the tools to realize just-in-time production. It is a very wrong understanding to equate Kanban management with Toyota production mode. "
Because as mentioned above, the essence of JIT production mode is a production management technology, and Kanban is just a management tool. JIT production mode cannot be equated with Kanban mode. Kanban can only be used on the premise of process integration, production balance and production synchronization. If we mistakenly think that JIT production mode is Kanban mode and simply introduce Kanban mode without making any changes to the existing production management methods, it will not play any role. Therefore, when introducing JIT production mode and Kanban mode, the most important thing is to completely reorganize the existing production system.