1, the characteristics of lean production

All production activities of lean production are based on forecast and driven by production demand, and one of its core goals is zero inventory or making inventory reach the ideal minimum state. The benefits of doing so are not difficult to predict. Inventory management has become one of the key points of enterprise management. From the initial extensive inventory management to the later systematic management methods, such as push inventory management and pull inventory management, we see more and more lean production. The advantages of reducing inventory, reducing cost, shortening product sales cycle and reducing enterprise risk are self-evident. The production process is fast and flexible, and the enterprise and the market environment are harmonious and unified.

The rapid changes in today's market make this feature of lean production particularly prominent and important. In order to cope with the rapid changes in the market, lean production is flexible. Lean production department can transform the production indicators, processes and even equipment in the factory in a very short time, thanks to the high attention paid by lean production to the cooperation degree of each production link. Flexible production design not only reduces the cost and improves the efficiency, but also invisibly increases the factory's ability to resist market fluctuations.

Different from the previous production methods, lean production attaches great importance to the cultivation and utilization of employees and human resources. In this fine and flexible mode of production, people's wisdom and creativity become particularly important. As front-line employees who are very familiar with machines and operation processes, they are most likely to find the shortcomings and improvements in the production process, and lean production provides them with a possibility to transform the current production model.

For example, the last process in the stator production workshop of automobile motor is to take the parts and put them in the box. The basic flow of this action is that the workers pick up the original child from the exit of the previous process, turn around and put it into a special plastic box for inspection. This small step is reflected in the workers, which is tiring and time-consuming, because it takes two turns to extend the arm down to the original shape and then put it in the box. It took the lean production department almost a day to come up with an improvement scheme: design a conveyor belt to convey the workpiece, set a shelf at the end of the conveyor belt to put the boxes, and set them on the same side of the workers to unify the horizontal height. In this way, the original action takes 15 seconds, and now it only takes 5 seconds. The labor intensity of workers has decreased, and the result of triple efficiency improvement can be imagined.

On the premise of reducing inventory and flexible production, production quality has become a point that lean production must ensure. The increase of defective product rate and the investment of post-event maintenance and remedy will undoubtedly greatly reduce the overall effect of lean production, or even completely lose its significance. In the lean production transformation projects of most factories, the most common ones are the reasonable adjustment of production processes and the flexible combination and design of production lines. Factories and technicians often need to spend some energy to observe and study a reformed production line, and obtain stable results and data before they can be applied on a large scale. Such reasonable transformation steps, coupled with the flexible characteristics of lean production, provide a great space for the factory to improve the product qualification rate, and even after finding design defects, it can be quickly changed and adjusted to minimize losses.

2. Limitations of current lean production.

Lean production originally developed in large and medium-sized enterprises, in which the degree of mechanization is high, the division of labor in production links is obvious, and quantitative change causes qualitative change, especially when each link carries out relatively simple and repetitive production operations, a small adjustment and change can often bring great improvement, which is reflected in the whole production scope and long time span, and continuous improvement and adjustment can finally achieve a better production state. However, it is precisely because of this characteristic of lean production that it has certain limitations.

Lean production is an accumulation process. One-time transformation can solve some problems, but it is difficult to improve the final production efficiency overnight. Lean production is difficult to play a role in industries where product upgrading is very fast and production technology requirements change at any time.

Theoretically, the whole process of lean production is greatly influenced by the change of demand. Most enterprises implement kanban system, that is, the next process is subject to kanban, the last process produces parts, and the last process needs the production materials of the last process, and so on, that is, the product demand determines the production demand of the last process. After the first production process receives the instructions from the rear, the whole production process begins. This is a flexible mode of production, but it still lags behind. The latter process is directly affected by the former process, and the initial stage of production is in a waiting state. When the dynamic change of product demand is very fast, due to the lack of inventory, normal delivery will fail. Although many enterprises have put forward many rectification measures to solve this problem, it is still a difficult problem in lean production. Therefore, the lag of lean production and the ultimate goal of zero inventory are contradictory. In order to cope with the ever-changing market demand, some enterprises have to keep a certain inventory while implementing lean production.

It is very difficult to implement lean production in factories that produce many products and small batches. This is aimed at enterprises that produce many kinds of products and have great technical differences, but for those enterprises that have little difference in production technology and whose products can even be used in the whole production line, this problem is much smaller. It is difficult for factories with complex production process, large line difference, difficult production scheduling and numerous bottlenecks to adopt lean production. This is because the production process is too complicated and various materials need to be fully prepared. Due to the overlapping of some processes, production scheduling becomes very difficult, and it is difficult for many production links to pull production at the same time, which requires that the production cycle must be extended in advance to ensure the normal satisfaction of product demand.