Why Lean Manufacturing? What are the disadvantages of traditional production methods

The traditional mass production method will cause the following waste:

1, work in progress more

Because the process (such as stamping, injection molding, etc.) need to have a mold change auxiliary time, mass production can be apportioned to each piece of the auxiliary time is relatively small, so in the large number of a product is manufactured in a very high production efficiency. But in the manufacture of different mixed products will produce a large amount of work in progress or inventory.

2, long production cycle

Production cycle is the product from the start of production to the completion of processing time. As in mass production, batch production, that is, a batch of the first production out of the product, to wait until the completion of the entire batch of products processed to flow to the next process for processing, resulting in a long production cycle. For example, in a manufacturing enterprise, *** have A, B, C, D four processes, the processing time of each process are 1min / piece. Batch size of 5 pieces, then every 20min to produce a batch of parts (5 pieces). Specifically the completion of each piece of time for: the first product from t = 0 moment, t = 16 moments to complete, after the production line time is 16min; the second product t = 17 moments to complete, and so on, the fifth product to be t = 20 moments to complete. And each piece of processing time in the four equipment for a total of 4min, it is not difficult to find that the delay is wasted on the batch waiting.

3, quality problems

In the mass production mode, especially in the machining industry, the equipment more than to take the group arrangement, that is, according to the function of the equipment is centrally located together. As mass production is a batch as a unit, from the previous process to the next process, as long as the next process of a device is available, it can be arranged for production, therefore, each batch of each machine may be processed, resulting in the logistics route is not unique, as shown in Figure 5-2. This flow is called "turbulence mode", the more processes, the higher the degree of turbulence. Once a defective product occurs, it is difficult to trace.

4, handling more

In the traditional machining industry, machinery and equipment, more than the use of group layout, in order to complete the processing of products, the need for the production process of semi-finished products in the production process of handling between the processes, this is the waste of inter-process handling, as shown in Figure 5-3. And along with the logistics, information flow also produces a break point. In order to reduce this waste, factories generally take the centralized production and centralized handling methods to reduce the number of handling, so not only the product processing cycle becomes longer, while the number of work in progress and the space required for production also increased.

Summary:

One of the core ideas of lean production is to try to make the number of WIP between processes close to or even equal to zero, that is to say, as soon as the end of the previous process is transferred to the next process for processing, the establishment of a kind of uninterrupted process, this kind of flow production is to realize the lean production of a basic principle.