Lean Manufacturing

The differences between these two production systems are very clear, in fact it can be said that they are the total opposite of each other in terms of their approach to, and methods of, production.

One of several aspects of the Toyota production system that differ from The GM system is that Toyota puts a flow into the manufacturing process, while GM has lathes located in the lathe area, milling machines in the milling area Toyota places a lathe, milling machine and a drilling machine in the actual sequence of the manufacturing process. This means that instead of having one worker per machine, one worker oversees many machines or processes. GM, however, has a group of workers skilled only in lathe operation, a group skilled only in milling. The GM plant layout will have 50 or more lathes in one location. When machining is completed the items are collected and taken to the subsequent drilling process, and after that the milling process. In the US there is a union for each job function, with many unions in each company. Lathe operators are only allowed to operate lathes and a drilling job must only be taken to a drilling operator. As a result because the operators are single skilled a welding job required at the lathe section cannot be done there but must be taken to a welding operator. As a consequence there are a large number of people and machines and for GM, mass production is the only way to achieve cost reduction under such conditions. When large quantities are produced, the labour cost per car and depreciation burden are reduced. This requires high performance, high speed machines that are both large and expensive. This type of planned mass production is a system in which each process makes many parts and forwards them to the next process. This method naturally generates an abundance of waste.

The basis of the Toyota production system is the absolute elimination of waste. The two pillars needed to support this are: -

§Just-In-Time

§Autonomation (automation with a human touch)

Just-in-time (JIT) means that, in a flow process, the right parts needed in assembly reach the assembly line at the time they needed. Toyota establishing this flow throughout can approach zero inventory. From a production management point of view this is an ideal state. However, with a product made from thousands of parts like a car, the number of processes involved is enormous. It is extremely difficult to apply JIT to the production plan of every process in an orderly way. Therefore to manufacture using JIT so that each process receives the exact item needed, when it is needed and in the quantity needed, conventional management methods do not work well. The conventional way (and the way GM manufactures) was to supply materials from an earlier process to a later process. Toyota uses the reverse; a later process goes to an earlier process to pick up only the right part in the quantity needed at the exact time needed. This makes it logical for the earlier processes to make only the number of parts that are withdrawn. In terms of communication it simply requires what and how many are needed. Toyota calls this means of indication 'Kanban' and allows parts to be pulled into the production line not pushed, as they are in the GMs production process as GMs mass production system relies on having a large inventory available so that the parts can be moved from the warehouse when needed This generates high storage costs that Toyota simply does not have to worry about. This is controlled through a MRP and a MRPii system.

The second pillar of Toyotas' system is called autonomation though this is not to be confused with simple automation. GM favours machine automation and because today's machines have such high performance, a small abnormality such as a piece of scrap falling into the machine can damage it and hence defective parts are soon produced and with a machine of this type mass production of defective parts cannot be prevented. Toyotas autonomination is also known as automation with a human touch and is a machine that is attached to an automatic stopping device as well as various safety devices and Baka-Yoke1 fool proofing systems.

Autonomation also changes the function of management as well. An operator is not needed while a machine is working normally, only when the machine stops because of an abnormal situation does if get human attention. As a result one worker can attend several machines, making it possible to reduce the number of operators and increase production efficiency. In addition to this if a worker is always watching the machine waiting for an abnormality to occur he will immediately repair it without the managing supervisor being made aware of it and so improvement will never be achieved and costs will never be reduced. As GM favours having one worker manning