In the book “Quest For The Dawn”, the written history of Toyota, the story is told of how Toyota Motor Corporation founder Eiji Toyoda and Toyota engineer Taiichi Ohno baffled manufacturing representatives and factory architects at the time with the blueprints for their first factory. There were no warehousing rooms for parts inventory anywhere in the plant. When asked where the parts would be stored, the two replied that the parts would be at the correct place in the production line at the right time and no sooner.
This is the simple theory behind Just In Time (JIT) Inventory.
In the Toyota Production System, a parts inventory is considered to be waste, not only in the cost of an inventory that just sits there but also in the overhead necessary to manage the warehousing rooms. JIT Inventory is the result of this philosophy.
The end result of a JIT Inventory system is that every product a plant manufactures becomes a special order. The product is ordered, and the build of that product is constructed in reverse to develop what’s needed to ensure the end product is built correctly. Arrangements are made to ensure the necessary parts are where they need to be in the production line at exactly the right moment as the product is built. Overhead pull lines along the production line allow any worker to stop the line if a part isn’t where it needs to be. Once a JIT Inventory system is implemented correctly and has its bugs worked out, line pulls to stop the line traditionally drop off to a manageable level.
It’s important to note that a lot of success in a JIT Inventory system has to do with the culture in the manufacturing facility. Workers need to be aware of how the system works, what they can do to assist in managing the system and most importantly, they need to have a considerable amount of patience during the debugging of a newly-implemented line.
