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| Originally envisioned by Henry Ford, and made operational by Taiichi Ohno of Toyota in the early 1950's, the Just In Time (JIT) production system or technique is the coordinated manufacture of components or products so that they arrive at their destination "Just in Time". This meant the right part, in the right place, at the right time. Therefore the beginning of the single unit manufacturing system. |
| Since only one unit was require at any time, the work in progress (WIP) inventory is reduced to the number of workers in the production system. Each person performs work on the product (adds value) and hands it directly to the next worker. The product is never disposed to a table or bin, then picked up by the next worker, therefore no wasted time in the disposal and pick up activities. This is actually not as difficult to coordinate as one might think. Slower operations are set up in multiples to absorb the incoming production. Faster operations are combined to make the production time greater and evenly divisible into the downstream operation's production time. |
| The greatest savings is in the JIT "Bumping" system. This method of JIT production eliminates the workers "ownership" of an operation. Even in the standard JIT system, after a worker hands the part to the next worker, it is possible that they would wait for the upstream operation to complete their task before handing it to them. This is eliminated in the JIT "Bumping" system. Instead of requiring a worker to wait for the operation to be completed, they simply take over the completion of the upstream task, then complete their task plus continue with the downstream task until bumped. |
| For example, if the operation in question is threading a set of 4 bolts on a flange and only 2 have been started, there is no need for the downstream worker to wait, they would take the remaining 2 bolts from their co-worker and finish the operation. With this procedure, the production line or cell would have the worker perform the final operation (dispose the finished product) move to their upstream co-worker and "bump" them or take over the operation being performed at whatever stage it is in. That worker would "bump" their upstream co-worker, and so on until the first worker would be bumped and they would collect the first parts and start a new assembly. |
| One of the flaws in the standard JIT system is when there is a problem with one of the operations, the whole line must stop. With the bumping system, the worker with the problem would back out of the production line and correct the problem, then re-enter the line when the problem is solved. If the operation involves a machine, the spare machine is used. The only full line stoppage occurs in the case of large, expensive equipment that would not be duplicated (i.e. a paint booth malfunction). |
Information on the JIT Workshop
Lean Manufacturing
Value Stream Mapping