Decreasing work in process is one of the basics of lean manufacturing because of many reasons. Recently, I had an experience that really shows one of the benefits of decreasing WIP which is decreasing chaos. We have been working successfully on decreasing our WIP for several months and one of the results was less calls from sales to expedite the processing of specific semi finished products because every thing is flowing in a queue and there is no waiting before down stream processes.
In a certain month, we had to produce a large contract that required certain stage to be slightly overloaded, and after few days operators discovered that there was a quality problems that required rework of certain quantity which resulted in more overloading of that step. We tried to decrease the WIP going to that machine but later on we had to produce other contracts which needs the processing of that machine and other machines as well. Simply, in that month we couldn’t control our line balancing and our WIP increased to some extent.
What was very obvious is that we started receiving requests from the sales people to process this contract ASAP and we had to to set priorities for processing the WIP in several stages. Any delay our deviation from our priorities meant more chaos.
Decreasing WIP through line balancing and mixed production model makes products flow smoothly without the need to set priorities or to ask anyone to process anything ASAP because everything is by default processed ASAP. If you add proper maintenance and less quality problems to the line balancing and Mixed production model then you get a very smooth operation. At that time, you can set very accurate delivery time and everyone will be working in a good stable working environment.
