Toyota Production System – Hello Lean Production – Part 5
Taiichi Ohno came away from the Ford plant with some thoughts. The first was that there was lots of waste littered around the plant. The next thought that followed was that it actually cost less when you make small batches of stampings rather than large production runs. The Toyota Production System advanced on this seminal thought.
He felt that there was a fundamental failure of mass production. The mass production philosophy is to make as many parts as possible. This means it is sacrosanct to stop the assembly line. Stopping leads to the greatest deficiencies. Ohno noticed that a defect was replicated over and over again. He ascertained that this actually decreased the efficiency of mass production and tremendously increased the waste.
The Big Step
Back in his factory in Japan he placed a cord at every workstation. He required his workers to pull the cord at the instant they determined a defect. This cord is called the andon cord and it halts the production line. Pulling the andon cord is a beacon for every one that could contribute to finding the root cause of the defect, to come and work on it.
Pulling the andon cord was part of the job responsibilities of each worker when they ran across a defect. It was well worth the time to correct the source of the defect. However, there was an initial pain with this requirement. Ohno and Toyota should be given a lot of credit here for sticking with this process. The initial implementation of the andon cord left the assembly line running in a series of spurts and stops. It is a credit to Ohno and Toyota’s insight and understanding of the manufacturing process that they did not stop.
Today Toyota’s plants yields approach 100%, mass production is at about 90%.