“SEIRYUKA” or Smooth Production　

In Toyota, MUDA found in operators’ motion is eliminated by the second. This activity never means shortening the value-added time called net operation time, such as processing time including fastening screws, because such contraction of net operation time may possibly lead to defective products or a great deal of stress on operators. Instead, we should pay attention to the stagnant time spent before and after the net operation. Stagnant time is found when items are transported, waiting for the next stage of processing, stagnating due to a big lot size or being detained on the long belt conveyer, or when operators are looking for parts or jigs, waiting for instructions from their bosses or examining whether products are good or bad.

As far as a factory keeps manufacturing products through several processes, they see the repetition of “stagnant time + net operation time + stagnant time + net operation time….” Contraction of net operation time is difficult and not effective, even if possible, with the reduction by the second. When it comes to stagnant time, however, it is rather easy and possible to reduce—lead time for instance—by the hour or day. “SEIRYUKA” is thus a process for completing products in a smooth production flow by shortening the lead time between manufacturing processes and reducing the inventories of WIPs.