After reading some Lean text books and possibly attending a conference or two many “Lean Dreams” are crushed when the practitioner is told, “Friend, there ain’t no way we are converting that $4 million paint line into some fancy little cell. You just go do some more 5S and leave the plant layout to us engineers.”
After hearing this the now baptized Lean practitioner pauses and wonders what to do next. Never fear… there are ways to deal with situations like this. One of the techniques that can be employed is to develop what is known as a tsurube system.
The Japanese phrase “tsurube houshiki” describes how a two bucket system draws water from a well. While one bucket is headed down into the well another bucket is headed back up the top.
Staying with the $4 million paint line theme let’s look at a portion of a value stream map to demonstrate how this tsurube system might look (click picture to enlarge it).
There is a finished goods supermarket located after process C which has a pre-determined amount of material (pitch) withdrawn every 30 minutes. Once this withdrawal occurs a production kanban is sent to process A. This tells A to start producing; assuming of course the FIFO lane after it had not reached its capacity. From here we begin the “two bucket” system as described in the well example.
Every 30 minutes the same numbers of parts (bucket 1) are transported from the FIFO lane after process B to the paint line at the same time parts (bucket 2) are transported from the paint line to process C. While this is not the prefered one piece flow it is far superior to traditional mass production techniques.
Not ideal, but better than alternative
To be sure, it would be optimal to not have a decoupled paint line, but sometimes we must deal with the cards dealt us. In situations like this a tsurube system may be the answer.