Tsurube System
by Ron Pereira on May 29th, 2007
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.”
Tsurube System
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There is a finished goods supermarket located after process C which has a pre-determined amount of material (pitch) withdrawn every 30 minutes.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.
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I’m OK with Japanese buzzwords/phrases, but boy I get fatigued on them.
What you described here can also be called, more simply, a pull system or it’s also a version of a supermarket system.
“Flow where you can, pull where you can’t” is the one phrase I’ve heard. It’s “optimal” to not have decoupled processes, but if you have to decouple, it’s better to have a systemic pull system instead of relying on MRP.
I must confess I like the Japanese words. It keeps it real if you ask me. It’s just we have all grown so used to words like kanban and kaizen that less used Japanese phrases sometimes catch us off guard. Also, a tsurube is similar to a supermarket/pull system but has a few twists that you don’t read about in most text books… which is why it is important to call them by name in my opinion.
The tsurube system is not a supermarket system. There is no market of parts. It’s a two-bucket system, as Ron said.
It is a special type of a pull system, a type of Standard WIP as seen in Standardized Work, used to flow and pull through shared processes, batch processes or processes that are just far enough away so that moving one at a time doesn’t make sense.
A tsurube is a “pulley & pail” as you might see in an old-fashioned well. That’s what I call it to make it easier for people to remember.
The Japanese words are often off-putting to people. Not me, but I hear that from others. The language barrier can be a lean barrier, which isn’t good.
Thanks for the clarification though on the difference between this and supermarket.
Sounds like a variation of a 2-bin kanban system?
It’s not unlike the two-bin, though with two-bin it’s often a material replenishment method (from suppliers, stores or upstream processes) while the pulley & pail (tsurube) system is used exclusively between one process and the next in order to make a discontinuous process continuous.
Another important difference is that while there is an empty bin being returned as a signal in two-bin, the Standard WIP quantity for tsurube is 2x the “bucket” quantity or lead-time / takt time for the process that you are pulling from. There is never a totally empty bin / bucket, as such.
The full bucket returning (the pail being pulled up the well, if you will) is the signal to take the next batch of materials waiting to be processes. There are pieces “in the well” such as in a paint line or oven, and pieces that are in the pail outside of the well, being used one piece at a time. At the same time there is a pail being readied to go back into the well, one piece at a time. Much easier to demonstrate if you have some liquid, two cups, some cord and something to hang it over.
Thanks Mark and Jon for the good discussion.
John, do you have any idea how i can demonstrate this to myself. I’ve found some liquid, two cups, some cord, and rope to hang them. Any further instruction?
Thanks!
Hi Suwandi, I let Jon know about your comment as this is an older post. He may make a short video that I am sure we would all love to see in response to your question. Stay tuned and thanks for stopping by. BTW, Jon’s blog is http://www.gembapantarei.com so be sure to check his site out for some excellent lean blogging.