I recently saw a question posted on the iSixSigma forum that went something like this, “How can Six Sigma enhance the just in time process?” I thought this was a great question and will offer my two cents on the topic this evening.
As many of you may know Just-in-Time, or JIT as it is often referred, is a pillar of the Toyota Production System (Jidoka is the other pillar with Heijunka being the foundation).
In order to work in a just in time manner several things must happen. At a very basic level material must flow through the process only after being pulled by a downstream process. No one produces anything until requested… and once they are requested they produce only that which was asked for really fast! And this awesome orchestra (and awesome it is when properly working) is paced by the steady beat of Takt Time.
Now, obviously, this is vastly over simplified but I want to make another point so will not offer a thesis here in the principles of JIT.
OK, to my point. One of the prerequisites of any Lean system is a capable process. If someone were to setup a nice level pull system within an ergonomically conscious U-shaped cell, with correctly calculated Standard WIP in place, and beautifully developed visual controls on display they may feel really good.
But guess what… if this process only produces 4 good widgets for every 10 made trouble, as my late Grandma used to say, God rest her soul, is a brewin’!
The beauty, and sometimes initial discomfort, of a Lean system is all the “protection” of excess inventory (one of the 7 deadly wastes) is gone. There is nothing to hide behind! So issues like defects and incapable processes get brought to the forefront immediately and scream for attention.
This, my friends, is where Six Sigma can and should shine. Eliminating defects and killing variation is what Bill Smith invented Six Sigma for back in the mid 1980’s!
The DMAIC (Define, Measure, Analyze, Improve, and Control) process is the perfect roadmap to solve these defect and capability issues. Tools like process mapping, C&E Matrix, FMEA, Measurement Systems Analysis, Capability Studies, Hypothesis Testing, Regression, DOE’s, and Control Charts (to name a few) enable us to identify, quantify, fix, and control these issues once and for all.
You may be saying, sure but this is common sense. But if a Lean practitioner is not aware of the best and most efficient way to eliminate defects and reduce variation (that would be DMAIC) their Lean system may fail or take longer to take hold then was necessary. Conversely, if all a Six Sigma practitioner does is eliminate defects and variation they have left lots of improvement on the table.
So this is yet another perfect example of how Lean Manufacturing and Six Sigma complement each other perfectly and why I believe they should be joined at the hip.
I received an email on this very topic of how Six Sigma and JIT relate that I will close with. It sums things up nicely.
Ron,If you need a quote from 1950 by Deming, look at the foreword of the anniversary edition of Shewart’s 1931 Quality Control book. Deming explicitly uses the term waste in the context of his 1.5 page summary of quality. To me the more interesting question is how the concepts of waste and quality could be separated to a degree that we now have to piece it together again.
Until next time, I wish you all the best on your journey towards continuous improvement!