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Statistical process control (SPC) is generally a Six Sigma tool. A few people and organizations will use SPC as a stand-alone methodology. Generally, it is not a tool found in the lean toolbox because conducting SPC is considered, by some, to be a nonvalue-added process.
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However, there is a common, problematic phenomenon that undermines the success of the lean method for many of us. Our effort to eliminate nonvalue-added (NVA) process steps encourages us to develop a trustworthy process that doesn’t need monitoring so we can stop the NVA effort to monitor it. Unfortunately, change happens.
Here is an example of how the phenomenon bites many of us. It should sound familiar. A business gets manufactured components for its finished product from a small list of tried-and-true, trusted suppliers. The suppliers’ quality processes and systems have been evaluated with careful scrutiny. The delivered components have been measured and tested until the business declared these suppliers worthy of the “preferred” or “partner” supplier list, and on-going measurements and tests are no longer required.
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Comments
Hear, hear!
As someone who works in both these worlds, I'm often shocked to hear lean practitioners tell me that SPC is NVA. I have watched some of these people do value stream mapping, taking one cycle time here, counting WIP there, and then drawing conclusions about process throughput capability from those single data points. SPC, used wisely (as Alan suggests in this article) will make your processes leaner and keep them that way with less waste. He also makes an excellent point about using lean thinking to remove the waste from data collection systems. Measurements don't have to be difficult or add processing steps; many can be done in-line or on-line.
What you said
I agree with both commenters - SPC is not NVA.
I'm resisting the urge to demonize people who think that way. My impression (unsupported by data, but IMHO very true) is that there are "Lean people" and "Quality / Six Sigma people". The Lean types are focused on flow, visual factory, etc. and don't leave their sandbox.
I read a funny / tragic anecdote on LinkedIn about malfunctioning hard drives leading to an extended line stoppage. The Engineers went into a DOE frenzy that consumed days. Finally someone randomly visited the work area and found an operator doing a workaround that lead to the failures. Classic DUH moment.
SPC and Lean
I am surprised to hear that some, or any, "lean practitioners" might not consider SPC of paramount importance. Suppose that we consider that "lean" is about the elimination of waste from a process or a system (of processes). Ultimately, what is the cause of waste in the system? It is the variation that is inherent in the system. Such variation (mura) will create conditions of too much (muda) or too little (muri).
For example, one of the foundational principles of lean is to build to takt time. Why? To eliminate the variation in demand. Another foundational principal of lean is heijunka. Why? To organize lumpy, random demands into a consistent repetitive pattern; to eliminate some type of variation. Generally, what is the purpose of visual control? To identify something that is abnormal, that varies from the expected. There are many other examples.
SPC is not a quality control gimmick. It is the study of variation. It is about understanding the variation inherent in the process. And it is the only way to understand such variation.
Historically, if Taiichi Ohno is the father of lean, then someone like W. Edwards Deming is the grandfather of lean and Dr. Walter Shewart is the great-grandfather of lean. I think it all started there.
Toyota uses SPC
In a recent Toyota San Antonio visit, a tour attendee asked if they use Six Sigma. The answer was no, but they use the 7 basic QC statistical tools, which includes control charts, of course. They just don't have "belts" or that formality. I'm sure they have engineers who know advanced statistical methods (as every automaker has had for a very long time).
TL;DR
That's what PPAP is for. Did you mention it?
PPAP
About PPAP (via wikipedia)
Who says that about SPC?
In my career, I learned and used SPC before really getting to apply Lean principles. Even GM, circa 1995, had SPC charts on the line (whether or not management used them properly was a different story, altogether).
Granted, many Lean people are not taught SPC in their Lean curriculum and that's a shame.
That said, I've never heard a Lean person say SPC is "non value added" in that a company should STOP doing it. Keep in mind that there are two types of NVA activity in the Lean approach... the "required waste" that we have to keep doing in the short term because there's no better alternative (such as inspection... Toyota still does final inspection in their plants) or "pure waste" (such as batching, delays, etc.) that we can stop doing immediately with no ill effects.
I'd rather see the author write articles about why SPC is important, rather than taking what might seem like an overly broad slap at Lean.
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