Poka Yoke or Mistake Proofing

I've had conversations about the term “mistake proofing,” a Lean Six Sigma term taken from Toyota's Production Systems “poka yoke,” which means to set up a work environment where mistakes are virtually impossible.  The definition: Mistake proofing, or its Japanese equivalent poka-yoke (pronounced PO-ka yo-KAY), is the use of any automatic device or method that either makes it impossible for an error to occur or makes the error immediately obvious once it has occurred. (Source:  http://asq.org/learn-about-quality/process-analysis-tools/overview/mistake-proofing.html  American Society for Quality or ASQ) Metaphorically speaking, the idea is if you poke an egg yoke while frying, it would prevent the mistake of it being under cooked, though some of us like it that way.

In past articles, I mentioned how Standard Operating Procedures (SOPs) can alleviate “hidden factories,” the cause for waste and lost revenues; and that management should take special precautions in training employees to perform at a high level of excellence.

Special measures irrespective to Lean Six Sigma methodology should be considered to engage employees to do their best. That means respecting their ideas and offering training in and outside of the company to develop the employee as an individual.

With that said jobs have five basic components.


(I’ve heard them called the five M’s or Man, Machine, Material, Method and Mother Nature).  Those of you familiar with Kaoru Ishikawa’s Fishbone Diagram are reminded of the Cause and Effect principles that uses these components to differentiate or isolate categories.  Since learning this concept, I am reminded of this diagram when an issue occurs and the Root Cause Analysis begins. 

After the initial interview, I consider the above components and determine a financial baseline.  Cost is one empirical method in collecting data that does not require detailed Measurement Systems Analysis or Gage Repeatability and Reproducibility (Gage R&R) or attribute data.  I simply pencil in an estimated cost based upon how much should be paid for a task in absence of waste, delays and defects.  Then I conduct a Time and Motion study on the task with the problems.   

I would hope after review the problems (through various methods such as asking 5 Whys, Value Stream and/or Process Mapping, and Affinity Diagram) I can determine the root cause.

What’s logical after drafting the appropriate paradigm the Ishikawa five components have been thoroughly evaluated and assessed.

Mistaking Proofing is part of the final Six Sigma Define, Measure, Analyze, Improve and Control (DMAIC) phase where steps are made to control and sustain a process once the decisions have been made.  With the right processes in place, I am hoping that that if consistently rendered, the ASQ’s mistake proofing definition “of any automatic device or method that either makes it impossible for an error to occur or makes the error immediately obvious once it has occurred” can be realized.

This posting presents a perspective on Mistake Proofing.  Problem solving takes a much longer process and utilizes a great many tools, so I plan to see the process out in real life examples.

Follow up blogs will be devoted to interviewing companies and logging isolated incidences that evaluates Root Cause and what Mistake Proof (as well as other effective) Measures were decided to mitigate future issues.

In the meantime, I asked Alan Kandel, close friend, colleague, engineer and writer to answer the question of mistaking proofing.  Currently, Kandel is retired and devotes his time to writing articles on California's air quality.

“What would I consider doing to mistake proof my company processes? Good question.

I think it would depend on the type of company, but let's say, for example, I opened up a business that manufactured sophisticated but portable equipment for monitoring air quality (purely fictitious, hypothetical, speculative) both in and out of doors.

I would want to know what the best processes were for manufacturing the gear, where the best locations would be to set up shop. I would want to do the necessary research to determine what the best methods of packaging and distributing said equipment would be, who the potential customers of said products would be and how to effectively market to them, not to mention develop a focus on how and whom to hire for the different and specific aspects of the type of work involved.

I would no doubt consult beforehand with those who have business-startup experience and expertise, those with a proven track record of success, in other words. I would also want to consult with those who could help outfit premises with all materials and equipment for setting up shop, this in association with finding out who the needed suppliers would be. Then I would want to find a method for determining the most efficient and cost-efficient way to manage processes and see to it that waste (in whatever form) was minimized or prevented completely.

Once established, a constructive and essential part of this operation would be to get employee input on a regular basis to see what could be done differently to improve the manufacturing processes. All employee input would be encouraged absolutely. This would be augmented to by creating a profit-sharing program where all employees could benefit if they chose to do so, but this would be their choice. I also believe that allowing employees to take breaks at times of their choosing is preferable to having set times for breaks (this is based on my own experience), but, again, I would want to get employee input on this first. Basically, to create a[n] effective business plan and then properly executing it.

This isn't rocket science, but creating and running a successful company should be methodically and meticulously thought out well beforehand. There is no room here for dysfunction of any kind.”

As you can see, a person does not need to be Lean Six Sigma trained to think up strong “mistake proof” solutions.  It’s just a matter of spending the time and energy to evaluate the problems and develop a strategy. 

It could just be that simple.

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