Poka Yoke Techniques to Help Eliminate Waste
If you haven’t heard of Poka Yoke before, you might think you’ve accidentally stumbled onto the wrong website and are about to read a writeup on a strange dance phenomenon. In actuality, Poka Yoke techniques are the strategies used by professionals in order to minimize defects or mistakes in an industrial manufacturing setting. Like many Techniques of our time, Poka Yoke can trace its origins back to the ‘Toyota Production System’, as described therein by Shigeo Shingo.
As an honorary (if not undermentioned) Lean technique, Poka Yoke helps to eliminate waste by ensuring that defective products don’t use up your materials, manpower, or production time; even a defect that can be re-worked, and therefor doesn’t result in material loss, wastes time and energy. In this blog post, we’re going to break down Poka Yoke and go into some specific ideas you can keep in mind to make your own implementation as effective as possible. Hopefully, it’ll help to kick-start your thinking about how you might work this valuable tool into your place of work.
Poka Yoke, literally translated, means to mistake proof a system. Before, however, different words were used and the concept was called “fool” or “idiot” proofing. While the more sensitive name is the one that was republished a million times over in training literature and Lean manuals, sometimes a nod to the original translation can be useful. That is to say, one of the most effective ways to implement Poka Yoke is to feign ignorance. Here’s what I mean:
The ‘Dummy’ Walk: Other people may have a more scientific name for this, though I refer to it as the dummy walk tongue in cheek. Really, you’re not pretending to be an imbecile or someone with a low IQ, what you’re trying to do is place yourself into the shoes of someone who is completely unfamiliar with your business.
Walk through an operation step by step, and think about, if you were someone with no experience in the industry, how you would know what to do. “But wait, my workers are trained,” I can hear you saying, “this would only be helpful if I never trained my workers in the first place!” The truth of the matter, however, is that accidents happen, people get tired, etc. Keep in mind that the end result of this technique isn’t necessarily to design an assembly line a toddler could operate, but in looking at production in such a way you will pick out the bigger problems rather quickly.
As an example, let’s say workers inspect and feed finished toy blocks into a chute to be packaged near the end of assembly. If you notice that every once in a while a defective block slips through, one Poka Yoke technique you could implement is a guarding device that is cut to only allow the correct pieces through.
The goal of a dummy walk is accomplished then by observing the process in the shoes of someone with no previous knowledge, identifying a potential problem, and then implementing a fix or failsafe to account for it.
Close Proximity: One Poka Yoke technique that is often overlooked is the importance of close proximity. This concept can be applied to a number of other strategies as well. Basically, the proximity rule with Poka Yoke means that it’s best practice to place any kind of control or defect-reducing mechanism as close to the process you’re trying to control as possible.
This is helpful for a number of reasons, but the big one is isolation. The closer a device is to the things it’s supposed to deal with, the more likely you are to interact with the intended factors and the intended factors only. In our example above, maybe there’s a final step after inspection where a final piece is affixed to the blocks. With this final piece, the blocks wouldn’t fit through the custom guard. Obviously, you wouldn’t want the defect guard on after that step or you would experience unwanted interaction between the Poka Yoke device and a stage of production.
Obviously, that’s an overtly obvious and silly example, but in the real world much more subtle activities or factors between a device and the issue its intended to fix may not be noticed until it’s too late; the last thing you want is to waste money on installing or implementing something that just has to be removed and done over again, yikes! If you’ve already got a few defects in your production cycle, the last place you want them showing up is in the measures meant to address those very problems!
The Factors of Any Good Poka Yoke Technique
In addition to proximity, there are several other factors that can quickly tell you if you’re implementing Poka Yoke in a way that is likely to be effective.
1. They’re natural. Poka Yoke devices should fit naturally into an already existing process; implements that deviate too much form what’s established can become to time consuming in and of themselves to be of net benefit to you.
2. They’re not complicated/expensive. Likewise, techniques or fixes that are overly complicated (hard to learn) or that cost a lot of money to implement can dramatically increase the time it takes for them to ‘pay off’ in decreased defect rates and time saved day to day. Try to boil any ideas you have down to their very simplest elements before implementing them.
You may even come up with a few rules of thumbs through your own trial and error, but hopefully these will help guide you a bit, at least when you’re starting out.
One of the closing thoughts I want to leave you with is that Poka Yoke can really be anywhere and be anything. Even when we talk about specific Poka Yoke ‘techniques’ the best advice I can give you is to let your own implementation be creativity-lead. Don’t know if someone’s done it before? Who cares! Your business is its own unique machine, treat it like one.
- Quality Control in Manufacturing– creativesafetysupply.com
- What is Poka Yoke?– blog.creativesafetysupply.com
- Poka Yoke – Mistake Proofing– lean-news.com
- What is Poka Yoke?– 5snews.com
- Safety Lean Manufacturing – 5 Ways to Combine Safety and Lean– iecieeechallenge.org
- Tips and Techniques for a Visual Workplace– aislemarking.com
- Safety Supervisors – The 5 Most Common Mistakes– realsafety.org
- Connection between 5S and Lean– blog.5stoday.com