None of the MLG team is a fluent Japanese speaker. Ian has spent many happy hours in dojos (rooms in which judo is practised) up and down the country throwing and being thrown onto tatami (the mat), winning most of his contests using hip-throwing techniques such as Harai-Goshi or sweeps such as De Ashi Barai. This, however, provides a limited vocabulary.
Poka Yoke is the Japanese term for ‘Error Proofing’ – an approach developed by Shigeo Shingo, an industrial engineer central to the Toyota Production System. Shingo is perhaps better known for his work on set-up reduction and the Single Minute Exchange of Die (SMED) method. Apparently the original English translation was one of ‘Idiot Proofing’ or ‘Fool Proofing’, later rejected by Shingo as being too impolite. (Some texts say that the original Japanese term was Baka Yoke and this was also discarded for the same reason but this conflicts with those who talk of the problem being in the translation. As ever we can debate the origins of the terminology or what we can get on with applying a good, common-sense, approach.)
We can all see examples of error proofing in today’s manufacturing environments. The most obvious one relates to health and safety, with photo-electric cells only allowing tools to start when a guard is engaged. Production engineers have for many years been creating jigs which are asymmetrical and thus only allow components to be held in one orientation, or have switches to detect bored holes in a component before another tool is thrust into the hole for grinding the desired surface finish. Another often-quoted instance is where sensitive electrical equipment is given its own dedicated ring main where all the power sockets have one pin-hole turned through 90 to prevent spikes caused by careless people plugging in hand drills or similar equipment.
Shingo identifies three different categories of poka yoke – the contact method which confirms contact being made between a production device and the item being made, the fixed-value method based on whether a given number of physical movements have been made (for example, that a tool has been located in the required places) and the motion-step method which confirms that the defined number of process steps have been completed (such as the operator confirming that a component has been cleaned prior to an assembly operation being commenced). Within each category the poka yoke can be based either around the operation being prevented or a warning message being generated.
We thought it interesting to think of examples in our own lives. Where do we see, or use, poka yoke in action away from the workplace? Three of the team came up with these:
I suppose the thing that we all come across most on a day to day basis are hotel keys with great big chunks of metal attached. The hotels have recognised that if they make these things difficult to walk around with then there’s less chance of our walking off with them in our pockets when we leave. It’s a warning type system rather than prevention, but generally, it seems to work. The fact that it makes life awkward for people staying in a hotel for several days at a time is obviously a small price to pay – after all it’s the guests who suffer the inconvenience of these horrible lumps rather than the hotel management who gain the benefits.
Of course the credit card type electronic key is prevention-type error proofing in that the coding is changed when a guest’s departure point is reached. We can leave with a key card in our pocket but that card is no longer any use for getting anybody into the room.
I’m rather proud of a poke yoke approach to ensuring cold orange juice in our home. We’ve always kept two cartons in the ’fridge so when we reach the end of one we can continue to pour from the other. Unfortunately some family members would occasionally open the second carton and both would be almost empty at the same time. After years of saying to everyone “if the carton you pick up hasn’t been opened, then put it back and pour your drink from the other” my patience ran out and I set about error prevention.
The instruction is now “always pour your drink from the carton that isn’t upside down. If you take the last of this carton pour the rest from the other one, throw the empty carton away and take another one from the cupboard and put it into the ’fridge upside down – so that nobody opens this one until the other one is empty, by which time this one will be cold.” I was happy when two offspring recognised MLG’s approach to bringing about change for the better!
Our family has developed a way of ensuring that items needing to be posted are taken to a post box in a reasonable time, rather than spending several days sitting on a shelf waiting for someone to pick them up.
What happens is that anybody with an item to post places it on the floor against the front door. Whoever is next to leave the house takes out with them any such items and is responsible for them being posted. It’s not guaranteed because the next person to leave the house could be going somewhere by car and already be running late, meaning that stopping at a post box is not a good idea. If this is the case then that person leaves the outgoing mail for the next person to leave. This has worked for a number of years.
As you might guess, this is one of the questions we ask people when we run training on subjects like this. Where can you see error proofing in your own life?