Poka-Yoke | you can’t go wrong

Summary

Poka-Yoke: a simple idea that eliminates defects. Yes, makes it impossible to make an error. We are surrounded by Poka-Yoke kind of devices. This article explains what Poka-Yoke is and shows a few examples of Poka-Yoke devices as well as Poka-Yoke methods.

What is Poka-Yoke?

Even if you have never heard of Poka-Yoke you have certainly used more than one. Perhaps even on a daily basis. Poka-Yoke is as old as the ancient floppy disc (which can be inserted into the drive one way only), or perhaps even older.

Poka-Yoke is a device or method that prevents people from making mistakes. The word in Japanese means mistake proofing or error proofing. Originally the word Baka-Yoke or idiot proofing was used, but someone probably figured that even those of us who are not idiots make mistakes at times so now we use the word Poka-Yoke, and no reference to stupid people is made.

How to fight with defects?

The Toyota System or Lean Philosophy aims for perfection (it isn’t called Continuous Improvement by accident). In manufacturing producing sporadic defects is better than making frequent defects, but what if one defect can destroy the brand’s reputation or -  even worse – put people in danger? In any case, each defect has the potential of pushing customers away from us and closer to our competitors. Traditional management’s first response would probably be something to the effect of setting up an effective quality check department. Let’s think about it.

Quality department – do they eliminate defects?

A quality department usually operates in one of two ways. It can either check some products (for example – every 10,000th piece that leaves the production line) or every single product. The first option will definitely raise the standard of plant’s quality but it will not completely eliminate defects. The second option, checking every single piece produced or watching to make sure that every time a service is provided it is done the right way – is either very expensive or often impossible. Imagine fast food restaurant manager standing inside a restroom and making sure the staff wash their hands every single time they leave. I guess it’s possible, but who can guarantee that the manager won’t accidentally skip someone or favor some people?

Defects from Lean Perspective

Let’s look at the problem from the lean perspective. Producing a defect followed by detecting it and finally fixing it (or throwing it away) is Muda. Wouldn’t it be better just not to make the mistake in the first place? It’s not always possible, but wherever it is – let’s create a device (Poka-Yoke device) or develop some habits (Poka-Yoke method) that will simply make it impossible to make a mistake. For example – if we don’t want people to be exposed to harmful microwaves – why don’t we install a simple device in microwave ovens that automatically turns off the oven as soon as the door is opened? Or – if we don’t want to break an ATM machine – why don’t we cut one corner of a credit card to make sure there is only one way it can be inserted? If our kids keep losing that TV remote, why don’t we tape a piece of paper on the coffee table, trace the remote on it and then show the kids that this is one and only place where the remote can be placed after it’s used (this last method reduced the remote control loss rate from 3 times a day to probably once a week!)?

Here are some other examples of Poka-Yoke devices:

And here are some examples of Poka-Yoke methods:

In companies where the Toyota System is used, Poka-Yoke devices are created every week or even every day. The Kaizen idea suggests that they don’t have to be expensive and they are usually very simple. Every company, office, hospital, home, etc. where certain mistakes are not wanted, but where imperfect beings work or live, should give the idea of Poka-Yoke some thought. It might make a big difference.

Popularity: 100% [?]

Kanban | Supply Regulation Autopilot

I didn’t realize how complicated and involved the production process  for a simple car could be until I decided to take a closer look. Working with finances, and so having little idea about the production,I admit  that, at first, I did not appreciate the complexity of the responsibilities of the production manager in our car replica plant.  This changed when I value stream mapped of one of the simplest parts the company was producing – the car seat (value stream mapping is a technique used to evaluate the flow of materials needed for providing the product to a customer – a post about VSM coming up). I thought the map of the whole car production would look somewhat like the New York City subway map and so I expected that the map of the silly car seat would be more like a close up of one station with a few bus lines crossing it, etc.. After I tried to draw the map of all the parts, services, processes, etc. that go into making a simple, leather car seat with a few metal parts, one rubber and one foam part inside I realized that it would probably take me less time to draw a map of the subway system.

“How is it possible to manage purchasing all of the parts needed, the flow of the material and work in progress, etc. of the whole car?” I thought. I guess it is possible with a large team of people who know what they are doing and perhaps some good computer software designed for it. But even then – some excess inventory is necessary to make sure no worker will run out of necessary material.

There is a better way, though. Instead of an expensive and inefficient supply department or computer software you can learn about one of Toyota’s most awesome inventions which will certainly manage the whole flow of material and work-in-process for you. I am not exaggerating here – Kanban is a simple invention that takes a huge load of unnecessary frustration off of the production manager’s back so that he or she can focus on things that really require a human touch.

Obviously Kanban is a Japanese word which is composed of two words: “kan” – visual and “ban” – card. Originally Toyota’s Kanbans were cards, but a Kanban can be a box or even a square drawn on a table.

This is how simple Kanban is: You might remember from the previous post (One Piece Flow) the pen company called New Way Pens (although you will not have to have read it to understand the following example). Frank and Dorothy were two of a few employees who were making pens. Frank’s job was to watch a little dent located between his and Dorothy’s work stations. If the dent was empty, he would take a piece of wire and make a spring which would then be placed in that little dent. That little dent played the role of a person or department responsible for providing all necessary materials to the respective work stations. Here is how Frank and Dorothy’s Kanban works (now pay close attention, we are talking about something that replaced a complicated computerized system):

- If the dent, or Kanban is full (there is a spring sitting inside) no more springs are needed.

- Empty Kanban means “Dorothy needs another spring”.

Congratulations! You just successfully graduated from the Kanban 101 course! Kanban 102 doesn’t take that much longer (and there is no need for Kanban 103).

Here is another example of a Kanban. A supplier brings ink cartridges to New Way Pens every Monday and Wednesday. Instead of going to the ordering department and interrupting Bob who is in the middle of making a phone call and ordering more plastic tubes – The supplier simply goes to the production plant and finds a red box with the label “ink cartridges, 300 pieces”. He looks inside and finds it empty. He fills the Kanban with 300 cartridges, gets Dorothy’s signature and leaves.

Now, there are actually two red boxes with the “ink cartridges, 300 pieces” label on them. Both are located by Dorothy’s work station. The one that is closer to Dorothy is the box she takes the cartridges from and puts them into the plastic pens etc. The other – right behind the first one is now full of ink cartridges. Once the first box is empty – she simply switches the boxes and starts taking the cartridges out of the 2nd box. The 1st box is now empty and waiting for the supplier. The fact that the Kanban is empty simply means: “We are ordering 300 ink cartridges. Please put them here. Thanks!”.

Obviously there are other ways to set up the production system at New Way Pens. What I described above is actually not the best way I can think of but this is a simplified version. But really – Kanbans don’t get much more complicated than this.

One of the first stages of implementing the Toyota System in a production company, or in other words – leaning the company – is replacing the Mass Production system with the One Piece Flow system. Kanban is the no-brainer tool that makes it possible. Besides the fact that it is simple it also works for us on an autopilot. The principle can also be applied in other companies which are not necessarily manufacturing plants, such as  hospitals, offices, schools and many other industries.

Popularity: 16% [?]