Guest blogger "OU Professor ('Doman On Lean' Blog)"
When you combine JIT -> Pull System -> Kanbans and Jidoka, now you have the superhighway of the Toyota Production System and the fundamentals of the lean system.
Taiichi Ohno called Jidoka “autonomation—automation with a human touch”. Jidoka implicitly recognizes that people make errors, but rejects the idea that zero defects are impossible.
Human beings make mistakes. It is a proven fact that even the most careful, conscientious workers will make errors on the job. Lean companies accept that fact and then they build a comprehensive system where errors are either prevented or detected before they turn into defects that reach the customer.
How do Lean companies do it?
First of all, as I explained in previous blogs, the best Lean companies design the workplace to be highly visual so that everyone from the president walking through the plant to the team member doing the job can tell at a glance what is happening and what should be happening. They use the 5S tool to get there.
Remember, if you can’t see it, you can’t fix it.
The take-off point for jidoka is the identification of errors or problems. It’s alright to identify errors, even your own….so long as you stop the machine, the process or the operation and fix the problem or notify your group leader that there is a problem. Pull the andon cord and stop the line so that no defects get to the customer. Let the team help fix the problem.
Machines at Lean companies have automatic shut-offs. This means a worker can “run” more than one machine at a time. It also means that problems are quickly identified and then fixed right away by trained, committed employees so additional defects cannot be produced. Jidoka means not pushing a problem down the line to be resolved later in the repair area or worse on the customer’s premises.
The best Lean Companies do in-depth analyses of every defect that is ever created. They just don’t fix the immediate problem and keep going. They investigate the root cause and install a countermeasure to prevent it from ever happening again.
Lean also invests heavily in preventing errors through poka-yokes.
What are poka-yokes?
Poka-yokes are simple, inexpensive measures or devices that detect that an error has occurred or is about to occur. They can be implemented at any stage of a manufacturing or service process where errors can be made. Poka-yokes provide a warning before the defect occurs or automatically shuts down the machine or process and won’t let an error produce a defect that could get to the customer.
They make 100% inspection practical and affordable, especially with today’s sensor and bar code technology. As many of you know, you can be very creative with sensor technology whether they are contact or noncontact devices.
You have seen many simple poka-yokes in your day-to-day living that you probably don’t recognize. For example, the Microsoft Word program I am using to write this blog automatically corrects many of my typos while I am typing. If I make a spelling error, a red squiggly line under the words alerts me to a possible error.
Some of the best poka-yokes are the simplest. Try throwing away the plastic basket at a Potbelly restaurant. You can’t. It’s too big for the hole in the garbage can. I know because I tried to stuff it in there.
If you were absent-minded at the gas pump and tried to use the diesel nozzle, you found out pretty quickly that the nozzle was too big to get into your gasoline tank. Rumble strips on the side of the highway immediately let you know that you are drifting off the road.
All these pieces of the lean system—JIT, Pull, Kanbans, Jidoka, Poka-Yokes—combined with teams of trained, committed employees fit together to identify and solve problems before they reach the customer. You can see how the different versions of the House of Lean stack up, but are really the same.
That’s how Lean companies produce the highest quality at the lowest cost with the shortest lead time for their customers. They love finding problems because they have a system and employees trained and ready to fix them fast.