Delving deeper into themes related to Production Preparation Process (3P) today I’ll explain what is meant by the “5 Steps of Jidoka” mentioned number sixteen of the 16 Catch Phrases of 3P.
Fist some background on jidoka. Jidoka is a pillar of the Toyota Production System and an innovation resulting from the invention of the automatic loom by Sakichi Toyoda in 1902. The defect detection mechanism helped enable one-piece flow and multi-process handling lines, improving both quality and productivity. Jidoka is also called “autonomation”, but not to be confused with “automation”.
Broadly speaking there are two types of jidoka. The first is more general and applied to manual work as well as machine work. This includes the idea of detecting the abnormality and stopping the process to perform root cause analysis for the purpose of acting on a countermeasure. This can be applied to office work and information flow as well, when visuals are used to signal a problem so that people can “stop and fix” rather than let problems linger.
Here’s a link to an article on jidoka by Mark Rosenthal of Genie Industries, published in 2002 by the Society of Manufacturing Engineers’ online journal. It is a good article. He mentions the 4 steps of jidoka (the first type, general application). These 4 steps are for operating jidoka as a problem detection and response system. The 5 steps to building jidoka equipment are for machine process (second type, narrow application).
There’s more. Officially there are 7 steps to implementing jidoka and the 5 steps of jidoka in 3P are adapted from these. The 7 steps are a subset of the 10 steps of full automation. Confused? At this point our graphics department comes to the rescue:
The X symbols represent manual work, the O symbols represent machine work and the yellow highlight indicates jidoka has been implemented in that step. If you go beyond the yellow area of the 7 steps of “jidoka” to full automation then you have a transfter line or perhaps even “lights out” manufacturing where loading and starting are also automated through sensors between the linked machines.
Steps 2 and 7 from the chart above are missing in the 5 steps to building jidoka equipment that are used in 3P. Pokayoke (step 7 in graph above) in both manual and machine operations is addressed in other ways in the Production Preparation Process so it may have been left out as redundant. Why work holding has been left out, I don’t know. Perhaps work holding was considered a given as part of the 3P equipment design exercise known as Process At A Glance.
The “spiral up” concept was taught to me as “take it a step at a time rather than going from step 1 to 4 right away” in order to ensure that the automation was as simple and low cost as possible. There are many catalog solutions for going from step 1 to 4 that are do not support Lean manufacturing, so 3P thinking is “spiral up”. The steps are usually written as:
5. Automatic unloading
4. Automatic return to home position
3. Automatic stop
2. Automatic feed
1. Automatic processing
You have to count from the bottom to the top because you “spiral up”.
Since the Production Preparation Process is concerned with the design of production processes and production lines from an equipment standpoint with a view to ensuring the product design can be produced at the lowest cost, it makes sense that the second type of jidoka is the main focus of the 5 steps of jidoka. Certainly the first type of jidoka or the discipline of “stop and fix” is part the standard operating procedure for people working in the line also and important to 3P.
One of my favorite quotes attributed to Taiichi Ohno is “No problem discovered when stopping the line should wait longer than tomorrow morning to be fixed.” If only we could all live by these words.