JIDOKA: the concept

mayo 10, 2010

JIDOKA: automation with human intelligence (Autonomation)

Jidoka is a Japanese term used for autonomation and being widely used in Toyota Production System (TPS), Lean Manufacturing and Total Productive Maintenance (TPM).  Concept is to authorize the machine operator and in any case if a problem occurs on flow line, operator can stop the flow line. Ultimately defective pieces will not move to the next station. This concept minimizes the production of wasted defects, over production and minimizes wastes. Also its focus is to understand the causes of problems and then taking preventive measures to reduce them.

History of Jidoka is back in early 1900’s, when first loom was stopped due to breakage of thread. This loom was developed by Toyota, and it stops working immediately, if any thread broken.   Taiichi Ohno is considered to be the inventor of this idea and he describes this tool as one pillar of TPS. Shigeo Shingo called it as pre-automation.

The concept of automated line is being used to relieve workers and minimize human related errors. If machine detects any defect or problem, it should stop immediately. The common causes of defect are:

  1. Inappropriate operating procedures
  2. Excessive variation in operations
  3. Defective raw material
  4. Human or Machine error

Jidoka concept was developed due to many reasons, the common reasons are:

  1. Overproduction of goods
  2. Wasted time during manufacturing at the machine
  3. Wastage of time during transportation of defected material from one place to other
  4. Waste of time during defective piece re-processing
  5. Waste of inventory

The purpose of Jidoka implementation is to diagnose the defect immediately and correct it accordingly. Now, human related judgment of component quality is minimized and worker will be only attentive, when machine will be stopped. This concept also helps in sequential inspection of components and ultimately good quality products are produced and also not much burden of final inspection is put on the shoulders of worker. Inspection is carried out by machine and when machine stops working, designated person or skilled person rush towards machine and try to resolve the problem. Jidoka focuses to investigate the root cause of that problem and make necessary arrangements so that this defect may not occur again. Defect prevention can be achieved by using Poka Yoke technique.

Jidoka is being effectively used in TPM, Lean Manufacturing and providing substantial benefits to the organizations. Common benefits obtained by its implementation are:

  1. Helps in detection of  problem at earlier stages
  2. It helps in becoming world class organization
  3. Human intelligence is integrated into automated machinery
  4. Defect free products are produced
  5. Enhances substantial improvement in productivity of the organization

When utilizing Jidoka philosophy, Taiichi Ohno had some specific goals of this tool in mind. But with the advancement in its scope, following goals are being achieved through its application:

  1. Effective  utilization of manpower
  2. Product produced will be of top quality
  3. Shorter delivery time of products
  4. Reduction in equipment failure rate
  5. Improve level of customer satisfaction
  6. Increase quality of final product
  7. Lower costs (Internal, External, and Appraisal cost etc.)

video: jidoka concept.

                         http://www.youtube.com/watch?v=3qZAb-ixOaU

           http://www.youtube.com/watch?v=JSQ0WfY86k0&feature=related

Jidoka is also called “autonomation”, but not to be confused with “automation”.

Mark Rosenthal of Genie Industries, published in 2002 by the Society of Manufacturing Engineers’ online journal. 

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.

ref: Oskar Olofsson, 2009 – Jon Miller (May 4, 2006 09:18 PM) – Society of Manufacturing Engineers’ online journal

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