| What is it? |
| Poka-yoke (poh-kah yoh-keh) was coined in Japan during the 1960s by Shigeo Shingo who was one of the industrial engineers at Toyota. Shigeo Shingo is also credited with creating and formalizing Zero Quality Control (poka-yoke techniques to correct possible defects + source inspection to prevent defects equals zero quality control). The initial term was baka-yoke, which means ‘fool-proofing’. In 1963, a worker at Arakawa Body Company refused to use baka-yoke mechanisms in her work area, because of the term’s dishonorable and offensive connotation. Hence, the term was changed to poka-yoke, which means ‘mistake-proofing’ or more literally avoiding (yokeru) inadvertent errors (poka). Ideally, poka-yokes ensure that proper conditions exist before actually executing a process step, preventing defects from occurring in the first place. Where this is not possible, poka-yokes perform a detective function, eliminating defects in the process as early as possible. |
| Why is it
important? |
| Poka-yoke
helps people and processes work right the first time. Poka-yoke refers to techniques that
make it impossible to make mistakes. These techniques can drive defects out of products
and processes and substantially improve quality and reliability. It can be thought of as
an extension of FMEA. It can also be used to fine tune improvements and process designs
from six-sigma Define - Measure - Analyze - Improve - Control (DMAIC) projects. The use of
simple poka-yoke ideas and methods in product and process design can eliminate both human
and mechanical errors. Poka-yoke does not need to be costly. For instance, Toyota has an
average of 12 mistake-proofing devices at each workstation and a goal of implementing each
mistake-proofing device for under $150. |
| When to use it? |
Poka-yoke
can be used wherever something can go wrong or an error can be made. It is a technique, a
tool that can be applied to any type of process be it in manufacturing or the service
industry. Errors are many types -
| 1 |
Processing
error
Process operation missed or not performed per the standard operating procedure. |
| 2 |
Setup error
Using the wrong tooling or setting machine adjustments incorrectly. |
| 3 |
Missing
part
Not all parts included in the assembly, welding, or other processes. |
| 4 |
Improper
part/item
Wrong part used in the process. |
| 5 |
Operations
error
Carrying out an operation incorrectly; having the incorrect version of the specification.
|
| 6 |
Measurement
error
Errors in machine adjustment, test measurement or dimensions of a part coming in from a
supplier. |
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| How to use it? |
Step by step process in applying
poka-yoke:
| 1 |
Identify the operation or process - based on a
pareto. |
| 2 |
Analyze the 5-whys and understand the ways a
process can fail. |
| 3 |
Decide the right poka-yoke approach, such as
using a
| shut out type
(preventing an error being made), or an |
| attention type
(highlighting that an error has been made) poka-yoke |
| take a more
comprehensive approach instead of merely thinking of poka-yokes as limit switches, or
automatic shutoffs |
| a poka-yoke can be
electrical, mechanical, procedural, visual, human or any other form that prevents
incorrect execution of a process step |
|
| 4 |
Determine whether a
| contact - use of shape,
size or other physical attributes for detection, |
| constant number - error
triggered if a certain number of actions are not made |
sequence method - use
of a checklist to ensure completing all process steps
is appropriate |
|
| 5 |
Trial the method and see if it works |
| 6 |
Train the operator, review performance and
measure success. |
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| Food for Thought ! |
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