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: 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.
How to use:
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.
A poka-yoke device is one that prevents incorrect parts from being made or assembled, or easily identifies a flaw or error.
Or “mistake-proofing,” – a means of providing a visual or other signal to indicate a characteristic state. Often referred to as “error-proofing,” poka-yoke is actually the first step in truly error-proofing a system. Error-proofing is a manufacturing technique of preventing errors by designing the manufacturing process, equipment, and tools so that an operation literally cannot be performed incorrectly.
To avoid (yokeru) inadvertent errors (poka).