Error Proofing

Error proofing is needed to reduce overall cost, reduce the number of quality concerns and can be a very useful tool to reduce downtime to increase Overall Equipment Effectiveness (OEE) and improve productivity to increase First Time Through (FTT). It will be in alignment with lean manufacturing implementation, high quality manufacturing and cost reduction. Below are some techniques that will help:

Shigeo Shingo introduced the concept of poka-yoke (pronounced POH-kah YOH-kay) in 1961, when he was an industrial engineer at Toyota Motor Corporation. 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 error proofing or mistake proofing.

Mistake-Proofing means apply to the process to prevent mistakes from occurring, stop the error from further processing, warn that the error has occurred etc.

Error-Proofing means apply to design to prevent assembly errors. Examples include adding design features upside-down, backwards or reversed assembly; using snap-together features to eliminate fasteners.

Poka-Yoke is a process improvement designed to prevent a specific defect from occurring. A process improvement system that prevents personal injury, promotes job safety, prevents faulty products and prevents machine damage. Poka-yokes are mechanisms used to mistake-proof an entire process. 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.

Many people think of Poka-Yokes as limit switches, optical inspection systems, guide pins or automatic shutoffs that should be implemented by the engineering department. This is a very narrow view of Poka-Yoke. These mechanisms can be electrical, mechanical, procedural, visual, human or any other form that prevents incorrect execution of a process step. Poka-Yokes also can be implemented in areas other than production such as sales, order entry, purchasing or product development where the cost of mistakes is much higher than on the shop floor.

The reality is that defect prevention—or defect detection and removal—has widespread applications in most organizations.