On Fridays I will post a Lean related Quote. Throughout our lifetimes many people touch our lives and leave us with words of wisdom. These can both be a source of new learning and also a point to pause and reflect upon lessons we have learned. Within Lean active learning is an important aspect on this journey because without learning we can not improve.
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"The causes of defects lie in worker errors, and defects are the results of neglecting those errors. It follows that mistakes will not turn into defects if worker errors are discovered and eliminated beforehand" - Shiego Shingo, 1986
Instead of simply inspecting for mistakes and eliminating bad parts or using SPC to improve the processes, a different approach is to use devices or designs that will help to prevent mistakes in the first place. This approach of trying to make it difficult for the worker to make mistakes is called poka-yoke and is credited to Shigeo Shingo.
A poka-yoke device is any mechanism that either prevents a mistake from being made or makes the mistake obvious at a glance. Poka-yoke is Japanese for mistake-proofing. These devices are used either to prevent the special causes that result in defects or to inexpensively inspect each item that is produced to determine whether it is acceptable or defective.
Everyday poka-yoke examples are all around us in our daily lives. We benefit from mistake-proofing everyday whether we are aware of it or not.
Poka-yoke can be implemented at any step of a manufacturing process where something can go wrong or an error can be made. Shigeo Shingo recognized three types of poka-yoke for detecting and preventing errors in a mass production system:
1.The contact method identifies product defects by testing the product's shape, size, color, or other physical attributes.
2.The fixed-value (or constant number) method alerts the operator if a certain number of movements are not made.
3.The motion-step (or sequence) method determines whether the prescribed steps of the process have been followed.
Shingo argued that errors are inevitable in any manufacturing process, but that if appropriate poka-yokes are implemented, then mistakes can be caught quickly and prevented from resulting in defects. By eliminating defects at the source, the cost of mistakes within a company is reduced.
John Grout offers mistake proofing help for those who want to learn more. John is a Shingo Prize winning author and researcher on the human side of mistake proofing. If you already think you know something about mistake proofing then test your knowledge with this quiz.
Don't allow defects to occur in your processes by neglecting to prevent mistakes in your work. Use poka-yoke to make the work easier and mistake proof your process.
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