Shigeo Shingo – Poka yoke, source inspection, mistake proofing and SMED

1919 – 1990

Shigeo Shingo’s work is better known than his name. His work includes; Poka yoke, source inspection, mistake proofing, SMED (single minute exchange of die) and contribution to Just In Time (JIT) production.

Shigeo Shingo’s quality teachings were successful as they were practical and action oriented.

Poka Yoke

“Poka yoke” is about stopping processes as soon as a defect occurs, identifying the defect source and preventing it from happening again. Statistical quality inspection will ultimately no longer be required, as there will be no defects to detect – “zero defects“.

Poka yoke relies on source inspection, detecting defects before they affect the production line and working to eliminate the defect cause.

Mistake Proofing

Mistake proofing is also a component of poka yoke. Shingo introduced simple devices that make it impossible to fit a part incorrectly or make it obvious when a part is missing. This means that errors are prevented at source, supporting a zero defects process.

SMED (single minute exchange of die)

Shigeo Shingo developed SMED (single minute exchange of die) techniques for quick changeovers between products. By simplifying materials, machinery, processes and skills, changeover times could be reduced from hours to minutes.

Quick changeovers meant products could be produced in small batches or even single units, with minimal disruption. This enabled Just In Time production, as pioneered by the Toyota company.

Just in Time Production

Just In Time production is about supplying the customer with what they want, exactly when they want it. Traditional manufacturing tended to large batch production as this gave economies of scale, however required large inventories of raw materials and finished goods. Orders are “pushed” through the system.

The aim of Just In Time is to minimise inventories by only producing what is required, when it is required. Orders are “pulled” through the system, triggered by a customer order. This reduces costs and waste throughout the production process.

In summary, Shigeo Shingo focused on practical differences that made immediate differences, rather than theory.

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