Poka-yoke

What is Poka-yoke?

Poka-yoke (ポカヨケ), translated as "error-proofing," is a system that aims to reduce the possibility of human error to zero. It is a part of the Toyota Production System.

Purpose of Poka-yoke

Poka-yoke was developed in the 1960s as a measure to prevent errors in production. Shigeo Shingo, a Japanese engineer and the father of the Toyota Production System, is considered its author. The purpose of poka-yoke is to design a process or product in a way that operators can perform each step correctly without any errors.

Currently, the poka-yoke system is used not only in the industrial sector but also in daily life. Examples include the design of 230V sockets, USB ports, or Apple's Lightning port. Nevertheless, its most significant application remains in production, where it is emphasized during the product or process design phase. By preventing the possibility of making errors during operations, the production process becomes more robust, reducing losses caused by defective products or the need for post-production repairs.

Practical Implementation

Poka-yoke solutions can be applied to existing processes or products, but they are most effective when incorporated into the design phase. To develop poka-yoke solutions, it is necessary to identify potential failure modes, which can be done, for instance, through FMEA (Failure Modes and Effects Analysis). Weak points in the design can then be addressed with poka-yoke measures. Eliminating the possibility of failure during the design phase is much more cost-effective than rectifying errors in existing processes or approved products.

A fundamental requirement for poka-yoke solutions is the complete elimination of the possibility of error occurrence.

Poka-yoke solutions are divided into two types:

• Physically preventing errors: The design allows the operation to be performed in any way, and the result is always correct, or there is a physical barrier preventing the execution of the incorrect procedure.
• Preventing the following operation: The current operation cannot be completed until it has been performed correctly, and it informs the operator that the operation is incomplete (the process step cannot be completed until all the required conditions are met, for example, all parts are in their proper positions). However, this solution must also be safeguarded against the possibility of omitting the current operation.

The second type is referred to as control poka-yoke. While the first method - physical prevention of errors, is easily understandable, the second approach often leads to quasi-poka-yoke solutions, such as using sensors for monitoring. Such solutions, while robust, do not fully meet the condition of 100% error elimination since sensors can also fail like any other devices. Relying on such solutions as 100% effective can be risky.

How We Can Help

Poka-yoke solutions are integral to TPS (Toyota Production System) and Lean manufacturing. Relevant training programs can be found in our training catalogs.

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