Industrial Glossary

Visit Poka-Yoke is a fundamental technique in Lean Management, invented by Japanese engineer Shigeo Shingō, and used mainly in the Toyota production system (TPS). The term is made up of poka (unintentional error or absent-mindedness) and yokeru (avoid). The concept is therefore the error-proof or the prevention of unintentional errors.

In-depth definition : Poka-Yoke is the design of a process, tool or workstation so that it is impossible for the operator (or machine) to make an error. If the error cannot be avoided, the device must prevent it. detect immediately and stop the process before the fault is propagated to the downstream customer. This is an engineering principle designed to guarantee the Quality from the very first time (First Time Right), by acting on the root cause of the human or machine error, rather than simply correcting the fault.

The Three Approaches to Poka-Yoke

Poka-Yoke devices, integrated into Work Instructions and Manufacturing range, are classified according to how they handle errors:

A. Contact Method

• Principle : Uses physical shape or product characteristics (size, color, weight) to detect errors.
• Example: A mold designed to receive the part only in the correct orientation. Coding on electrical connectors to prevent incorrect connection.

B. Fixed-Value Method

• Principle : Ensures that a precise number of actions or parts has been performed or used.
• Example: An assembly device that refuses to close until the exact number of screws (defined in the Bill of materials - BOM) has not been inserted, or a machine that stops its cycle if it has not counted the correct number of strokes.

C. Motion-Step Method

• Principle : Checks that all steps in a process sequence (defined in the Manufacturing range) have been carried out in the right order.
• Example: A sensor that checks that the operator has scanned all the parts before validating the assembly and moving on to the next stage.

Poka-Yoke and Industrial Performance

The application of Poka-Yoke is a powerful lever for the’Operational Excellence and the Industrial Engineering :

1. Eliminating waste (Muda): By preventing defects, the Poka-Yoke eliminates the most costly waste: scrap, rework and unnecessary inspections, contributing to a high quality of life. Industrial Performance.
2. Flow enhancement : An error-free process is a smoother process, making it easier to set up the Pulled Flow and respect for Takt Time required.
3. Standardization and KAIZEN : Identifying the root cause of an error (via the Root Cause Analysis - RCA) leading to a Poka-Yoke is an act of’Continuous Improvement. The anti-error device is then integrated into the standard (the’Working Instructions), ensuring the durability of the improvement.
4. Operator autonomy : Poka-Yoke simplifies complex tasks, reduces the operator's mental workload (he no longer has to remember a critical control) and enables him to concentrate on higher value-added tasks.

Poka-Yoke in the Age of Industry 4.0

Visit Industrial Digitization has extended the scope of Poka-Yoke beyond mechanical devices:

• Digital Poka-Yoke: The system MES (Manufacturing Execution System) or the’ERP (Enterprise Resource Planning) can act as a Poka-Yoke, displaying an error message or blocking validation of a step if the data is incorrect or incomplete (e.g. the operator forgets to enter a critical parameter, or tries to use an obsolete version of the Manufacturing file).
• Machine Vision : The integration of Machine Vision and the’Artificial Intelligence (AI) enables the creation of sophisticated Poka-Yoke systems that check the presence, orientation and conformity of parts on the line at very high speeds, in real time.

In conclusion, the Poka-Yoke is a proactive approach to quality, based on the principle that to err is human, but that it is possible to make processes infallible. It is a must for any SME wishing to achieve world-class quality.