Poka-Yoke

Poka-yoke is a mechanism used to eliminate the error by effectively making it impossible to make mistake in a given process.

  • Poka-Yoke is a Japanese term that means "Mistake Proofing". Poka-yoke is in Lean manufacturing is a mechanism that helps an equipment operator avoid(Yokeru) mistake (Poka)

  • Poka-yoke is adopted by "Dr. Shigeo Shingo" as a part of the Toyota Production System in 1960.

  • It was originally described as "baka-yoke" but as this means "Fool proofing" the name was changed to the Poka-yoke.

  • It is one of the Lean manufacturing tools .

Objective of Poka-yoke

  • The main objective of poka-yoke is a "Zero defect"

  • build quality into the process through early detection & Prevention of defect

Need of Poka-yoke

  • For any manufacturing industry defect or error are always the key concern, and the success of any organization depends on the quality of the product.

  • Poka-yoke is one of the presentations of "good kaizen" or superior continual improvement because of its prevention nature.

  • Poka-yoke device is any mechanism or idea that either avoids the mistake from being made or makes the mistake easily detected at a glance.

  • Shingo states, "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".

  • It is therefore an effective approach to apply mechanisms to prevent error formation precisely at the moment they occur.

When to use it

Poka-yoke can be used whenever something goes wrong or an error made


the error can be any of the following

  • Processing error

  • wrong parts

  • Missing of operation

  • Damaged material

  • Human error

  • Information missing

  • Inappropriate procedure

Step of poka-yoke implementation

  • Identify the problem

  • Analyze and understand the way in which the process can fail.

  • Decide the right poka-yoke approach

→Shut down type

→Attention type

  • Determine the required type of poka-yoke

→Contact Method

→Constant Number or Counting Method

→Motion-Sequence Method

  • Check effectiveness

  • Train the operator, review performance, and measure success.

Types of poka-yoke

There are three methods of detecting and preventing Poka-yoke

1-Contact Method

2-Counting Method

3-Motion-Sequence Method


Contact Method

  • These can be as simple as guide pins or blocks that do not allow parts to be seated in the wrong position prior to processing.

  • it can also include a limit switch and proximate sensor that signals to the operator right away that something happening wrong.

Counting Method

  • It is used when a fixed number of operations are required within a process, or when a product has a fixed number of parts that are attached to it.

  • A sensor counts the number of times a part is used or a process is completed and releases the part only when the right time is reached.

Motion-Sequence Method

  • This method ensures the sequence of operation step before moving to the next process

  • This method uses sensors and photoelectric devices connected to a timer. If the movement does not occur when required, the switch signals to stop the process or warn the operator

Poka-Yoke System for Mistake Proofing

1. Awareness

(Brainstorming, Communication, Measurement)

2. Root Cause Analysis

(The Five Why’s, Brainstorm & Prioritize Causes)

3. Six Poka-Yoke Techniques

1. Elimination

2. Replacement

3. Prevention

4. Facilitation

5. Detection

6. Mitigation



The Six Mistake-Proofing Techniques


1-Elimination

→Eliminate the step that causes the mistake

→Remove Non-Value Added activities

2. Replacement

→Replace the step with a more reliable mistake-proof one

→ Automation of repetitive motion activities


3. Prevention

→Change product or process so that mistake is impossible

→Physical barrier or fit to prevent undesired action


4. Facilitation

→Make the correct action far easier than the mistake

→Visual controls like color coding, labels, lines, and signs.


5. Detection

To identify an error before further processing occurs so that the user can quickly correct the problem


6. Mitigation

→ Seek to minimize the effects of errors.


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