Poka-Yoke | What is Poka-yoke? | Mistake Proofing | Error Proofing

Poka-Yoke | What is Poka-yoke? | Mistake Proofing | Error Proofing

→ Poka-yoke means "error proofing" or "mistake proofing".
→ Poka-yoke came from the word "Poka" and "Yokeru".


What is Poka-yoke?

→ Poka-yoke is a Japanese term that means "error proofing" or "mistake proofing".
→  It is any mechanism in any process that helps for "mistake-proofing" or "error proofing".
 This word came from the word "Poka" and "Yokeru".
 Poka means "Mistakes" and Yokeru means "to avoid"
 We can eliminate product defects by Poka-yoke either preventing it, correcting it or detecting is as they occur.
→ It is one of the Lean Manufacturing Tools
 This concept was adopted, by Shigeo Shingo as part of the Toyota Production System.
 It was originally described as baka-yoke then it was changed to the poka-yoke.
 Shigeo Shingo used the word "Poka-yoke" in the 1960s for prevention of human error during industrial processes design.




Example of Poka-yoke

 A simple example is when we start a car having a manual gearbox, we must have to press on the clutch pedal before starting.
 This prevents us against the unintended movement or jerk of the car during the starting
 Seat Belt wearing Indicator.
 Auto-locking of the door at the certain speed of the car.
 Bar code for correct product identification


Example of Poka-yoke


➤ Implementation in manufacturing

 It can be implemented at any step of the manufacturing process.
 We should implement Poka-yoke, where the possibility of something can go wrong or an error can be made.
 It is a part of Lean Manufacturing

➤ Steps of Poka-yoke Implementation

  1. Identification Problems
  2. Prioritize
  3. Seek root cause
  4. Find and Implement solutions
  5. Mesure the results



Three Types of Poka-yoke for detecting and preventing errors in a process:

Shigeo Shingo recognized three types for detecting and preventing errors,

  1. The contact method
  2. The constant number (or fixed-value) method
  3. The sequence (or motion step) method

➤ [1] The contact method:

 The contact method identifies defects using a part’s shape, color, size, other physical attributes.
 It can also include limit switches and proximity sensors.

➤ [2] The constant number (or fixed-value) method:

 When certain movements are not made then the Poka-yoke inform the operator this method is known as the constant number (or fixed-value) method.
 Counters can be used for this at each step of the process as necessary.

➤ [3] The sequence (or motion step) method:

 In this method, the Poka-yoke ensure the sequence fo the process step before moving to the next step.
 This is known as the sequence (or motion step) method.
 The sequence method is not allowing the mistake to be made in the first place.
 Example of sequence method is color coding and tagging and this parameter are checked at each step before moving forward.




Guidelines for Poka-Yoke:

  1. Quality Processes
  2. Utilize a Team Environment
  3. Elimination of Errors
  4. Eliminate the Root Cause
  5. Do It Right The First Time
  6. Eliminate Non-Value Added Decisions and Activity
  7. Implement a Continual Improvement Approach

➤ [1] Quality Processes:

 Make a robust process design for zero defect manufacturing.


➤ [2] Utilize a Team Environment:

 For any improvement, brainstorm with the teams so we can use their knowledge and experience to implement our improvement.


➤ [3] Elimination of Errors:

 Use various problem-solving methodology or techniques for reducing defect and decrease defect to zero.


➤ [4] Eliminate the Root Cause:

 Eliminate the root cause of any problem by implementing poka-yoke.


➤ [5] Do It Right The First Time:

 Make the process very effective to perform functions correctly in the first time.


➤ [6] Eliminate Non-Value Added Decisions and Activity:

 Identify all non-value added decision and activity and eliminate it.


➤ [7] Implement a Continual Improvement Approach:

 We can not get 100% result in a single try.
 So, implement improvement actions immediately and focus on continual improvements so we can get a 100% result.




Six Poka-Yoke Techniques for Error Proofing

  1. Elimination
  2. Replacement
  3. Prevention
  4. Facilitation
  5. Detection
  6. Mitigation
Six Poka Yoke Techniques for error proofing


➤ [1] Elimination:

 Primarily focus on elimination
 In Elimination, we have to eliminate the step that is responsible for the mistake
 Remove Non-Value Added activities
 Redesign the product and modification of the process (as applicable)
 Examples: Replace manual data entry with barcode scanning

➤ [2] Replacement:

 If elimination is not possible the second option is Replacement.
 In Replacement, we have to replace the step with a more reliable mistake-proof one
 Automation of repetitive motion activities
 Examples: Welding Robotics for an automotive manufacturer

➤ [3] Prevention:

 If the above two methods are not possible then the 3rd option is prevention.
 Change product or process (as applicable) so that mistake is prevented.
 Prevention is a physical barrier to prevent undesired action.
 Examples: Safety guards on rides, Plugs for 110V & 220V, Printer cartridges and Go/No Go Gauges etc...

➤ [4] Facilitation:

 If the above three methods are not possible then the 4th option is facilitation.
 Facilitation is to help someone for taking the right decision.
 We can facilitate any process or product by visual controls like color coding, labels, lines,
 and signs, etc...
 Examples: Warning signs, Checklists, Traffic lane markings, Color-coded parts or tools, etc...

➤ [5] Detection:

 If the above four methods are not possible then the 5th option is facilitation.
 Detection is to identify or detect the wrong product or process immediately after it happens
 We can provide detection by Sensors, limit switches, or light sensors
 Examples: Safety guard limit switches to prevent machine running in an open condition, Computer warning if all information is not filled in

➤ [6] Mitigation:

 If the above five methods are not possible then the 6th option is mitigation.
 Mitigation is to minimize the effects of mistakes or failure.
 This method is used when the mistake cannot be eliminated
 Examples: Personal protective equipment, Airbags in cars, Electrical Fuses, and An eraser on a pencil, etc...




Benefits of poka-yoke implementation:

  • Elimination of many operations related to quality control
  • Increase the motivation of an employee
  • Reduce the overburden of operators from repetitive operations
  • A reduced number of rejects
  • Immediate action when a problem occurs
  • 100% built-in quality control.
  • Less time spent on training workers
  • Promotion of the work improvement-oriented approach



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