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Minimize the Collective Loss in Manufacturing and Quality Control- Poka-Yoke Technique

Mistakes happen and people believe it’s a good thing. But it is actually not a very pleasant thing when mistakes lead to monetary losses. In most of the manufacturing plants, humans do make mistakes that lead to the production of faulty/defective products. Poka-yoke, also known as Mistake Proofing, is a technique to avoid basic human errors at work. This idea originated in the 1960s by one of the IE Engineers at Toyota, Shigeo Shingo.

 

To inspect the mistakes and to correct the defects, the Poka-yoke technique was crafted. This technique ensures that the right conditions exist before a process is executed so that errors can be Prevented. Poka-yoke also implies methodologies that Eliminate the defects in the produced output.

Let us understand this with an example

In a broader sense, it is also a behavior-shaping constraint as a process step to prevent incorrect operation.

Electric sockets ensure they can only enter in a certain way or the washing machine that does not start if the door is not closed properly in order to prevent flooding. These types of automation don’t allow mistakes or incorrect operation from the start.

 

What is the need to implement this technology?

Manufacturing defective products lead to cost-failure, as well as bring a bad name to the brand. Some customers even return the whole batch of products if they find one or two defective products in the lot. If not taken care of, the use of defective products might lead to greater or fatal losses.

Poka-yoke focuses on reducing human errors like:

  • Intentional Error
  • Misunderstanding
  • Forgetfulness
  • Misidentification
  • Inexperience
  • Willful error
  • Inadvertent error
  • Slowness
  • Non-supervision
  • Surprise

And to add to the explanation, the following are the benefits if we remove or correct these human errors:

  • Reduced set-up time with reduced production time and increased quality
  • Elimination of errors with increased safety
  • Lower quality-control cost
  • Lower skill requirements and increased production flexibility
  • Increased customer loyalty and satisfaction

 

The Principles of Poka-Yoke

The mistake Proofing technique is based on 6 principles:

  • Elimination: Do not do it anymore – This states that we must eliminate the chance of error by redesigning the process or removing the unnecessary parts of the process.
  • Prevention: Avoid mistakes – Engineer the product/process in a way to avoid mistakes at all.
  • Replacement: Implement something better – This implies substituting a faulty process with a reliable one.
  • Facilitation: Ease the process of Tasks – Employ techniques that make it easier to perform the tasks of production.
  • Detection: Observe what is going wrong and act against it – Observe the errors before the mistake occurs so that we can quickly correct the problem.
  • Mitigation: Control the situation – Minimizing the effect of errors on the overall production.

Elimination, Prevention, Replacement, and Facilitation are to avoid the occurrence of mistakes. Detection and Mitigation are to minimize the effects of mistakes once they occur.

What are the methods to implement these 6 Principles?

There are three effective methods to ensure the prevention of errors and detection of mistakes:

  • Contact Method – Through this method, the deviation in shapes, sizes, dimensions, position, and other physical characteristics are kept in direct contact with the part. The Contact method is used in situations of rapid repetitions or in cases of environmental factors like critical temperature, infrequent electrical supply, dust,etc.
  • Fixed-value Method – This method employs automatic counters or optical devices to keep a track of the number of moves, rate and length of the movement.
  • Motion-step Method – This method is useful for processes where several different activities are performed sequentially by the same operator, to ensure the operator does not commit a mistake in the normal process.

In devices, Poka-Yoke can be implemented in two ways:

Good Poka-yoke devices should be inexpensive and accurate. They must be placed close to where the mistakes can occur, to provide an immediate warning to the workers to avoid mistakes. Following are the various prevention-based and detection-based Poka-yoke devices:

PREVENTION BASED 

  • Pins
  • Contoured Locators
  • Proximity or photoelectric sensors
  • Warning lights or buzzers
  • Pressure sensors
  • The vision system, etc.

DETECTION BASED

  • Electronic sensors
  • Color-coded parts/graphics
  • Contact devices like fixtures, limit switches, etc.
  • Non-contact devices like LEDs, Pressure sensors, etc.
  • Vision Systems

 

How can you implement Poka-Yoke In your Operations?

You can follow the following steps to implement this mistake-proofing technique:

  1. Identify the Operation
  2. Identify 5 HOW and WHY in which the process can fail
  3. Choose the right approach to PREVENT or DETECT those errors.
  4. Create a checklist to ensure that all the steps of manufacturing are error-proofed or not.
  5. Test the method and measure its success rate.

Poka-Yoke is the fastest way to zero defects and efficient manufacturing. I hope this article provides value to you and your business. Have a great day 🙂

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