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13
Nov

Implement Error Proofing System “Poka Yoke” in your factory with the help of M-Box

November 13, 2019
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Poka Yoke is a Lean Manufacturing tool that allows us to detect possible errors in the production process, prevent them and thus avoid defects in manufactured parts. Poka Yoke is usually translated as “mistake-proofing” or “inadvertent error prevention” and comes from the Japanese terms: Poka = unforeseen errors, and Yokeru = avoid.

Origin | Error and Defect | Benefits | How It Works | How to Implement | Application | Poka Yoke & M-Box

Origin of Poka Yoke

Pokayoke originated in the Toyota factory in the 1960s, when Shigeo Shingo developed them as a quality assurance tool. For Shigeo Shingo, most errors are human and from these are generated defects in the manufactured parts, so he highlighted the introduction of mechanisms and elements of error detection proactively, and thus avoid defects.

Difference between error and Defect

Defect

To understand Pokayoke, it is necessary to know the difference between error and defect.
The defect occurs when any feature of the product goes out of specification and results in its rejection.

Error

The error is any mistake or failure committed in the execution of an activity during the productive process that could generate a defect.
Therefore, the error is the cause of the defect.

Benefits of Poka Yoke

Less Errors Less Defects

Poka yoke reduces the possibility of making mistakes in the production line, which will increase the quality of the product by eliminating the defects. From this, we will have satisfied customers, and in this way, we will ensure the growth and competitiveness of the company.

Increase of Productivity

Pokayoke prevents critical decisions in the production process that depend on the memory of people. In this way, operators can engage in activities that add more value, instead of devoting their greatest effort in preventing errors.

Simple and Cost-Effective

In addition, Poka yoke is characterized as a simple and cost-effective solution, placing it at the level of prevention costs, the lowest of the quality costs, approximately 5% of the total.

How Poka Yoke Works

Poka yoke is based on the following elements

Predict the error

The idea is to develop mechanisms that generate alerts when an error occurs in the production line, thus recognizing an error that is about to occur.

Eliminate or correct the error when it occurs

The idea is to prevent the error from becoming a defect, otherwise the piece must be rejected thanks to a detection system without reaching the next operation.

The solution must be simple

The idea is to achieve mechanisms or devices that are easy to implement.

How to Implement Poka Yoke

To implement Poka yoke it is necessary, in principle, to classify the quality characteristics of the product and identify all the types of defects that can be generated. Then it will be fundamental to analyze all the information related to the defects, the statistics of each of them together with the statistics of stops and machine failures will help us to know them (origin, frequency and corrective actions).

Then, it will be necessary to perform an AMEF or Cause Effect Diagram to find the root cause of the defect. Subsequently, each step of the operation where the defect occurs is analyzed, at this time we will identify the Poka yoke opportunities.
Then, we will identify the stages of the process where the deviation has occurred. Later, we design the Poka yoke to later implement it, and finally, follow-up and improvements.

Application of Poka Yoke

Poka yoke has different applications, from productive, service, administrative process to the improvement in the usability of a product by the user. In this order of ideas there are different types of Poka yoke, depending on the situation to be improved, among them:

  • Control Type
  • Detection Type
  • Contact Method
  • Fixed-Value
  • Motion-Step Method

Poka Yoke and Production Monitoring System

Having real floor data, is essential to develop a successful Pokayoke. This information will allow us to know the defects that occur in each production process and act consistently against them.

  • Cycle time monitoring:
    Setting of a mould machine can impact the quality of the product and an operator may make an unintended error which leads to defects. With M-Box (the system knows the cycle time for each individual mould setting and compares this to realized cycle times) notifications can be generated for cycle time deviations. Poka Yoke!
  • Version control work instructions or CNC programs:
    Without using strict version control strategies for work instructions (assembly) or CNC programs (milling) a commonly made error is that the shop floor executes an outdated version of instruction or program. When using M-Box production cards, with the latest versions linked to the card, such errors and resulting defects can be ruled out.

Finally, having a reliable production monitoring system such as M-Box will provide us with the necessary data to develop a successful Pokayoke and at the same time measure their impact in favor of eliminating defects in our production line.

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