POKA-YOKE

What is Poka-Yoke?

Poka Yoke (“ポカ” “ヨケ”) is a Japanese word that means Mistake Proofing or Error Proofing or “Don’t make a mistake by mistake”. Poka Yoke was conceptualized by Shingo Shingo of Japan.

A poka-yoke is any mechanism in a process that helps an equipment operator avoid mistakes or defects by preventing, correcting, or drawing attention to human errors.

Poka Yoke is a way in which we prevent mistakes from happening in any process. This means that we apply such a method in the process so that even if someone wants to make a mistake in the process, there is no mistake.

Poka Yoke | Error Proofing | Mistake Proofing

Definition of Poka Yoke
A poka-yoke is any mechanism in a process that helps an equipment operator avoid mistakes or defects by preventing, correcting, or drawing attention to human errors.

Examples of Poka Yoke: There can be many types of examples of Poka Yoke.

• When you put a data cable or pen drive in the computer, then it can be installed from one side, but it does not seem to be installed from the other side.
• A charger pin can be installed in the mobile from only one side, it does not connect by putting it from the other side.
• While welding, the welder puts glasses or fake shields on his eyes, so that he protects the eyes from the light of welding.

On an assembly line, many types of processes are being done on a product, and in that product, two holes are made in the first process, then we have to put two pins in the fixture or jig on the third process so that that part will not come in that fixture and The operator will know that the second process has not happened on this part.

History of Poka-Yoke

Poka Yoke was introduced in 1960 by Shingo Shingo of Japan in the room of the Toyota Production System. The term poka-yoke was applied in the 1960s by Shigo Shingo to industrial processes designed to prevent human errors. Initially, it was called Baka-Yoke which means Fool Proofing or Idiot Proofing which was later changed to Poka-Yoke.

Shingeo Shingo redesigned a process in which factory workers often forgot to insert a required spring into one of the switch buttons when assembling a small switch, then said to take the first two required springs and put them on the plate, Then put the spring from the plate into the switch, when a spring remains in the plate, the workers will know that they forgot to insert it and can easily correct the mistake.

The main objective of Poka Yoke is to prevent mistakes from happening.

How many types of poka-yoke are there?

Contact Method

This type of poka-yoke uses physical stops, mechanical switches, or sensors to prevent incorrect assembly or production.

Examples of Contact Method:

1. A physical stop that prevents the assembly of a part in the incorrect orientation.
2. A sensor that detects the presence of a part before a machine can start its operation.
3. A switch that detects the insertion of a part into a specific location and ensures that it is correctly positioned.

Advantages of Contact Method:

1. Simple and straightforward: The contact method is a simple and straightforward method that can be easily implemented in a manufacturing environment.
2. Low cost: This method is often relatively inexpensive to implement, as it typically involves the use of simple mechanical devices or sensors.
3. Highly effective: The contact method is highly effective in preventing errors and defects, as it physically prevents the incorrect assembly or operation of a product.

Limitations of Contact Method:

1. Limited to physical processes: The contact method is limited to physical processes and may not be suitable for processes that involve more abstract or conceptual errors.
2. Requires physical space: The use of physical stops and sensors can take up valuable space on a production line, and may not be practical in some environments.
3. May require manual intervention: Some types of contact methods may require manual intervention to correct errors, which can slow down the production process and increase the risk of human error.

Fixed-Value Method

This type of poka-yoke uses a fixed value, such as a size or a weight, to ensure that the right parts are used.

Examples of Fixed-Value Method:

1. A size or weight check of a part to ensure that it meets the required specifications.
2. A gauge or jig only allows a part with the correct dimensions to be assembled.
3. A scale that checks the weight of a product to ensure that it is within the specified range.

Advantages of the Fixed-Value Method:

1. Precise: The fixed-value method allows for precise and accurate checks of product specifications.
2. Easy to implement: This method is often simple to implement and can be incorporated into the production process with minimal disruption.
3. Cost-effective: The fixed-value method can be cost-effective, as it may not require complex equipment or a high level of technical expertise to implement.

Limitations of the Fixed-Value Method:

1. Limited to certain types of defects: The fixed-value method is limited to checking for certain types of defects, such as size and weight, and may not be effective for detecting other types of defects.
2. Inflexible: The fixed-value method is inflexible and may not be able to adapt to changes in product specifications or production processes.
3. Potential for human error: There is a potential for human error when using the fixed-value method, as operators may make mistakes in reading or interpreting the measurements.

Motion-Step Method

This type of poka-yoke uses the motion of the operator or the machine to ensure that the correct sequence of operations is followed.

Examples of Motion-Step Method:

1. A production line that requires the operator to perform a series of specific steps in a certain order, with each step triggering the next one.
2. A machine that automatically stops if an operation is performed out of sequence.
3. A process that requires the operator to insert a part in a specific orientation before the next operation can be performed.

Advantages of the Motion-Step Method:

1. Easy to understand: The motion-step method is easy to understand, as it follows a clear sequence of operations.
2. Minimizes human error: This method minimizes the potential for human error by guiding the operator through the correct sequence of steps.
3. Increases efficiency: By following a clear sequence of operations, the motion-step method can help to increase the efficiency of the production process.

Limitations of Motion-Step Method:

1. Inflexible: The motion-step method may not be flexible enough to accommodate changes in the production process or product specifications.
2. May require manual intervention: This method may require manual intervention in some situations, such as if an operation is performed out of sequence.
3. Limited to certain types of errors: The motion-step method is limited to preventing certain types of errors and may not be effective for preventing other types of defects.

Self-Checking Method

This type of poka-yoke uses the product itself to check for defects or errors.

Examples of Self-Checking Method:

1. A product that checks its own wiring or connections to ensure that they are correct.
2. A device that automatically checks its own calibration and adjusts itself as necessary.
3. A machine that performs a self-diagnostic test before starting each production cycle.

Advantages of the Self-Checking Method:

1. Reduces human error: By allowing the product or machine to check itself, the self-checking method reduces the potential for human error.
2. Increases efficiency: This method can help to increase the efficiency of the production process, as it can detect and correct errors in real time.
3. Independent verification: The self-checking method provides independent verification of the product’s quality, which can help to improve overall confidence in the quality of the finished product.

Useful Links:

• Productivity Tools
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Limitations of the Self-Checking Method:

1. Complex and costly:

Warning Method

This type of poka-yoke provides a visual or auditory warning if an error occurs.

Examples of Warning Method:

1. A machine that emits an audible or visual alarm if it detects an error or defect.
2. A process that displays a warning message if an operator attempts to perform an action that is outside of the acceptable range.
3. A product that includes a warning label or indicator if it is used in an incorrect manner.

Advantages of Warning Method:

1. Easy to implement: The warning method is often easy to implement, as it typically involves the use of simple warning indicators or alarms.
2. Cost-effective: This method can be cost-effective, as it does not typically require complex equipment or a high level of technical expertise.
3. Can be used in conjunction with other methods: The warning method can be used in conjunction with other poka-yoke methods to provide multiple layers of protection against errors and defects.

Limitations of Warning Method:

1. Relies on human intervention: The warning method relies on human intervention to correct errors, which can increase the risk of human error.
2. May not prevent errors: A warning may not prevent errors from occurring, and may simply alert the operator to a problem after it has already happened.
3. May not be effective for all types of errors: The warning method may not be effective for all types of errors, and may be less effective in detecting certain types of defects.

Different types of poka-yoke based on implementation, including:

1. Physical poka-yoke: This involves the use of physical devices or barriers to prevent errors, such as jigs, guides, or interlocks.
2. Procedural poka-yoke: This involves the use of procedures or protocols to prevent errors, such as standard operating procedures (SOPs) or checklists.
3. Information poka-yoke: This involves the use of information systems or software to prevent errors, such as error-checking algorithms or data validation rules.
4. Administrative poka-yoke: This involves the use of administrative or organizational measures to prevent errors, such as role-based access controls or cross-training programs.
5. Combined poka-yoke: This involves the use of multiple poka-yoke mechanisms, such as a combination of physical and procedural poka-yoke, to provide multiple layers of protection against errors.

How to Implement Poka-Yoke

To implement poka-yoke, you can follow these steps:

1. Identify the potential sources of error: The first step in implementing poka-yoke is to identify the potential sources of error in the production process. This may involve reviewing production records, observing the production process, or speaking with operators.
2. Choose the appropriate method: Based on the sources of error that you have identified, you can then choose the appropriate poka-yoke method to implement. There are several different types of poka-yoke methods, including contact, fixed-value, motion-step, self-checking, and warning.
3. Design and implement the poka-yoke: After selecting the appropriate poka-yoke method, the next step is to design and implement the poka-yoke. This may involve designing a new tool or device, modifying an existing one, or simply adding a warning label or indicator.
4. Train operators: It is important to train operators on the use of the poka-yoke so that they understand how to use it correctly and can detect and correct any errors that may occur.
5. Monitor and evaluate the effectiveness: Finally, you should monitor and evaluate the effectiveness of the poka-yoke, and make any necessary adjustments or improvements. This may involve tracking production data, speaking with operators, or conducting regular inspections of the production process.

Benefits of implementing Poka Yoke

• Workers have to devote less time to training.
• Implementation of various quality-related processes.
• Getting rid of operators from repetitive tasks.
• If there is a problem, take immediate action on it.
• Not reaching the defective customer.
• Quality improvement.
• Reduction in accidents.
• Increase in the morale of the workers.
• Reduction in rejection.
• Make corrections before problems arise.
• Having 100% quality control.

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