What is Poka–Yoke (Mistake Proofing)?

Today, businesses are adopting lean production philosophy to increase production performance and efficiency. Lean thinking is a mindset that minimizes factors such as unnecessary elements, errors, costs and customer dissatisfaction in production processes. Poka-Yoke is a Lean technique developed to prevent errors. The basic idea underlying Poka-Yoke is to prevent errors caused by employee carelessness.

Definition of Poka – Yoke

Poka-Yoke is a Japanese term coined by Shigeo Shingo at Toyota. In Japanese, “Poka” means “unexpected error” and “Yoke” means “prevention”. In Turkish, it means error prevention.

Poka-Yoke is a lean production method that prevents making mistakes during manual work in production processes. Its aim is to prevent, correct or uncover human errors before they occur. Poka-Yoke consists of warning mechanisms or control mechanisms. These mechanisms prevent a job from moving to the next step until the appropriate conditions are met.

Where is Poka – Yoke Used?

  • In manual operations,
  • Where tools need to be repaired,
  • In bad positions,
  • Where production and labor costs are high,
  • Where there is mixed model production,
  • In cases where there is a special reason,
  • In service-related processes where customers may make a mistake that affects the output

What are Poka – Yoke Devices?

Poka – yoke devices ensure that errors are prevented before they occur in a process. Two different Poka – Yoke devices, “control type” and “warning type”, are used to correct errors.

Control Type

Control-type devices detect when a problem occurs and stop the process completely. This gives the opportunity to take measures to correct the problem as soon as possible. The most powerful feature of the control type approach is that it ensures that the process stops when a defect is detected and resumes after the correction has been made.

Warning Type

Warning-type devices detect that a deviation has occurred and alert the worker with audible warnings, lights, etc. In the warning type approach, the process does not shut down when the error is detected. This is the biggest difference with the control type approach.

What are the Types of Poka – Yoke?

There are three basic types of poka – yoke that prevent making mistakes in a given process:

Contact Methods

The contact method uses sensing devices to detect defects in the shape, size or color of a part. These devices are strategically positioned to interact with operators and alert them if a defect is about to occur. Sensors, switches and limit switches are used as warnings, which alarm or stop the process if an incorrect operation is being performed.

Constant Number (Fixed-Value Method)

The fixed value method ensures that processes are carried out correctly by focusing on the application of specific measurable standards or values. This method uses procedures that encourage employees to comply with predefined criteria. For example, an operator is given a box of 6 parts to complete a task. If the operator has any parts left, the product is considered defective.

The Sequence (Motion-Step) Method

Poka-Yoke systems prevent errors by checking the sequence of steps in a process. In this method, the poka yoke device detects whether each step has been performed and alerts the operator when a step has not been performed.

What are the Benefits of Poka-Yoke?

  • Prevents Errors.

The primary goal of Poka-Yoke is to prevent errors before they occur. By implementing various Poka-Yoke systems such as contact methods, constant value methods, sequence methods, etc., companies help reduce the likelihood of errors occurring on the production line. These preventive measures significantly reduce the number of defects, rework and costly errors, resulting in improved product or service quality.

  • Increased Productivity.

Poka – Yoke makes operations error-free. It ensures that the work continues without disruptions such as rework in workflows, or interruptions due to defects or errors. This increases productivity, shortens cycle times and reduces operational costs.

  • Employee Motivation Increases.

Human beings are prone to making mistakes by nature and their motivation decreases due to these mistakes. This situation decreases the success and motivation of employees and causes them to be unable to solve problems. The Poka-Yoke approach is a technique that prevents errors from occurring in the work. As the error rate decreases in business processes, the motivation of employees increases.

 

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