Poka yoke
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Poka yoke (ang. mistake proofing, error proofing) is an action or improvement to the process or product, which helps to significantly reduce the opportunity for error (human mistake) either by making it more difficult to produce a defected product during production process or by making mistake so obvious, that it will be eliminated before product leaves the factory and reaches customer.
Mistake proofing is very popular these days. It is not limited to production. There are special solutions for services, programming, car driving, etc.
Poka yoke is one of Lean manufacturing pillars, together with: Konnyaku stone, Jidoka, Hansei, Andon, Just in time, Heijunka, Kaizen, Genchi genbutsu, Nemawashi.
Who invented Poka yoke?
Poka yoke was used for the first time in 1961 in Japan. It's creator was Shingeo Shingo, engineer in Toyota. He suggested that workers, even the most involved, will make errors when they are tired or not concentrated. New solutions were intended to make errors impossible.
Poka yoke meaning for the company
Poka yoke brings many advantages to the organization:
- shorter time required for training,
- less inspection required,
- often repeated operations are less involving,
- promotion of continuous improvement
- reduction of defects
- detection direct on workplace, not later in process
Poka yoke solutions
Shingeo Shingo determined several solutions that can help workers to perform their work correctly:
- Regulatory functions
- Control methods - in case of defect, the machine is stopped. Worker has to manually remove product and start the machine.
- Warning methods - in case of defect, aural or light signal turns on, but the machine still works. The worker has to stop it manually.
- Setting functions
- Contact methods - machine has detectors that are able to detect wrong installation of element by worker, wrong colour, weight, temperature, etc.
- Fixed value methods - the defect is detected if worker didn't perform exact number of movements or didn't use exact number of elements, e.g. took too few screws from bin. This requires photocell or other utility.
- Motion step methods - detection is based on time, e.g. the element won't leave the workplace if photocell didn't noticed taking a screw from bin.
Poka yoke examples in everyday life
Nowadays, the poka yoke is widespread. Everyone meets poka yoke solutions everyday, e.g.:
Computers
Poka yoke examples
- colors of plugs correspond to colors of sockets in desktop computer
- USB plug cannot be inserted inversely
- Ethernet plug cannot be inserted into other socket
- SATA disk plug cannot be inserted inversely
No poka yoke / not full poka yoke examples
- USB plug can be inserted into ethernet socket, especially in laptops
Other examples
- SIM card in your telephone cannot be inserted inversely
- Frying pan can have temperature indicator (red dot) which signals correct working temperature
- On many roads, before tunnels special gates are installed in order to stop too high trucks
- Modern cars and modern gas stations have solutions that limit possibility of inserting wrong fuel nozzles into fuel fill
- In modern car you cannot forget fastening your seatbelt. Unless you're deaf.
- In car with automatic transmission you cannot take start engine until setting Park mode or Neutral.
No poka yoke example
- Credit card can be inserted in 4 ways into ATM machine, while only one is proper. The ATM software detects it and returns the card.
Advantages of Poka yoke
Poka yoke is a system of error-proofing that can help to improve product quality and reduce the number of errors. Here are the main advantages of poka yoke:
- Reduces the chances of human errors and mistakes, as it eliminates the possibility of incorrectly produced product, by making it more difficult to produce or making mistake so obvious, that it will be eliminated before product leaves the factory and reaches customer.
- Improves process efficiency and productivity, as it increases the consistency of the production process, reduces the number of reworks and therefore reduces the time needed to complete the job.
- Enhances customer satisfaction, as it increases the quality of the product, which is delivered to the customer.
- Increases safety, as it reduces the possibility of workers getting injured while producing the product.
- Reduces costs, as it eliminates the need to invest in expensive machinery or technologies and reduces the cost of training the staff.
Limitations of Poka yoke
Poka yoke is an effective tool for reducing human errors but there are still some limitations to its use. These limitations include:
- Cost: Implementing Poka yoke systems often requires significant investments in additional equipment, labor and resources. This can be a major barrier for small businesses and startups.
- Complexity: In some cases, the implementation of Poka yoke systems can be quite complex. This can be especially true when the process is highly automated, as the systems must be integrated into the existing workflow.
- Human Error: While Poka yoke systems can help reduce the chance of human error, they are not completely foolproof. It is still possible for human error to occur, even when the systems are in place.
- Compliance: In some cases, certain Poka yoke systems may be required for compliance with industry regulations or standards. This can add additional costs and complexity to the process.
In addition to Poka Yoke, there are several other approaches that can be used to reduce the chance of errors in the production process. These approaches include:
- Standardization – Ensuring that processes are always carried out in the same way. This helps to reduce errors by making sure everyone is following the same procedures.
- Automation – Automating processes reduces the chance of errors by removing the element of human error.
- Quality Control – Putting in place quality control systems to ensure that products meet certain standards and specifications before they are released to the customer.
- Training – Providing employees with adequate training and support to ensure they are able to do their jobs correctly.
In summary, Poka Yoke is just one of the many approaches that can be used to reduce the chance of errors in the production process. Other approaches such as standardization, automation, quality control, and training are all important in ensuring production processes run smoothly and efficiently.
References
- Shingo S. (1986) Zero Quality Control: Source Inspection and the Poka-Yoke System. Portland:Productivity Press
- Fisher M., (1999) Process improvement by poka yoke, Work Study, Vol. 48 Iss: 7, p. 264 - 266
- Dudek-Burlikowska M. (2009) The Poka-Yoke method as an improving quality tool of operations in the process, Journal of Achievements in Materials and MAnufacturing Engineering, 36(1)
Author: Slawomir Wawak
