What is Poka Yoke Manufacturing?
Poka Yoke is another tool in the lean manufacturing arsenal. It is a Japanese term that translates to “avoid mistakes” and the goal is to error-proof the manufacturing process. The idea behind Poka Yoke is that catching and fixing mistakes at the source prevents the production of defective products, saving valuable resources and keeping customers happier.
The term was originally coined by Shigeo Shingo of the Toyota Production System in the 1960s. After Shingo noticed that workers were regularly forgetting to place a required spring under a certain switch button, he redesigned the process to require the springs to first be placed in a placeholder and then in the switch. This way, the workers would notice if the spring remained in the placeholder and would quickly realize that they had forgotten to put it in the switch and they could fix the mistake before it was too late.
Benefits of Poka Yoke
The biggest benefit of Poka Yoke is improved quality control by preventing mistakes or catching them quickly before they can snowball into larger problems down the production line. Solving problems quickly at their source is much more time effective than having to undo the entire process and start again because of a mistake.
Other key benefits include:
- Reduced training time – preventing mistakes up front means less time needed spent on training how to fix more complicated problems.
- Continuous improvement culture – by encouraging workers to identify and solve problems immediately, a culture will develop that is focused on continuous improvement, which is ultimately good for the company’s bottom line.
- Less waste – producing fewer products with defects means less materials and resources going to waste.
- Better productivity – the entire production process will run more smoothly when mistakes and problems are prevented or solved quickly. This will result in higher productivity and efficiency overall.
Implementation of Poka Yoke Process
The recommended steps for implementation of the Poka Yoke method are as follows:
- Create a flowchart of the entire process and identify areas at greatest risk for human error.
- Identify the possible sources of each potential error.
- Come up with solutions to prevent each error. For example, eliminate or replace the step that will cause the error.
- If there is no way to completely eliminate the error, identify ways to detect and manage the error.
- Test and then implement all mistake-proofing methods.
When it comes to identifying the errors or defects, there are three main methods that can help:
- Contact method – examine the physical characteristics of the product including shape, color or size to determine whether it looks right.
- Fixed-value method – set the system to alert the operator if a particular required number of movements that are meant to be made are not met.
- Motion-step method – ensure that the required steps of a process were followed properly.
Defects can be detected by self-inspections in which the workers check their own work as soon as they have completed it; by successive inspections in which the next person on the assembly line checks the prior work; or by source inspections which are usually automatic and take place before the step, preventing the process from continuing until certain conditions are met.
Digital Poka Yoke
Digital sensors and devices combined with manufacturing software and tools are making it easier to implement Poka Yoke and ensure that production processes are error-proof. For example, processes can be automated to reduce the need for human intervention and therefore the potential for human error. And, tools like Matics can provide real-time operational intelligence that can also help stop errors before they happen.