TODAY, THIS CONCEPT IS IN WIDE USE IN JAPAN .TOYOTA MOTOR CORPORATION, WHOSE PRODUCTION SYSTEM SHINGO HELPED DESIGN, AVERAGES TWELVE POKA-YOKE DEVICES PER MACHINE IN THEIR MANUFACTURING PLANTS, THUS VALIDATING THE CONCEPT AS BENEFICIAL TO INDUSTRY.
POTENTIAL BENEFITS OF POKA YOKE SETUP ARE
- Elimination of set-up errors and improved quality Production capacity
- Simplified and improved housekeeping
- Increased safety
- Lower costs
- Lower skill requirements
- Increased production flexibility
- Improved operator attitudes.
- Checking systems to ensure all component are present or not before dispatch
- Checking of all components to ensure proper locations & Orientations
- Checking of components with Base Material & Colors
- LED Displays that monitor presence/absence of child components in fianl assembly
- Operations with Two hand safety
- Interlock for component rejections
- OK / Dot Hot punch for passed component
- Component tracking system with bar code and/or color stickers
Poka-yoke is based on prediction and detection. That is, recognizing that a defect is about to occur or recognizing that a defect has occurred. Consequently, there are two basic types of poka-yoke systems. The control poka-yoke does not allow a process to begin or continue after an error has occurred. It takes the response to a specific type of error out of the hands of the operator. For example, a fixture on a machine may be equipped with a sensing device that will not allow the process to continue unless the part is properly inserted. A 3.5-inch floppy disk will not work if inserted backwards or upside down. As a matter of fact, it won’t fit into the drive at all unless properly inserted. A second type of poka-yoke provides some type of warning when an error occurs. This does not prevent the error, but immediately stops the process when an error is detected. This type of poka-yoke is useful for mass production environments with rapid processing as the device prevents mass production of scrapped material. For environments where large losses of time or resources do not result, a warning poka- yoke is warranted. All that is needed is a way to ensure that the error is investigated and corrected in a timely manner.
Poka-yokes can be as simple as a steel pin on a fixture that keeps incorrectly placed parts from fitting properly, or they can be as complex as a fuzzy logic neural network used to automatically detect tool breakage and immediately stop the machine. Surprisingly, the simple low-cost devices tend to be in the majority. Regardless of degree of simplicity, all poka-yokes fall into one of three categories: contact methods, fixed-value methods, and motion-step methods. Each is briefly discussed.