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Work Instructions for Mistake Proofing
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B y Kiran Walimbe- Use CFT approach to Mistake proofing.
- Selection of process for Mistake proofing.
During the third phase of APQP, the CFT shall identify the processes, where, due to avoidable human errors, the rating of "Occurrence" and/or "Detection" have increased thereby increasing the RPN for the process. Poka Yoke techniques of mistake proofing are applied to these processes in order to lower the ratings of Occurrence and / or detection.
Analysis of Customer complaints also reveals activities which are in need of mistake proofing, in order to achieve 'Zero Defect' level of working. CFT will undertake application of Poka Yoke techniques to these processes.
- The selected mistake proofing technique should qualify the following criteria:
- Inexpensive.
- Based upon common sense, preferably of the operator or the 1st line employee.
- It MUST eliminate Occurrence / Detection of the problem at the source itself.
- Occurrence oriented Poka Yoke should follow the procedure as below:
A) First classify the source of 'Occurrence' as follows:- Required action is NOT performed or is performed incorrectly.
- Undesired action is exercised.
- Information essential for performing the action is mis-interpreted.
- Mistake occurs due to complexity.
B) After having classified the source, apply one of the following techniques, as appropriate, to prevent the occurrence:- Use of 100% prevention devices such as Fouling Pins, Contoured locators or templates, Proximity or Photo-electric sensors, Limit or Micro switches, Warning lights or Buzzers, Pressure transducers.
- Design to modify to ensure that in assembly the parts shall not join if aligned wrongly.Machine will not run if operators' hands or feet are not outside or if the job & tooling are not in right position.
- These techniques should be integral part of the process.The devices are placed sufficiently close to where the mistakes occur, providing fast feedback to the operator, of mistakes occurring.
- Detection oriented Poka Yoke should use one of the following techniques for ensuring 100% detection of the mistake:
- It should be autonomous inspection occurring without intervention.
- It should be 100% inspection which occurs without intervention.
- It should determine 'before the fact' whether the conditions for 100% quality exist or not.
- It should make the error visible to the operator.
- Consider supply of exactly made kits of components to the assembler, so that any balance part will signal error in assembly.
- Consider use of electronic sensors to activate warning lights or buzzers.
- Use color coded parts or graphics.
- Make use of contact devices e.g. Fixtures, Limit switches, probes or Non-contact devices e.g. LEDs, Pressure transducers etc.
- Effectiveness of the applied Poka Yoke technique should be judged after observing the performance, for a period on minimum one month.
About The Author
Kiran Walimbe graduated in Mechanical Engineering from University of Bombay in 1972, with First class. Mr. Walimbe has 30 years of experience mostly on Production floors of Indian Automotive organizations, and is presently offering Consultancy services in the areas of QS 9000 certifications, Outsourcing & business tie-ups. Mr. Walimbe can be reached via email at kiran@pn3.vsnl.net.in.
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