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Teaching Zero Quality Control Concepts In Mechanical Engineering Technology

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1998 Annual Conference


Seattle, Washington

Publication Date

June 28, 1998

Start Date

June 28, 1998

End Date

July 1, 1998



Page Count


Page Numbers

3.539.1 - 3.539.6

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Paper Authors

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Ratan Kumar

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Bill Watt

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Session 1547


Ratan Kumar & Bill Watt Department of Engineering Technology University of North Texas Denton, TX 76203.


Zero Quality Control (ZQC) is a quality control approach for achieving zero defects. ZQC is based on the principle that defects are prevented by controlling the performance of a process so that it cannot produce defects, even when a mistake is made by the machine or a human operator. This is done by combining four basic elements1 : i)source inspection ii) 100 percent inspection iii) immediate feedback and iv) use of poka-yoke (mistake-proofing) devices. ZQC is widely gaining popularity in the industry. It is well established in Japan and its practice is catching on in USA. At the department of mechanical and manufacturing engineering technology at the University of North Texas, we strongly feel that this important tool needs to be addressed in our Quality Control class. A plan has been made to cater to this desire, and strategies have been made to incorporate it in other classes as well.


Shigeo Shingo2 is credited with starting the Zero Quality Control (ZQC) quality system. He was a leading proponent of statistical process control in Japanese manufacturing in the 1950s, but became frustrated with the statistical approach as he realized that it would never reduce product defects to zero. Statistical sampling implies that some products to go untested, with the result that some rate of defects would always reach the customer. ZQC tries to achieve zero defects in all products. This helps in maintaining customer satisfaction and loyalty, in reducing the cost associated with scrap, rework and downtime, and in attaining a company’s ability to adopt lean production methods with smaller inventories.

The majority of the defects that arise inside a factory3 originate in four Ms (Materials, Machinery, Manpower, Methods) and one I (Information). However most of the defects can be traced to the people involved in the above sources. Simple mistakes are the most common cause of defects, and they are the hardest to prevent. Since the goal of ZQC is to prevent all defects, these simple mistakes must be caught first. ZQC does not point fingers after the mistake has been made or hassles people to perform better next time. Instead it uses devices to keep errors from ever turning into defects in the first place. It talks about “mistake-proofing” the process and not “fool-proofing” it. ZQC uses control function that ensures that the necessary conditions are present to make good products.

The traditional quality improvement cycle1 is “Plan, DO, Check” (figure 1a).This cycle catches and corrects defects after they occur, but it can’t make sure that work is done according to plan

Kumar, R., & Watt, B. (1998, June), Teaching Zero Quality Control Concepts In Mechanical Engineering Technology Paper presented at 1998 Annual Conference, Seattle, Washington.

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