How to control quality: Err not

Is it just too obvious to say that the best way to ensure quality products go out the door is to not make errors in the first place? Perhaps. Less obvious is how to effectively design products and workflow to avoid making mistakes.

While error-proofing isn’t free, it can be considerably less costly than shipping the wrong parts, causing a shutdown, or triggering fines or remediation efforts built into some supply contracts, says David Marten, Faurecia manager of manufacturing metal engineering. “If we lose a half day’s production due to a machine being down or producing unacceptable product, we’re in big trouble. We have to do error-proofing, or we’re not going to make it as an industry,” Marten warns. He’s working with others to avoid mistakes.

Marten is on a subcommittee, Effective Error-Proofing Workgroup, under the Quality Steering Committee of Automotive Industry Action Group Forum (AIAG). Faurecia makes automotive seating in Troy, MI, and AIAG is making a guide to error-proofing; a draft is ready this month (December 2007). The guide is expected to be published by July.

The answer isn’t to automate everything, because for jobs with high variability and low number, people can be more cost effective.

“People are very good and very flexible in a lot of processes” where controls would be too rigid or robotics too expensive, says Marten. Robots are better for a lot of things, namely greater safety, fewer errors, and higher speeds, and their costs have dropped quite a bit, Marten explains, adding: “automation usually helps with error-proofing, but it doesn’t mean you eliminate operators. We just control the environment so humans have to do things right or the process shuts down.”

Does better quality control always increase costs? Not necessarily. A better question is, “How much does it cost when there’s a problem?” Keep solutions as simple as possible. Seek the most effective, least costly way to eliminate the chance of error. Ways to error-proof, Marten says, from most to least desirable, are to:

Eliminate the error-prone element;

Prevent the error;

Detect the error and prevent a defect;

Detect the defect at the source; and

Detect the defect prior to shipping.

Parts and processes should be designed so things always get assembled, labeled, packaged, and shipped correctly. If the process isn’t perfect, then errors should be caught and corrected as close to the source as possible. Appropriately placed sensors, logic, and actuators can help.

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Related stories from Control Engineering provide more information.

Quality control tips: How to avoid making errors in the first place

Includes information on costs of errors and error-proofing label-related processes.

How to improve product design

Product design gurus suggest ways to improve the processes

AIAG also provides information at its Website.

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