Podcast: Quality Words from Dr. Deming: Cease Dependency on Inspection

Cease dependence on inspection to achieve quality. Eliminate the need for inspection on a mass basis by building quality into the product in the first place.—  Dr. W. Edwards Deming’s third point for management transformation.

You want to be a quality manufacturer? Build a manufacturing process that assures a quality build from the start, said Dr. Deming in his third of 14 points for management transformation. After-the-fact inspection doesn’t assure quality. In the best of scenarios, it only means that you catch a mistake that already has transformed into a defective part. In the more likely case, defective parts are reaching your customers.

In this episode of Behind the Curtain: Adventures in Continuous Improvement, podcast hosts Dr. Mohamed Saleh and John Dyer focus on Deming’s call for built-in quality, sharing examples from the workplace and discussing the benefits of poka-yoke, also known as error-proofing. This episode continues their exploration of Dr. Deming’s 14 points for management.

Dyer discusses ineffective inspection practices from his days at General Electric’s appliances division and cites a report that suggests 100% inspection of products is only 75% effective, “meaning that 25% of the defects will get missed.”

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Both Dyer and Saleh share the downsides of layering multiple inspections. While it seemingly should help, it instead presents opportunities to overlook an increasing number, rather than fewer, defects as each inspector believes their counterpart will or has caught defects.

As Saleh notes: “Quality is someone else's job now.”

A better solution, the hosts suggest, is to completely eliminate the ability to manufacture a bad part or create a bad outcome. In other words: Error-proof (or poka-yoke) the system. Saleh shares a story of Toyota building a Camry in which the trunk would not lock if the keys were inside of it.

Dyer discusses what he calls the three levels of poka-yoke. They are:

Level 1: Signage that provides visual cues about how to perform the task correctly.

Level 2: Something that blocks, to an extent, the ability of the worker to perform the incorrect task.

Level 3: Redesign the process completely to remove any ability to create a bad quality product.

Levels one and two are incomplete options, while level 3 is the optimal solution. Dyer and Saleh share several examples of error-proofing examples that encompass each poka yoke type.