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Always Be Unhappy (About Quality) April 4, 2012

Posted by Tim Rodgers in Process engineering, Quality, Supply chain.
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A couple of years ago I presented a factory quality department review to the senior managers in our business group in Shenzhen. At the end of the presentation I was asked to give a summary analysis of the current status and near-term outlook for our quality metrics. I said I was dissatisfied and unhappy with the quality of our finished products and our quality systems generally, and that I would probably never be satisfied and I would always be unhappy. I saw a lot of confused expressions from the audience. I wasn’t sure anyone understood what I was trying to say, so I added: “Being unhappy about quality is part of my job description.”

It’s not enough to meet some assigned quality goal, celebrate, and then sit back and wait until the next fire breaks out. You shouldn’t be satisfied or comfortable if the percent of products conforming to specifications exceeds any target that’s less than 100%. Any part or product that fails to meet specifications requires some kind of extra handling and disposition (customer returns, scrap, or rework/repair and re-test). Regardless, it reduces overall productivity and adds avoidable costs.

Even if 100% of the parts or products meet specifications, there’s value in reducing variability. Genichi Taguchi’s loss functions and cost-of-use model illustrate the benefit to downstream customers of that part or product. In the factory in China we often encountered tolerance stacks that exceeded the top-level assembly design margin. Each of the parts were in-spec, but the cumulative effect of part variability led to a significant number of product failures.

Even if 100% of the parts or products meet specifications, you have to be concerned about whether or not the factory processes are operating within statistical control limits, otherwise you cannot predict the future performance of the processes, and you cannot be confident that you can continue building good parts or products.  You still can’t be satisfied when processes are in-control. A process in-control is in an unnatural state and will surely drift out-of-control at some point due to special causes (or entropy), requiring vigilant monitoring.

Continuous improvement means there will always be something else to work on. At some point there may be a discussion about diminishing returns and opportunity costs for further improvement, but that discussion should lead to a re-assignment of resources to the next item on the Pareto chart.

I admit I was being a bit dramatic about “always being unhappy” to emphasize my point, and you should certainly celebrate progress and intermediate goals, but you can’t be complacent about quality.

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