2014: Advent Quality: Limited Edition Widgets

by on December 15, 2014

Why is an over-narrow limit bad? Why is an over-narrow limit even a meaningful concept – surely getting things more right is always better?

If you define your widgets as a particular shade of red, and you define that shade as narrowly as you can reasonably measure, what happens?

Problems crop up. These widgets are perfectly okay on all safety measures, and you can only really tell the difference in colour if you hold them next to the standard, but they’re outside the specification. What do you do? You can’t just go ahead and sell them, because they’re out of specification. You’ve promised your customers that the widgets will be within specification. It doesn’t matter how unimportant the particular trait is – if the widgets are outside of specification you can’t pass them off to your customers as sound product. You’ll have to get specific permission to ship those substandard slightly-orange widgets, and your customer will be entitled to refuse.

Now you’ve really got problems, because there’s nothing stopping this from happening again. You’ll have to introduce new process controls to keep the colour within range, you might have to switch suppliers to a more expensive paint with tighter colour matching, you have to train all your staff to pay closer attention to the colour. And the colour isn’t even important.

Don’t define your limits narrower than they need to be. It’s wasteful and expensive, and it distracts from more important requirements that really do need to be closely controlled.

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