The science of perfection

In a long ago school history lesson, I was told that one factor in the victory of industrial north over agrarian south in the American Civil War lay in the interchangeability of rifle bolts. The bolt of a southern rifle, we were told, was machined to precisely fit the weapon for which it was made; a northern bolt, by contrast, was a sloppier thing, mass produced and matched randomly to other parts made to the same standards. The result, apparently, was that a Confederate soldier with a damaged bolt held a completely inoperative firearm while his Union counterpart could simply replace the damaged part. I have no idea whether or not this account was true, but it did make a point: control of accuracy in manufacturing process is a strategic issue, with a gamut of consequences to be envisaged and planned against rather than assumed.

A decade or so later, as a maths’n’stats undergraduate working graveyard shifts in a valve factory, fruit cannery or beverage bottling plant to pay my way, I learnt the economics of quality control in a vividly personal form. Any fault which escaped my attention caused a deduction from my wages; so did any losses when I mistakenly pulled a satisfactory item from the line or, worse still, stopped the line itself. There was astonishingly little science in the control of production quality, however. Canned fruit was assessed by eye (through a foggy Pyrex window) before the lid went on. Even in an armaments factory, randomised sampling meant pulling a component from the output box when I happened to feel like it and subjecting it to a crude ‘go, no go’ gauge.

Fast forward to 2008, and huge strides have been made in some ways, but remarkably little in others. We now have industries controlling production quality to tolerances that would have been unthinkable at that time, and others at a level that would not have taxed the manufacturing capabilities of the late 18th century.

Nor is the division always between large, wellresourced organisations and small ones on a tight budget. [read more...]