It’s all about measurement, by Dr Neil Calder

Sometimes brief moments in time live with us for many years afterwards, echoing observations or points of realisation.  One such moment happened for me, on an evening in Brussels during one of the many stints I’ve done there as an evaluator for European Commission industrial grant proposals. 

After dinner one evening, I happened to be walking back through the city centre with another evaluator who had been a very senior and instrumental figure in the creation of the manufacturing capability for large carbon fibre composite wings. It felt like there was a road to Damascus moment when she came out with the pivotal statement: “It’s all about measurement, really.”

Had that ever actually been in question? Maybe just another case of an idea moving from the intuitive side of the brain to the logical one through verbalisation, when we hear or read something we’ve had a hunch about and think “oh, yeah, of course…I always knew that”.

We had been talking extensively that evening about ways of achieving increases in the physical and product volume scale of high-performance composites manufacturing, something into which a great deal of public money has gone in the past decade or so and with which we were both very familiar.

The consensus was on ironing out the kinks and snags in the flow of manufacturing operations and not just getting things right each time but in knowing that they were. I’d already known of the critical and pivotal part which metrology plays within the engineering and economic value flows of complex and high value manufacturing processes for some time, but it was refreshing to hear this expressed so definitively, and especially in a field like high-performance composites where it’s the layup techniques or processes or the material transformations (plasticity, polymerisation, etc.) which always to tend grab the headlines and the attention.

Viewed from one perspective, measurement comes after manufacturing process actions in order to verify and validate them and as part of a quality check veto. Viewed from another, however, it precedes and even drives them: informs them.

In an incremental process like composites layup, much as it is with additive manufacturing, it really is all about measurement, or the ability to know precisely what you’ve just done and how it matches what’s in the ply book, or STL file.

Manufacturing tolerances have a habit of stacking up, potentially against you rather than averaging out, and the ability to temper or adjust what you do in the next operation or step based on real-time measurements of the last one keeps the process on track. I recall a rather sardonic comment from the head of Rolls-Royce’s additive layer manufacturing programme regarding the development turbine casing he had produced, a large and complex metal part: “Every new layer is a fresh chance to screw it up!” I couldn’t agree more.

To paraphrase Lewis Carroll, in Alice in Wonderland: If you don’t know where you’re going then any road will take you there. In fairness, this notion was also set to music over a century later by George Harrison, but it emphasises the point that evidence-based decision making within manufacturing operations needs the numbers: the real and immediate numbers that is, not the nominal or aspirational ones, in order to avoid fumbling in the dark.

What’s the alternative? Assumption and blind faith? (Or more emotively disappointment and recrimination?) Measurement in manufacturing allows efficient evidence-based decision making and ties the present with the future, and ultimately the customer.