Many years ago an old mechanical engineering friend rang me up for a beer - he had a problem.
He'd just joined a company near Cambridge, whose main work was writing programs for posh NC mills - they had a 5 1/2 axis HERCO ( Swiss) one.
It did such things as cut the moulding tools for car tyres and gas turbine rotors.
But his project was rather different.
They'd somehow got a contract for device which would ( under NC control ) produce the developments for shoes out of leather for a big shoe firm called Clarkes.
Mass production shoes are cut from leather using something like a pastry cutter. A piece of thick steel plate has grooves cut into it, into which is brazed a high tensile steel strip with a sharp edge.
But these are expensive to make, and of course there are many different sizes for each design.
Clarkes wanted a system which would cut these developments at low unit cost for new designs which they'd exhibit at fashion shows etc. It wouldn't matter if it were slow.
My friend had inherited a complicated cam - driven cutter based on on a Morris 1000 camshaft . It was horrendous.
Could there be a better way?
I said ' what you need is a vibrator'
Some time before I'd picked up a small one from a skip in a company I'd been doing a contract for.
It's basically a loudspeaker coil and magnet assembly, but intead of driving a cone it drives a threaded hole in a shaft. For testing vibration resistance of electronic assemblies. Military specs insist on this.
So we went back to my place, where I soldered a Swan and Morton scalpel blade to a solder tag, and bolted it on . Then drove it with a little oscillator at 100Hz or so . a couple of watts.
Tried it on paper and carboard - fine.
My friend then tried it on his finger. Blood poured....
'Great' he said ( after few other words) ' just what I need '
He contacted Ling Dynamic , who made the device, and built a product from it.
It could cut a 5-pointed star from thick card, and the cut out bit would fit perfectly in the hole in any position.