To take you through the process we followed a drive unit through its creation. The driver’s special double laminate is prepared for bonding using a plasma chamber; it’s a bit like sandblasting on an atomic scale. You get the kind of bond that you could never achieve with simple adhesives, by drastically increasing surface energy. This increases the bond strength by many times over.
“The plasma chamber is one of the biggest improvements we’ve made in the last couple of years to our processes,” said Martin. “We brought the process in house in the last seven months, and it’s given us another level of control over the process.”
The bonds made by the plasma chamber have been tested over time. Martin added, “You check the results of the process months later to see if the effects have worn off, and when they didn’t, you can quickly imagine the quality improvements possible.”
The materials count is impressive. “That’s ninety-nine point ninety nine percent pure copper, that’s then gold plated too.”
The spacer layer is first placed in the laser cutter, and then on to the tensile jig for bonding (technical term, meaning ‘glued’) to the diaphragm.
An exact pattern of perforations has been developed using COMSOL to get the exact running open area to maximise performance.
Then comes one of the clever bits. “You know when you pull a rubber band how you get to a point where it starts to pull and not return to its original shape,” says Martin, adding “All polymer materials are to an extent like that. What we’ve recently started doing with the film for the diaphragm is using the tensile jig to go through a cycle to pull/relax, pull/relax to get rid of some of the stretch, almost a form of work hardening, which results in a more stable film.”
The tension jig is the metal spider-like device seen in the photographs. The diaphragm is locked down and placed under tension (those spider legs help pull the diaphragm taut, and then the machine systematically tightens and loosens).