Sunday, May 19, 2024


Parallel Flexures Go Round In Circles

I had a mad idea in a hotel room a few nights back about a way of doing a parallel flexure XY axis without having to support the weight of the motors. I just had to get the idea out of my head and ended up going down to reception to beg a wad of paper to scribble on.

The big issue with the OpenFlexure design is that the motion of the axes is not truly linear but circular. This doesn't matter much for small-angle microscopy or lining optical fibres up, but it does matter to me.

In theory you can calibrate it out, but in practice without a lab-full of precision gear that's a bit awkward to do. Also the range of motion is a bit small given I need to stack photosensitive resin, the workpiece, and UV light on the printer and move the stage around between it all while dodging a probe tip.

So I've mostly been fiddling around in an effort to find out what kind of flexures work, how much motion I can get out of them before they fail, whether I can print them flat and fold them up etc. Consequently my bench looks like this:

My waste basket is full of the fails. Note the pantograph. This is a key element in combining the motion of the X and Y linear drivers without one motor having to support another. It also gives me a handy method for scaling down motion. Yes, the centre is unconstrained for rotation, but I plan on having an XY-constrained stage, so that'll eliminate that problem. No idea how much constraint this'll need, or accuracy will get lost in the flexures, but I'm going to suck it and see.

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