Sunday, September 21, 2025
Comparing V0.04 and Pantograph Axis Drivers
As the probe tip is shot to heck, I have little compunction about dragging it over the slide. So before I replaced it I thought I'd do a little test. I simply drew an X=Y line from (-2000,-2000) to (1500,1500) μm. The X axis is driven with the Pantograph Driver, the Y with the V0.03/4 driver. The track makes for interesting viewing.
This shows that towards the extremes of the Y axis the drive is oscillating to the point where sometimes it is going backwards! However there is a small patch in the middle that is reasonably linear, and that's my actual work area.
The X axis is demonstrating reasonable linearity throughout. There's a bit of a curve, and I suspect that's our stage rotation issue rearing its head - and I'm confident of reducing that significantly in V0.05
My hypothesis here is that as the Y axis is driven by a pivoting arm, and that at the extremes of travel the horizontal distance between the Drive Screw and the arm's pivot is reduced. This then forces the drive screw out of alignment and the wobbling begins. The X axis does not suffer from this as it is linear rather than rotational and the horizontal distance between the central pivot linkages and the Drive Screw does not change (I hope).
To test this, and simultaneously end up with a machine that works better, I suspect the most productive thing to do would be to fit the Y axis with a Pantograph Driver. The problem here is that the Z axis suffers from exactly the same problem and I would be tempted to replace that as well, which would delay resin experiments.
So I shall restrain myself and only do the Y axis, try some resin stuff, and if that's unhappy replace the Z axis as well. This is all possible now due to the presence of a limit switch on the Pantograph Driver. This is much easier to fiddle with than the one on the V0.03/4 Driver and I'll probably incorporate it in the final design.
Hmm, that's a bit of a warts-and-all shot under the workbench. Anyway, please remember that I've only got a day before surgery (don't worry about it) and may not be able to do much for a week afterwards if things are not as straightforward as expected. Here's hoping all goes to the original plan.
