Wednesday, September 17, 2025
Anti-backlash And A Coupling Change
The parallelogram driver now fits together nicely, and I've added an anti-backlash mechanism with the same kind of bearing used on the old Axis Driver. The overall length is now only 20mm longer than the old one, and it has about 25mm of travel on the Drive Screw. With a ratio of 2:1 that would equate to +/-6mm of movement, all of it notionally linear. If it works, that'll be a significant improvement on the +/-2mm of movement on the old one. Updated OpenSCAD file here: https://github.com/VikOlliver/RepRapMicron/blob/main/maus/maus_parallelogram_axis_driver.scad
As you may see in the photo above, there is an anti-backlash system. There is also a drilled-out nut bearing in that red horizontal bar (which I am now naming the "Nut Bar"). Assembly is simplified too, with none of the test-fitting of the nut bearing as previously required. Movement appears smooth without binding at the extremes, but the motor has yet to have a plug fitted, so that's a bit speculative for now.
I also noticed a defect in the flexible coupling on the motor: For unknown reasons, the slicer was reducing one part of it to a single filament line and this was breaking. I've thickened it, and it's printing solidly again. No idea why that happened, but I've updated on github and printables. May explain a bit about previous coupling issues rebuilding the V0.04 machine.
Couple of things to fix: The mount puts the Drive Nut about 6mm too high on the Drive Screw, which will limit range-of-motion testing. Also itt is very difficult to access the screws that hold the motor in place - that's also a problem with the old Axis Driver. Doesn't matter for assembly, does matter for repairs and prototyping.
Guess I'd better fit that plug, now that the lash-up is worth testing. Oh, and get some more 20mm M3 screws, because I really hate mixing posidrive and slot head.
