As part of coaching a student (and his father!) on their incredibly ambitious build-a-plotter-from-scratch project, I suggested
stealing using HP’s grit-wheel paper drive, rather than fiddling with guide rods to move either the pen carrier or the entire paper platform. Dremel sanding drums seem about the right size and they had an 8 mm shaft harvested from a defunct printer, so a pair of mounts moves the project along:
The motor mount code is a hack job from my old NEMA17 mount and the code has a lot not to like. The bearing mount puts the bearing on the proper centerline using brute force copypasta and depends on friction to hold it in place. The two models should be integrated into the same file, the shaft centerline shouldn’t involve the printed thread width, and blah blah blah:
I had him turn the shaft adapter from an aluminum rod in the mini-lathe: he’s hooked.
The OpenSCAD source code as a GitHub Gist: