Regardless, I have replaced the salvaged Nema 17 motors with new ones of higher torque. I've also finished the printed parts (version 1.0 anyway).
Here's a video of the first moves.
The problems mentioned in the video are being solved one by one. The print platform is now homing to the top (min) instead of the bottom. The print area size is now set correctly in the firmware, and the printhead moves to the center for a starting print.
Y-carriage racking is still to-be-solved, but I have several strategies up my sleeve.
- a new bushing on the right side (3d printed PLA bushings)
- switch to coreXY configuration, that should help.
- Redesign the Y-carriage to contain a third steel rod parallel with the upper rod. I have several extra rods, from old printers and scanners I tore down last summer.
My method for fitting PLA bushings is unique: I heat the steel rod over a camp stove, until it is hot enough to soften -but not melt- the plastic bushing. Then I shove the bushing on and work it until the fit is smooth, but zero-slop. I pull the bushing off and quench it, and the rod too. Sometimes I have to remove a little melted plastic from the rod if I got it too hot. So far, this method is working gangbusters!