One of the members dropped off a box of rejected 5 start lead screws. I measured the splines and 3D printed a lead nut that works with them and used it to make the elbow work. The lead nut seems to slide very well. I haven’t measured the backlash but I suspect it could be a bit tighter, or I could make a two part version with some backlash take up if more precision were needed.
The motor already had a drive pinion pressed onto it which I used as a spline by designing a coupling with matching teeth on one end and the rod thread profile on the other. Both ends are notched so they can be clamped down with a hose clamp. It seems to work pretty well. Peviously I was using a 1/4-20 threaded rod, and the motion was a bit too slow. This lead screw has 1.25 inches of travel per rev, and seems to match the other axes far better. Plus I think it looks cooler.
As before, if you like the project, please vote for me here (Paul Sisneros – Auto Barista):