Topic: SD4 with ballscrew for z-axis installed
After upgrading the stock SD4 z-screw right after I got the printer to a M3 slop nut by 2n2r5 I got rid of more or less all the z-axis wobble trouble. I tried the threadless ballscrew as well, but found it started to slip after some use. I'm now on the path to add auto-leveling, hopefully using piezo-electric sensors (I have a working prototype), but I were having some trouble with a small amount of backlash on the z-axis.
I then found a (really) cheap supplier of ballscrews and ballnuts on aliexpress, at 19 usd with custom end-milling. The one I ordered arrived yesterday, and I printed an adapter so that I did not need to drill new mounting holes (and thus having the trouble of aligning these exactly around the motor axle).
I would say the ballscrew is of good quality, there is absolutely no backlash whatsoever. It is reasonably smooth for the price, giving fast and accurate motion.
I've uploaded the adapter here to thingiverse: 685231
E3D v6, bowden feeding, airtripper extruder, mk8 gear.
LM8UU X & Y carriages. GT2 belts and pulleys, bearings on all axles.