maybe this is a simple problem for someone out there...
started to build my DIY CNC router in Jan 2017, finished sometime in late summer '17, okay now it is built and control box done, very simple DM860A stepper drivers and a generic breakout board and old PC running windows 7. there are 2 RM1605 ball screws driving the Y axis and 1 for the Z and X axis all with the same pitch and all but Y axis are run on NEMA 34 motors running on 3.5 amps, the Z axis is Nema 34 5.6 amp because I thought it would be better with the heavy actuator. I started out with round linear rails and the machine ran okay but I was having a problem with the Z axis loosing - 2.5mm every time I would run a code out, and it was not consistent at 2.5, sometime it would be 1.5 mm but every project would have a problem I am using both Vectric and Fusion 360 and the machine is running on mach3. I looked for help here and it was suggested that maybe if I was using NSK or comparable square blocks and rails for a tighter tolerance. Well I went with HD20 blocks and rails( they are great ) and can you believe after fully building this machine (2 times) it is doing the same thing? is it something I am doing wrong in the mach3 software? I know that all diameter cuts are perfect , x and y locations are spot on, and testing the motors in mach3, also perfect. I have so many thing I would like to cut but I am a bit worried about wrecking good walnut and cherry stock I have planned. so if there is any advise or things to try please let me know
thank you
pat