On 2021-08-03 04:43, John Dammeyer wrote: So there are other issues before I can start on the Ball
Screw Conversion.
You might bear in mind that ballscrews which use a single nut don't have zero backlash. They do have consistent backlash over the length of the screw - until they wear, of course. They certainly have lower friction than an ACME nut, but the downside of that is that there is less frictional force to resist the tendency for a climb cut or a sharp change of direction to pull the slide through the backlash distance. Yes; backlash compensation in software can help, but tends not to completely eliminate the problem. I draw all this from my own ballscrew conversion of my own mill, some 20 years ago. If I was doing it again, I would use two nuts, with spring tension between the pair, on every axis (hindsight being a wonderful thing). I would also spend more than the considerable sum I have already spent, on higher spec ballscrews. I bought top quality screws, but not the very highest spec (the cost of which is now rather high). The upside is the machine is still holding reasonable accuracy on the climb cuts I frequently use, after all this time and a long running/cutting time.
On your off-centre problem, I agree with the comments re: mounting the work. When cutting an internal circle (for periphery or pocket), I never use a plunge cut, but always lead and ramp into the cut from the centre, for each pass. So the motion of the controlled point is always a circular arc from the centre to the wall; around the wall; then a circular arc from wall back to centre; and repeat. On a large diameter circle that involves a little more time per pass, but is kind to the cutter and the work.
Regards, Marcus _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
