On Thursday 18 March 2021 18:29:50 andy pugh wrote: > On Thu, 18 Mar 2021 at 20:52, Frank Tkalcevic > > <fr...@franksworkshop.com.au> wrote: > > Is there anything special about driving these motors? > > I guess that as they are 20-step motors it is a long way between the > poles, and microstepping relies on finding an elastic equilibrium > between poles.
A lot of that can be blamed on the poor co-operation between the motor makers and the driver makers resulting in very poor mapping of the currents delivered, to the magnetic characteristics of the motor, and I have noted that the fine microstepping performance can and usually is, related to the ideal current ratios for the individual motor, due to the non-linear magnetic performance of the iron with improved performance in terms of degrees/step often obtained at less than full motor currants. But for a 20 step motor, if I needed fine results I'd gear it down to get the accuracy needed and drive the motor at no more than half step. What I have observed is that you can get decent results from a 2M542 driver at a little over half the max current, at a /8 or even /16. Swap that driver for a DM860 and its so much poorer, that there is no optimum current, even at a /32, its essentially a half step motor in terms of how far it moves for one step. And it hammers a nema34 something awful even running at a /16. I know little about the A-4988, but its predecessor, A3977 used on the 3 & 4 axis boards from another board maker isn't that good either. YMMV of coarse, a lot at times. > I think that it is often like you describe, just rather less obvious > on a 200-step motor. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
