My mill uses Servo Dynamics SD1525's to run all three of its axis. Originally the system was set up to receive encoder pulses from rotary encoders off the back of the servo shafts. It was found that keeping the noise away from the lines was difficult at best and random pulses would cause the servos to drift. The finish the servos would give was smooth with no faceting. The system was set to receive 40,000 pulses per inch of travel. With the rogue noise being hard to fix, I decided that magnetic scales would be the fix for that. So, magnetic scales were installed on all three axis and the rotary encoders were disconnected. These scales move at 25,400 pulses per inch, so much less counts than the rotary encoder setup. After the mod was completed, I tried out some parts and noticed that my servos would now produce a faceted finish. The interesting thing is that it does not really happen if only moving parallel to the X or y axis, but rather when making some angled move. At a 45deg movement (y=x), the faceting is at its worst. So, if one were to machine a circle on my mill, it would be seen that the quadrantal angles are the best in finish and as the angle advances toward where both servos start moving closer to an equal speed with each other (advancing toward a 45deg move) the faceting starts to show itself and become apparent. Then, once the move gets past the 45deg and begins to return to a quadrantal angle, then the faceting subsides and ultimately goes away. I can only assume this is a servo tuning issue, since I can simply jog the mill and reproduce this phenomenon without the assistance of a CNC program. if I jog in just X or Y, then there is no faceting to speak of. But, if I jog with both X and y, the faceting is there. I have never performed any servo tuning, so I am not really sure what should be done here. I can only guess that I would need to adjust the pots on the drives to fix this, but I am not sure. The one other thing I noticed is that my Y servo produces a ringing noise when it runs. This goes away once the servo is speed up to something like a rapid move, but returns when doing feed moves.