Peter-
Thanks so much for chiming in.
I may indeed be making assumptions that are incorrect...
A wee bit of background-
The machine is a Parker Majestic CNC ID grinder that I have converted to an OD/ID grinder.
The ballscrews are 10TPI. Original servos and drives removed.
Steppers are 900 Oz/in
steppers are geared down at the original ratio. X Axis 20 teeth on stepper and 50 teeth on ballscrew shaft. Z Axis 20 teeth on stepper and 30 teeth on ballscrew shaft.
Regardless of the intent of microstepping, as I understand it, 10x MS should fool the motor into thinking it has correct windings/magnets etc to have 2000 steps per rev. At 2000 steps per rev, the X axis motor would move .18 degrees per step. At a ratio of 2:5, the ballscrew is driven .072 degrees. 360 degrees of rotation at the ballscrew moves the X axis .100". 360/.072deg = 5000. .100"/5000=.00002"
If my math is correct (and frankly, its always been suspect) the X axis can be moved .00002" per step.
I get that the intent may be different than you think microstepping was designed for, but all I am doing is (effectively) "electronically" gearing down the motor.
"The result of this is that microsteps are not linear between full steps, so the accuracy is not there." I am not clear on this. did you mean the steps are not linear in that they are not accurate angular movements of the shaft when microstepped? or that the holding power is not linear as it pertains to the differing holding torques available to "real" steps and their associated detents vs. those available to artificial sub steps.
If the former, then yes. that would effect accuracy. If the latter, then (as long as the holding torque is not exceeded) the motor should hold at any one of 2000 positions, thus accuracy is not compromised.
All this assumes that the machine would not exhibit any stick slip, ballscrew inacuracy, backlash, way wear or inaccuracy, no belt stretch etc. I know how machines behave in the real world vs how they move on paper.
In actuality, for a grinding machine of this type and size, little load is put on either axis. Again, assuming that you are finishing and not hogging off stock (wrong machine for that anyway) and if it holds, position, its gonna get the job done.
"The accuracy of the machine should be the distance that an axis moves for a full step" Why? if I can make the motor turn in 2000 steps, with my gearing ratio, I will get a movement of .00002" correct? that is after all the goal.
"The purpose of the G901X microstepping multiplier board is to cater for computers or systems such as PLC or Arduinos that cannot generate a high enough step rate. So you should remove the step multiplier board from the G203V." Again, regardless of the designers intent, if 10x microstepping makes a move of .00002", their intent is irrelevant to me.
"The best way to get the accuracy you need is to mechanically gear down the axis with belts so that the accuracy of a fullstep position provides the accuracy you need." Not sure I follow. The "best" way is one that works, as I intend it to. If it involves a step pulse multiplier, so be it.
FYI, I am running an Ethernet SS and a 70VDC P.S.
your thoughts?
thanks,
Nate.