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#10315

Jeffeb3
Participant

This is interesting. I didn’t know that. I found a very detailed page on the tubes about it:
http://www.micromo.com/microstepping-myths-and-realities

I think they are saying that if the error in position is 1/32 step, the motor will only have 4.92% of the motor’s max torque, with more torque coming with more steps.

The consequence is that if the load torque plus the motor’s friction and detent torque is greater than the incremental torque of a microstep successive microsteps will have to be realized until the accumulated torque exceeds the load torque plus the motor’s friction and detent torque.

Simply stated, taking a microstep does not mean the motor will actually move! And if reversing direction is desired a whopping number of microsteps may be needed before movement occurs. That’s because the motor shaft torque must be decremented from whatever positive value it has to a negative value that will have sufficient torque to cause motion in the negative direction.

I’m don’t think that this means the CNC will move more with lower stepping, because it seems possible, and totally intuitive that if the motor was moved by 1/32nd of a full step, then it would be applying 4.92%, but if the deflection was greater, say 1/16th of a step, then the torque resisting it would go up to 9.8%, so in the end, you’re really not getting less deflection, but it means that 1/32nd stepping isn’t really giving you that much more accuracy. In fact, that’s in the equation for Tn. The term N/uPFS is going to either be 1/16 or 2/32 when you are trying to move by the same distance in either stepping mode. Do you read that the same way I do?

I’d rather see some experimental testing. I’m not sure a good way to do that would be. Maybe it’s as simple as changing to 1/16th or 1/8th and using a force gauge/deflection measurement? Do you have to do the experiment at different offsets from the full step, I wonder?