Specs say 800 PPR, Masso set to 400.
Any practical reason for this?
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I guess no one knows.
In any case, according to Masso, you won’t get 1x resolution on MPG if the motors aren’t set to 800 PPR.
Onefinity FAQ on Masso forum:
https://forums.masso.com.au/threads/onefinity-elite-faqs.3291/#post-24139
and again here:
https://forums.masso.com.au/threads/onefinity-elite-faqs.3291/#post-24682
Just spitballin’ here, but 400 pulses each on the A and B phases would add up to 800 pulses total. That would be an odd way to write the motor specs, though.
Saw this on the Masso forum:
The setting in MASSO needs to match the setting in the driver, so if the driver requires 1600 pulse to rotate the motor one revolution, you need to tell MASSO that it requires 1600 pulses per rev.
MASSO uses the PPR and Distance per Revolution to calculate how many pulses need to be sent to move spindle the required distance. That is why you need to get DPR accurate and PPR correct.
In regards to the MPG, I’ll leave that to Peter as he has access to the equipment to test it.
Just about all the answers on their forum are provided by Peter. 
Higher steps per revolution equates to less torque, 400 was likely a compromise with the 1.2Nm stepper motors.
That sounds backwards to me, as the lower resolution, if anything, implies double the amount of rotation for the same distance. Higher rotation = faster speed = less torque.
Stepper motors are inductors, the higher the frequency the higher the impedance and therefore lower current = lower torque. Higher voltages to the driver can be used to overcome impedance at higher frequencies (I’m running at 48v in my setup) which allow for more consistent current output at higher frequencies (steps per revolution) from the stepper motor driver to the stepper motor.
Unfortunately the Masso closed loop stepper is rated for 36v max input.
As you increase the microstepping value the torque will drop, found this chart online:
I don’t know the steps per revolution on the Masso stepper but 200 is common for many stepper motors, so 400 would be 2 microsteps per step and 800 would be 4 microsteps per step.
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The Masso motors are 800 PPR according to Masso’s published specs. That doesn’t define the frequency of the pulses though, which is why I’m a little confused about the relation to torque here. WRT only PPR.
But what I’m understanding is that by using 400 (half the motor’s spec) the rps/rpm can be doubled at the same frequency. So same amount of torque but more movement than 800 setting.
When thinking about it originally I wasn’t thinking about comparing/maintaining speeds, just about resolution of movement.
That’s impossible if there is a setting for 400 pulses per revolution. I would bet it’s a 200 pulses per revolution motor (1.8 degree per step) under the covers and the lowest setting for steps/rev is using 2 microsteps.