Hi Cyprian,
This line pretty much sums up how to tune stepper motors -
Do I just increase the value until the motor fails?
Yes, is the answer.
Step Response is mostly for servos running closed loop, as it shows how the closed loop responds to commanded changes. This doesn't apply to steppers, as they usually run open loop, and I think even in closed loop, it's of limited use.
Tuning steppers is simply a case of keep increasing acceleration, jerk and max speed until they start stalling, then reduce it to provide a reasonable safety margin.
It's worth mentioning, that it can be worthwhile having two seperate profiles depending on what you're doing.
If you're doing a lot of short moves i.e. routing out an intricate 2.5D shape, where maximum speed makes little difference, then you should be able to tune for higher acceleration with a lower max speed.
Whereas if you're doing lots of long moves i.e. a big router where you're cutting long continual features with lots of G0/rapid moves, where maximum speed is more important, then you can tune for less acceleration with a higher max speed.
The reasoning for this is torque from stepper motors drops quickly as speed increases, so if you accelerate at a continual rate, you'll eventually run out of torque to accelerate with, at which point the stepper stalls. By reducing maximum speed, you stay in the higher torque speed range, so you can accelerate faster upto to that lower speed.
It's all very well pushing for every last bit of speed, but if you're never using that speed, it'll be costing you far more time due to slower acceleration.
Moray
