Snap-amp stepper configuration

[BillK]

I accidentally deleted tbe configuration on one of my machines and it’s been years since I’ve messed with configuration on it. I have not been able to find a document describing the setup.
I vaguely recall that axis resolution in the trajectory planner is not as simple as just multiplying 200 steps by the ratio of the drive mechanism. Was there something to do with the number 50? Does 50 equal a full revolution on the motor instead of 200?
Are the PID settings used at all?
It looks like sometimes the axis will simulate the oscillations in a servo system. Can I make it stop this?
In manual command entry I’ve noticed that when I do a G0 it doesn’t stop very close to the destination. But if I issue slower command with a G1 it will get closer but still not exact unless there is another command following it.

[TomKerekes]

Hi BillK,

I vaguely recall that axis resolution in the trajectory planner is not as simple as just multiplying 200 steps by the ratio of the drive mechanism. Was there something to do with the number 50? Does 50 equal a full revolution on the motor instead of 200?

Yes there are 50 sinusoidal cycles per motor rev.

Are the PID settings used at all?

Not if you are running open loop.

It looks like sometimes the axis will simulate the oscillations in a servo system. Can I make it stop this?

Not sure what you mean.

it doesn’t stop very close to the destination. But if I issue slower command with a G1 it will get closer but still not exact unless there is another command following it.

Probably improperly set Accelerations or Jerks for rapids. Configure and tune the Axis before attempting to run GCode. See here.

[BillK]

I do not understand the servo turning procedures
as applied to steppers. My procedure has just been
to adjust velocity, acceleration and to a lesser extent
jerk until the motions sound smooth. What can the
graphs tell me on an open loop stepper system? Won’t
any combination of settings show perfect following?

[TomKerekes]

Hi BillK,

You are correct, without encoder feedback there is no information on how well the axis is following the commanded trajectory. The only useful thing is the plot of the theoretical commanded trajectory to help understand what is actually being tested. For example a common User mistake is to specify a velocity much higher than the axis can achieve but not realize this because the Move tested is too small of a size with too small of Acceleration and//or Jerk to move fast. Similarly with specifying too high Acceleration.