Need Help!- Stepper whirrs under no or little load

[cablood]

I am running stepper motors from the KL-8056D unit with the KL- 6520 power supply controlled through a C35 - QUICK SETUP BREAKOUT BOARD running off of a SmoothStepper USB Motion Control Interface for Mach 3 running Mach3 software.
When the motor (1350oz) has a load on it, it runs fine, BUT with out a load on the motor it will not. Sometimes it turns and sometimes it freezes (whirrs). It cannot be tuned, it does this at all settings. Even with a light load I have this issue.
I have also tried a 820oz motor and it does the same thing.
This motor is turning a 60 inch ACME screw horizontally with a 40 lb load on the screw and fails to turn as described above.
It works fine with a set up where it turns two 60 inch screws with a 140lb load
Do you have any idea what is going on with this issue?

[cablood]

The proper term is STALLS not whirrs. Sorry.

[vger]

What pitch is your acme? How fast are you trying to run? What settings have you tried in Mach3?

Steve

[James Newton]

Classic resonance problem. Add a damper or try a higher microstepping mode.

[cablood]

The ACME is 5 per in. I'm trying to run 200 in/min.
I tried to run full step through 16 micro step with the same effect.
Mach 3 is set to 35khz
Tuning set to:
3ms pulse
12 ramp up
8000 pp
200 in/min

And I have tried a number of other settings

Add a damper? how? what?

[vger]

cablood,

There are different types of dampers. Some have a hub surrounded by a ring that is elasticly coupled to the hub. A steppers rotary motion on each step will overshoot due to the intertia of the rotor and attached rotating mass (screw) and "ring" back and forth a little bit at the systems naturally resonant frequency. At some critical frequency (step rate) the ringing builds to a point that a subsequent step actually steps the wrong direction and additional steps then step back and forth in a stalled condition.

One person on the forum found that a hocky puck attached to the shaft cured his problem. Another uses a disk assembly that has several holes near the edge into which are small rollers with cover plates to contain the little rollers. Another used screws extending radially from a hub with loose washers on the screws (a bit noisy I think).

Steve

[cablood]

I think I'll try the disk device with ballbearings in pockets and see if that works at all.

Do you know if the GECKO controlers resolve this issue?