Resonance

[Jonathon]

Hi Fella's
Iv'e just completed the build stage of my router, Its dimensions are 1500 X 1500 using wiscarver linear bearings and 5mm pitch ball screws. I'm using RTA HGD Drives at 50v 6 amps, 3.5Nm 34 frame steppers.The Y-axis uses two srews coupled to one stepper in the middle and has no problems but the X-axis Stepper is directly coupled to the lead screw. When doing an arc there is an chatter at the identical spot and same very low feed each time. Im running Mach2 and I have tried everything. I realise that this is more than likely a resonance problem , what can I do.
Jono.

[ger21]

If it's a dual shaft motor, they make dampeners to help eliminate resonance. Or increase or decrease the feedrate to avoid the resonant speed.

[Jonathon]

They have only one shaft, I have tried different feed rates but because the motor still has to slow right down when doing an arc it still does it, I thought I might change it from direct drive to a belt to isolate the vibration.

[H500]

Do your drives have a microstepping mode? That helps immensely.

[Jonathon]

The drives have Full Step , Half Step and Quarter Step , they are set on 800 steps.

[bunalmis]

Add extra friction.

[Jonathon]

Ok, so I got home keen to try all these ideas and I decided to take the motor off the screw and there you go it still does it. On all drives on every LPT output and with every motor, it still chatters. So here is the thing, It only happens at 500 steps per second within 20 steps either side.
I have only tried 1 PC and its a laptop, tomorrow I will try another PC.
Any ideas?

[ger21]

Different drives

[jcc3inc]

Sir:
There are viscous dampers made for steppers; these are meant to minimize the resonance which a stepper exhibits. You might peruse the various stepper motor companies sites to find these. Since you are working with 1/4 step, you can't go any smaller with your setup.

Regaards,
Jack C.

[Jonathon]

FIXED!!!
I wired my motors in parallel and it fixed the problem.
Thanks for the ideas guys.
Jonathon.

[H500]

Originally Posted by Jonathon FIXED!!! I wired my motors in parallel and it fixed the problem. Thanks for the ideas guys. Jonathon.

Can you explain what you mean by wired in parallel?

[Jonathon]

The stepper motors im using have 4 windings, 2 windings per phase (8 wires), the phase windings were wired in series first for high torque, But this was causing the motors to resonate at 500 hertz. So i then reconfigured the motors in parallel. Must be somthing to do with the controllers, maybe series raised the voltage too much. ?