Dynomotion

Group: DynoMotion Message: 11867 From: lmp582002 Date: 7/6/2015
Subject: Stepper Motor Resonance

I have 4 stepper motors running on a KStep and have a huge amount of vibration at specific frequencies. I have used other stepper drives which have a POT on them which seems to smooth out these vibrations.


Is anything like this available for the KStep? If so, I would appreciate any guidance on how this is set up.


Thanks,


Scott
Group: DynoMotion Message: 11868 From: Tom Kerekes Date: 7/7/2015
Subject: Re: Stepper Motor Resonance
Hi Scott,

KStep doesn't have any tuning Pots.  What are your motor specifications?  What are your current setting jumpers configured to?

Regards
TK

Group: DynoMotion Message: 11869 From: lmp582002 Date: 7/7/2015
Subject: Re: Stepper Motor Resonance
Tom,

Here are the motor specs:


I have the current jumpers set at 3 amps. They are rated for 2.8, so perhaps I am a bit high, also running a 48V power supply.

Thanks,

Scott
Group: DynoMotion Message: 11870 From: Tom Kerekes Date: 7/7/2015
Subject: Re: Stepper Motor Resonance
Hi Scott,

That seems reasonable.  But you might try changing from the 3.13A to 2.5A setting.  Over driving the motor might cause distortion.

The motors are fairly low speed motors.  What speed gives problems?

What is the motor connected to?  How is it connected?

It seems to have an encoder.  You might connect it so you can plot exactly what is going on.  You might be able to add some active damping with feedback.

Regards
TK


Group: DynoMotion Message: 11877 From: lmp582002 Date: 7/8/2015
Subject: Re: Stepper Motor Resonance
Tom,

It is connected to a ball screw driving a small axis. I am using the encoder in closed loop to correct errors and make sure I fault if I loose steps. 

I have noticed problematic feed rates while running a CNC program. Is there a way to monitor the encoder output at various speeds to see what it is doing? I would be quite interested in active dampening if there is a good way to determine what the frequency is.

Thanks,

Scott
Group: DynoMotion Message: 11878 From: Tom Kerekes Date: 7/9/2015
Subject: Re: Stepper Motor Resonance
Hi Scott,

How is the motor connected to the ball screw?  Helical Spring coupling?  What do you mean by "Small Axis".

Does the vibration go away with the ball screw disconnected?

You can move at various speeds and plot encoder position using the Step Response Screen.  Change V to move at different speeds.  Set the "size" of the move to be long enough to have a sustained motion at the speed of interest.  Sometimes very low/gradual acceleration can be used to sweep slowly through a range of speeds.

See Video:

Regards
TK