Machsupport Forum

General CNC Chat => Show"N"Tell ( Your Machines) => Topic started by: chrisjh on August 25, 2011, 12:20:13 AM

Title: How I solved my Stepper Motor Resonance Problem - Video
Post by: chrisjh on August 25, 2011, 12:20:13 AM

I have had a terrible problem with bad resonance with the Z Axis on my CNC Lathe.  The problem only appeared at certain feed rates.  The lathe has smooth operation at most feed rates.

In desperation, I had to try to program around the feed rate that I wanted to use (0.25mm/rev) to avoid the resonance; as it was affecting the quality of turned parts. I.e. I would use a non-ideal 0.15 or 0.35mm/rev to avoid the problem.

I tried all the advice that I could find on the internet to no avail. I even changed the Stepper Motor and Stepper Motor Drivers to a different makes.  No luck.  I tried varying the Power Supply Voltage to the Driver with absolutely no effect.

I then tried a mechanical approach by adding a flywheel to the Z Axis Stepper Motor.  Bingo!!!  Why didn't I do this 3 years ago?  So simple and so effective!!!

The video shows a wobble in the flywheel which resulted from my poor hand tapping skills.  I will make a new flywheel when time permits; now that I seem to have the problem licked.

The flywheel is Ø99 x 14 thick and made from mild steel.  There was absolutely no maths used; rather a simple application of the laws of physics and gut feel!!!

See video here  http://www.youtube.com/watch?v=mqCL7g4gwAU (http://www.youtube.com/watch?v=mqCL7g4gwAU)

Regards

Chrisjh

Title: Re: How I solved my Stepper Motor Resonance Problem - Video
Post by: Hood on August 25, 2011, 11:40:25 AM

Big difference indeed :)
Hood

Title: Re: How I solved my Stepper Motor Resonance Problem - Video
Post by: Haik on June 13, 2013, 04:01:56 AM

Inertial Dampers and flywheels are very effective for helping nullify resonance within a rotational mass. Here is my NEMA 42 stepper with a multi-part damper at work...

Title: Re: How I solved my Stepper Motor Resonance Problem - Video
Post by: Chaoticone on June 13, 2013, 07:03:16 AM

Good Job Chris!   :)

Brett

Title: Re: How I solved my Stepper Motor Resonance Problem - Video
Post by: DICKEYBIRD on June 13, 2013, 05:15:27 PM

Here's an old thread showing how to make a "rattler" style stepper damper.  It's very effective.
http://www.cnczone.com/forums/stepper_motors_drives/32284-take_stepper_damper.html

Title: Re: How I solved my Stepper Motor Resonance Problem - Video
Post by: chrisjh on June 15, 2013, 07:11:21 AM

Hi,

I have been using this flywheel mechanical damping system successfully for a couple of years now.  It is interesting to place your hand lightly on the revolving flywheel when feeding at 0.25mm/rev, to feel a very distinct "pulsing".  It actually feels quite violent.  But the end results (finish) speak for themselves.

Obviously (hindsight is a wonderful thing), my resonance was purely mechanical and, probably the result of length and elasticity of ballscrew shaft combined with other moving masses at one particular frequency.

Regards

Chrisjh