Machsupport Forum
General CNC Chat => Show"N"Tell ( Your Machines) => Topic started by: chrisjh on August 25, 2011, 12:20:13 AM
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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
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Big difference indeed :)
Hood
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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...
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Good Job Chris! :)
Brett
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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
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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