Vibration Damper

[tachus42]

Seeing something like this http://www.directindustry.com/comm/l...mper_6214.html
on anothers manufacturers web site I thought that it must be possible to home brew one. Searching around the house for something with the required viscoelastic properties i found two foam discs fron a cdr spindle. They compress and are springy but bounce back slowly. Stuck both of them together and to a 1 1/2 dia 1/4 inch steel disc. Glued the other side of the foam to a plastic gear which was a press fit onto the rear motor shaft.

I wasn't really expecting too much ( or anything really ) but it works! Mid band resonance is signifigantly suppressed and I can get a 30% faster rapid.

It could possibly just be a enhanced fly wheel effect but i don't think so. The inertia of the disc wouldn't be a large fraction of the rotors inertia.

For a first quick hack this shows promise. The best foam to use would be one designed for vibration absorbtion like sorbothane. I found that McMaster Carr stocks small 4 inch squares for about 5 dollars. You can bet the commercial product costs a bit more than that.

[sendkeys]

nice anyone ever try them on servo's ? would it help maybe heat,percision or brush/bearing life?

[ESjaavik]

Servos don't need them. In fact they would perform worse. The dampers are there to help a problem that servos don't have. If your servo does not behave smoothly, it is not properly tuned.

[foamcutter]

Hi,
Have you thought of using a small round cup with a shaft collar ( to attach to motor shaft)for one side of the coupler and then a flat plate with a shaft collar (to attach to lead screw) for the other side and the flat plate would also need two small pins that woud protrude into the cup but not touch the cup. Fill the cup with silicon sealer, push the flat plate with pins into the silicon and let dry? I hope that makes sense to you, if not tell me and I will try to explain better. Ron

[sendkeys]

thanks ESjaavik

[tachus42]

foamcutter Putting the vibration damper in series with the load will help to absorb resonanace but will increase the position error.
The idea is to have the motor waste it's resonant enery trying to vibrate a small flywheel which is not coupled to the load.
Silcon sealer was one thing i considered a s the active element. There is a a metric called loss factor or delta tan which basically amounts to how much energy is lost when a material springs back after being compressed. Obviously for this application higher is better but i have no idea how much is enough. The only data i could find showed silicon rubber having a loss factor of between 0.07 and 0.15 . Differnet grades of sorbothane range between 0.3 - 0.6 . The bit of foam I used was proably nowhere near that.
It would be good if we could keep the disscusion going on this one and encourage a bit of experimentation.

[Tim Tanner]

Hi,

I have made simple vibration dampers for small size 42 stepper motors.

An annular steel ring is connected to the 5mm shaft of the motor by a small piece of neoprene rubber tubing 5mm ID, 9mm OD, push fitted into the hole of the steel ring.

The whole assembly is a push fit onto the motors 5mm shaft.

Neoprene is not the ideal material, not lossy enough, but it does help cure stalling due to mid-range instability.

I'd welcome suggestions of alternative materials in tube form to try.

Regards,

Tim.