Vibration Damping

[Geof]

There have been a few threads on how to control vibration in machines and I have posted some thoughts on the topic.

I was reading a recent issue of New Scientist and came across the subject of "tuned mass dampers" or "dynamic vibration absorbers". For a light weight machine that has vibration problems these may be much more suitable than simply adding lots of weight to control vibration. These do add weight but it is a small amount in the correct place.

The first link is interesting. I think you could extend this to experiments on a vibrating machine that would just use a C-clamp and a weight on the end of a bar. Clamp it on in different locations with different lengths sticking out and then hit the machine with a hammer and see how it rings.

http://www.tinyurl.com/3cvzkt

http://www.newscientist.com/backpage...mg19626273.000

http://www2.eng.cam.ac.uk/~hemh/tmd.htm

[brunog]

Interesting topic, however the applicability isn't obvious,compared to other known methods, wheere the added weight is often placed in the machine's cavities.

Best regards

Bruno

[vger]

Geof,
Dynamic absorbers work well... if the frequency of the vibration is constant. They must be tuned so that the absorber vibrates and causes a counteracting force that reduces the vibration of the machine. I had an issue where an 800 HP motor was on a steel structure about 12ft tall that just happened to be naturally resonant very near the operating speed of the motor. A 6 foot piece of 1" by 4" steel attached vertically to the top of the support structure with a 20 lb weight about 8" from the top made the structure vibration almost stop. The weight was in motion about 2 inches, but less than .003" at the motor.

Steve

[Bobbyr70]

I have used a number of them and all but 2 worked great.
2 of them were applied in places where the vibration was not at a constant and the result was still very positive but the 1x4 steel broke after we tuned it to suit the best we could. A other areas have proven very effective. Never tried them in an application like a router table. Let me know how it works.