Re: [CAD_CAM_EDM_DRO] Active damping

> Les,
>
> Exactly what brand or kind of concrete would that be? Where would one

find

> some? I have some 3" square 1/4" wall tubing that is resonating as part of

a

> column on a small mill. I'd like to try the polymer concrete.
>
> Peter
> THRD, Inc.

Try this:
http://www.phillyresins.com/v2.htm

Note that several steel square tubes are placed inside a larger
steel tube and the space in between is filled with a damping polymer
compound. That material is therefore almost ideally
situated as a constrained layer damper. If you just filled the whole thing
mass would go up but not damping.

It would work with round tubes too.

I worked at corp r&d for the parent company so I know these people. But I
only learned about this a year and a half ago.
I had them send me some and it worked great. Wish I had known about it years
ago. It is patented but they encourage
the technique liscense free because they can sell more of their goop if
people use it that way. Or at least last time I checked.
Some vibration analysis I did showed that it does a great job
on steel weldments which tend to ring like a bell unlike good
old cast iron. As I said I will use it on future machines. I have to
actually pay for it now though!

If your machine is a mill drill I would characterize it as a mass
loaded cantelever. You need not just damping but stiffness as
well. Going to 1/2" wall tubing plus the damping would help
even more. A piece of 3"x.5" wall DOM welded tube would not cost much. Might
need collars as you would loose a little bit on diameter machining a nice
outer surface. Or use larger tubing.
Even solid would be good. Hey steel is a dollar a pound.

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.rabun.net/~leswatts/wattsfurniturewp.html