Damping Machine Frame

Hi guys,

I've had my machine working for a while now and while it seems pretty stiff, I think I could do with damping it better. Apart from a layer of 10mm HDPE affixed to the top of the bed with a special damping glue, it is not damped at all.

I know how it should be ideally damped, having read the paper posted here a little while ago - http://www.mycncuk.com/forums/faqs-p...mn-design.html

This would be layer damping with a viscus layer held captive between two box sections, one within the other kind of like layers of an onion. However, this requires a fair amount of extra metal to go down the centre of each part of the frame, and basically taking the whole machine to pieces to do the job. I don't have the money nor time for that at the moment. I was wondering how effective people have found more simple methods such as filling any box-section with expanding foam or sand?

I imagine this might damp the frame at audible frequencies when you tap it, but at low frequencies such as standing waves along the length of the frame, it might not make much difference at all. What do you all think, is it helpful to do the quick job or is it pointless and I need to do it the long way?