Ons of the originators of damped PU compound of course is Sorbothane - though whether they sell the resins to cast your own I don't know.

Quote Originally Posted by pippin88 View Post
For a 3D printer gantry I would think about carbon fibre instead. Stiff and damp.
Stiff yes, damped not always in my experience, I guess it all depends on the type of resin used to bind the fibres. A pal of mine who works in F1 gave me a sheet of thin (~0.5mm) woven carbon fibre sheet - if you hold it up and tap it with a hard object it sounds like tapping a sheet of metal - and the edges are bloody sharp!