Quote Originally Posted by Jonathan View Post
I would have thought polyester resin would be fine since it's only filling the frame.
Polyester isn't suitable because it shrinks too much apparently, I would refer you to the exact part of the epic thread on cnczone where that is discussed but I'm not reading that bloody thing again!

Quote Originally Posted by JoeHarris View Post
Is it really necessary to start filling your frame with resin?!
The whole point of being a cheapskate diy chappie is spending the least amount of money possible for the quality you want, if your machine is serving you great with steel box then it ain't broke so don't try and fix it. If you want better stiffness and vibration dampening to give better quality then it's an option open to you.