I am trying to think out the box here so that I can move away from using steel for the frame. Having read a fair bit, I have concluded that steel is far from ideal for cnc rails due to the following.

1. Resonance
2. Thermal stability

As a result I have looked at casting the rails using epoxy granite and reinforced plastic beams. Both of which will have excellent damping. I am waiting on the tech literature for the recycled plastic beams as I am not sure what the thermal stability of them is.

http://www.lankhorst.co.uk/hst/l18a1...K?open&lang=UK

Interested to hear your thoughts on this.

Thanks