This is my first CNC project and my second post on this forum. I am wondering what materials I can build the frame out of given that I have basic woodworking tools such as table saw, router and scroll saw. Unfortunately I do not have any serious metal working tools. I have an electrical background so I didn't have much trouble with selecting the motors, driver board and power supply. I ended up going with the Rockcliff 4 axis kit http://www.rockcliffmachine.com/electronics.htm . I have already got the 4 axis kit up and running on the bench without issues.

Anyway my question is what material I should use to construct the machine. I assume that MDF and plywood are two of the options but I am not sure if there are any plastics that might be more robust and more dimensionally stable. If there are not any plastics that would work well for this and I am stuck using wood is there anything that the would should be coated with? The machine I am planning on building the is the model D from the rockclliff cnc plans which is a flying gantry machine with two motors driving the Y axis. I am considering scaling the design up slightly so that it can accommodate a 4'x4' sheet of MDF or plywood.

Any advice on material selection would be greatly appreciated.