I’ve noticed several table designs that start with a MDF or plywood torsion box as the platform upon which the CNC rests, supported by legs/framing constructed from lumber. The torsion box surface makes sense to me - coplaner surface for the four points of contact the CNC makes, no twist or warp, stable regardless of temp and humidity, etc. But those desirable features are not shared by legs and framing made from lumber. Doesn’t fastening a torsion box top to a support system that DOES move with temp and humidity cause problems? Why not an entire structure made from MDF?
John,
I’ve been using Torsion Box bases for CNC for 5 years now (several machines) and I live in TX, so we defiantly have massive humidity swings here. I have never had an issue personally. My assembly table is also a very large Torsion Box with zero issues.
Not sure what others experiences have been but for me its still the best option for a rock solid platform.
-Alex
Thanks Alex - I too have a large torsion box assembly table - (4ft x 5 ft) 3/4 MDF skins with 1/4 MDF webbing - sitting atop integral cabinets also composed of 3/4 MDF (no lumber anywhere) and found that to be extremely stable but also very heavy. A base of 2x lumber supporting a torsion box would be much lighter and easier to move around but I wasn’t sure if that could introduce problems down the road.
All my torsion boxes utilize MDF tops, with 3/4 plywood as the rest of the TB. On my Onefinity, I have 2 layers of MDF for the top but doing this keeps it lighter and I have not experienced any loss of integrity with this approach. I use dimensional lumber for all my supporting structures that the TB sits on.
I agree doing the entire thing out of MDF is a trip to the Chiropractor waiting to happen. 
-Alex
Mdf is what I used and I think ply inside may provide better rigidity.