Hi Tom, Yes I have looked at the Al sections and i do have some of the item ones, It just seems an expensive route (espessially if you go for the heavy range) once you get all the connectors fixings ect. If budget allows then use it. It sure is much easier and dose look very proffessional.

Cheers for the link that looks good, not sure on the bearings tho, they look similar to pnematic actuators but could just be a low profile rail. with that design the forces will be small so could be similar to the igus stuff.

The small z axis definetley helps as it reduces the loadings. I think the main point here is that it is being used as a router for fairly low precision work. which is much easier than the breif of this project to cut Al.

I only thought of the u channel as it can be accuratley drilled by an MDF machine and then bolted/welded together to make a strong frame.

I was pricing up the large uprights in 15mm Al and realised how expensive they are to buy and get machined. I figured that they only need to be that thick because they are 2 dimensional, if there was some bracing in the 3rd dimension then they could be a lot thinner, hence the 3.175mm U channel. I maybe wrong and someone else has already tried and failled.

Is it worth Re-clarifiing the goal, As I understand its a 2"x4" (cutting area?) mid range with Al frame(that can be made on an MDF machine if required) and uses supported round rail or linear bearings with ballscrews to cut Al.????? Probably £500 for frame and rails (ballscrews vs lead screw and motors/drivers optional)