My Machine is built from extruded aluminum box rails with aluminum plates for the gantry and steel tubing for the slide rails. Aluminum angle and roller bearings where used to create the slides. Although this system works perfectly, If I where to build another I would probably go with linear slides for the gantry just to add additional precision. I can cut 1/4" ply at about 20-25in/min, balsa can be cut as fast as I desire. I have cut aluminum with this machine but it is hard on the router.