Hi All,
I am somewhat new the CNC routers. Well, I recently built a nice little CNC router out of MDF, plywood and I used Arduino as the motion control with a dremel hooked up to it. It works very well, but is too small and slow to be useful for larger items. As such, I am making a larger CNC from steel and have a few questions about getting the rails and ball screws straight and square. Both the X and Y will be using 1500mm fully supported linear rails with ball screws driving both (20mm diameter on both). I have already bought the parts, so changing is not an option at this point (if I had to do over again, I might do R&P as ball screws could whip at higher speeds, but I cant change now).
Here are my questions:
The base that the gantry will ride on will be made of 4"x2" steel rectangular tube that is about 5' long. Welded together by by 3 rectangular tubes running perpendicular to both sides - basically a box that is make of rectangular tube. This frame will sit on a very sturdy table that I am making. The 1500mm fully supported linear rails will be on top of the rectangular tube with ball screw on the side of the tube. My question is, when I am drilling the holes for the fully supported linear rails to attach them to the rectangular tube do I make the holes slightly elongated so there is some play and once I get the rails perfectly straight then tighten them up? Or do I ensure the holes are absolutely perfect and have no adjustablity for the rail? If I make elongated holes, when I tighten the bolts, will that be enough to ensure they don't move?
The machine will be all steel and running NEMA 34's (I know 23's would have been better, but I have 34's) and will be used 75% for woodworking and 25% for aluminum. None of this was an issue with my MDF as there was some natural play and that was more of a prototype anyway.
Any help would be greatly appreciated. Thanks so much.
Rick