I have designed a large moving table CNC router and would appreciate any observations about it's design and mechanical connections. The cutting volume is 1.5m x 3m x .95m. I intend to cut 3d shapes from low and medium density foam for theming which I will coat with epoxy or other hard skin.
I also posted the images of this design as part of another thread: http://www.cnczone.com/forums/showpo...3&postcount=10 but have added them here too if that's OK to get some design input.
Basically, the drive mechanism is R&P on all axes ala Mechmate with 7.2:1 geared Nema 34 steppers. Two steppers drive the moving table. The z axis is assisted against gravity by two cable retractors. The linear motion is comprised of Dual Vees riding on steel angle spot welded at 45deg on the support members. I've calculated the deflection on the gantry to be about .015 in approx based on 150lb y axis car and z axis assembly.
The moving table assembly will be bolted to the slab and leveled with the mounting bolts and aligned to the fixed gantry above. It seems like the most critical part of the construction is to align the angle iron tracks to the beams and to themselves. The gantry uprights as they exist don't seem to be a very elegant solution. The gantry gets it's rigidity form a friction bolted connection on each end.
I've not connected the gantry structure to the table because it results in a lot of extra steel and connections. I've noticed that a number of the large CNC machines rely on the slab connection. I'm only looking for a tolerance of about 1 or 2 mm. I expect to sand the finished product lightly before finishing it.
The areas I'm not so sure of in this design are the connections between the gantry and the uprights and the construction of the moving table. Any and all input is welcomed.
David