My plasma table design is coming along nicely. I am rebuilding my downdraft, water table and modifying it for cnc. I've got the motors, drivers (G540 gecko) , linear rails, cabling, and some of the miscellaneous parts. I am using belt drive on the Y and X axis and screw on the Z.
The G540 is a 10 microstep drive which gives 2000 steps per revolution. With a 10 tooth pulley and direct drive, this comes out to .0019" per step. This seems more than adequate for plasma machine. The motors have plenty of power for a direct drive and it's a lot simpler to build.
Does anybody have experience with direct drive machines and what accuracy is necessary ?
For plasma cutting the most important cosiderations are acceleration....which should be better than 40 miligees, smooth fluidic motion, and torch to work distance of plus or minus .010" max.
With your resolution you will likely see a bit rougher edge than you would expect with a servo drive....the plasma is burning at a constant rate so steps will show in the edge, but generally won't have an effect on accuracy. Plasma likes to cut within a rather narrow speed window...between low speed dross and high speed dross....called the DFZ (dross free zone).