I am running 740 oz in steppers on a table designed as 5' X 10' cutting capacity the gantry is all steel & overall length is around 6'. An educated guess on the weight including all motors, drive reduction assemblys, wire, hoses, solenoid valves, Ox/Fuel torch head, etc. to weigh in excess of 100#
I have (2) steppers on the long axis in a master/slave configuration. It is easily achieving 200 IPM or if I am converting correctly apx. 5000 MM per min.
The only time I have lost position was accidentally hitting an "E" stop button while under rapid move. Even then It didn't cause a problem as I simply came home & re-referenced the X & Y to 0.00
For the THC If you regurlarly cut thin material, especially thin stainless Go with the THC1000 from CandCNC.com Campbell's THC is a good unit but will struggle keeping up with rapidly warping materials & continually search for & overshoot the targeted height.
A 2" ballscrew is huge, heavy, & way overkill for the project at hand. Again I'd use rack & pinion
Something else I should ask or get clarified. I have been assuming your machine is a gantry design & not cantilever. If it is cantilever it will be nearly impossible to cut at high speeds with plasma. You just will not be able to control the flexing under rapid movement changes.
I want to make it clear I have no affiliation with
www.CandCNC.com . I would seriously take a look at using their Power supply & controls. Price alone doesn't tell all the story. Tom has went to great lengths to build a product with a tremendous amount of self preservation built into it. Not to mention everything is pretty much Plug-N-Play.
It's one thing to save some $ & spend loads more time wiring, testing, then troubleshooting. if your table is home shop or hobby. I'm of the opinion if you need the conversion of the table in a timely manner & need to depend on it daily. Your companys money would be well spent to get that part of the conversion in a package deal. Whether it be stepper or servo everything is designed to work together & self protect each respective component right back to the PC.
I am not nearly as experienced with CNC control as many of the others on this board. My comments are from my own personal experience & merely my opinion. Here is a link to my build log for my table.
http://www.cnczone.com/forums/showthread.php?t=31133 Somewhere toward the end are a few short video clips of the table cutting & moving under rapid moves. That should give you some idea of the speed you can achieve with a stepper system. Keep in mind my steppers are 740 oz. in. & much more powerful steppers are avalible.
Neil