It's one of these: isel PPM 3-Axis 0322 ? When you say it's "stopping" - what do you mean by that? Does it just quit working altogether, or is the spindle bogging down, or is it kicking out an error of some sort? An intermittent electrical connection can cause a machine to stop unexpectedly - have you gone through all the wiring? If it only has that 100-watt spindle, I could see it bogging down even in wax, if you are trying to take a heavy cut. That might cause it to fault out, depending on the software that's running it = what does it use, a proprietary system of some sort? If you're using an unlicensed version of Mach3, that will stop after 500 lines, which can happen pretty quickly in a 3D program. The frame is probably strong enough to support some metal milling with small cutters run at high speed, but I doubt that spindle would be good for anything more than light engraving. What are you using to write the G-code that's stopping? It might also be a software problem that's terminating your program prematurely.