Bob, in the Tormach the spindle contactor (C2) is downstream of the main contactor (C1) that estop drops out. To duplicate your scenario the belt guard switch would just drop out C1--and lose the workpiece anyway.
As I pointed out, machine motion wouldn't all stop due to the backdriving head issue. Recent machines have a failsafe brake on the z-axis stepper to prevent this, but many machines in the field don't.
For something as trivial as the head door drifting open, something as drastic as an estop is hardly warranted. IMHO. One little bit of integration between the spindle subsystem and the axis drive subsystem would alleviate this problem entirely and possibly save workpieces without people jumpering the safety switch and defeating the safety interlock (I haven't, but know of people who have...)
Randy |