What if the spindle stops?

[WoodSnarfer]

If you have a servo motor moving your axis, and say you are cutting either metal or hard wood -- and for whatever reason the spindle (or router) stops -- what tells the servo controller to stop moving the axis?

I realize that servo drives have current limiters, so is that what you depend on? I'm thinking that if there is a tool failure, I don't want my servo drive to be trying to move the halted cutter through material. If something like this were to happen, there must be a lot of EMF that has to go somewhere.

So, what is the safety net that you should employ to keep the magic blue smoke from coming out of either your control box, or your servo? Good old fuse on the power supply enough to do the trick, or something more sophisticated?

Thanks,
Chris

[Al_The_Man]

That all depends on the nature of your control and what type of spindle control you have.
Often with spindles that have drives for control, there are outputs like at-speed or spindle fault which the control reads and immediately does a feed hold or e-stop, depending on the designer.
With no spindle controller you would have to rely on current limiting in the drives.
Al.