Quote Originally Posted by Jonathan View Post
Yes of course you'd include the spindle in the circuit I described ... though that was obvious!
No you didn't make it obvious and knowhere did you describe killing the spindle and thats the problem when dealing with electrics and control box's.? . . Those that know just take it for granted.!! . . Which doesn't help Folks new to CNC who just pickout bits but miss or don't understand the important bits. (Whether you think they are important or not is upto you.!!)

To have truely safe control box things need to be isolated with power killed to some items and signals broke or sent to others then a signal sent to the control software informing an E-stop as occured and then only allowed to be reset when all safety features IE: limits, E-stop etc are good and working.
An Estop when reset shouldn't allow the power or signals to be re-applied or reset the software. ( I suspect your killing enable signals would do just that without some latching mechanism built in.? Maybe you should clear this up with more INFO.?)
Yes VFD's need treating slightly different but most have provision for this with emergency stop functions built into them and can be safely shut down by killing the correct signal, infact good one's will even DC brake the spindle for you when it see's the E-stop.
Bottom line is.!!. . . The system should only re-apply signals or power when all is correct and safe to do so and then only by pushing a dedicated restart momentry switch. Which then and only then tells the Control software it's safe to allow a restart.

We could disagree all week on the best way to achive this I'm sure.!. . . But the point I'm making is that software driven is not safe and shouldn't be used if you want a safe system. What's even dafter IMO is why wouldn't you want to be safe and protect you and the machine when it cost's so little extra to do it right or safe.