Forgot to hook up the air, went to “sleep” the machine… it docked the tool and ripped the mount right off.
At least it broke where I wanted it to; I’ve already printed a replacement and installed it.
And yes, I have a sensor that tells me when the air is off. It was on my desk at the time 
“Fail quickly, fail gracefully” concepts are the best low-tech way to keep your machine safe.
You are never close enough to that e-stop when the bad stuff happens.
I left the air valve half open one time so it had the pressure to disengage the draw bar long enough to release the tool. But when it came back down on the next tool the draw bar had already engaged as the pressure dropped.
Drove the tool down like a nail 
Two pressure sensors, one for system and one for the draw bar. Check before lift, check before seat as well. 
Somebody once told me on this forum that you don’t have to do any error checking on these CNC machines. I think he thought I was talking about errors in code 
Glad it worked out for you. Plastic is cheap.
