Question to anyone: What are you using for a safety interlock to prevent the power drawbar from releasing if the spindle is turning?

Speaking for myself, I do not trust MACH with such an important job, so I would be looking for something autonomous, or activated by the servo drive and not by MACH. I am thinking about a spring loaded solenoid that must retract a mechanical interference from the mechanism before the drawbar can release. Perhaps steal some energy from the motor to drive a relay to keep the 'lock' in place until the motor has zero energy. 

The drive I am using can sequence everything with an internal program, but I am looking also for a more 'generic' and autonomous solution which would work with less sophisticated drives.

The only reasonable thing I've been able to come up with is making the ram button on the end of the air cylinder rotate. Then have a wire that the 24VDC that runs my estop system run through it like it was another estop switch. If the ram comes down while the spindle is turning then the button will turn break the wire or contact and kill the 24V. My estop system is totally separate from Mach. when you kill the 24V you kill everything. Servos, VFD,coolant and the air valve for the draw bar. The air valve is a spring return so when you kill the power the default is up.
Not elegant but for an electronics ditch digger like me it will get it done. I've been working with Mach daily since it was master5 and never witnessed it activate an output on its own.
Having said that it wouldn't surprise me at all if it happened tomorrow. That's why my estop has nothing to do with mach.

Speaking of drives what are you running? I'm looking at the Delta VFD-M series. it's in the right price range , takes single phase input and has simple indexing to align the drive lugs.

the relay that enables the vfd/spindle drive can be used to isolate the solenoid operating the drawbar.

the relay that enables the vfd/spindle drive can be used to isolate the solenoid operating the drawbar.

In this case, I think the drive would need to be disabled in order for the drawbar to work. With the drive disabled there would be no mechanism (other then a spindle lock) to make sure the spindle is stationary.

ah i see it's the need for the spindle to be stationery for the drawbar to operate you'tre worried about. Add a tacho to the spindle and use this to operate a relay that disables the drawbar.

The only reasonable thing I've been able to come up with is making the ram button on the end of the air cylinder rotate. Then have a wire that the 24VDC that runs my estop system run through it like it was another estop switch. If the ram comes down while the spindle is turning then the button will turn break the wire or contact and kill the 24V. My estop system is totally separate from Mach. when you kill the 24V you kill everything. Servos, VFD,coolant and the air valve for the draw bar. The air valve is a spring return so when you kill the power the default is up.
Not elegant but for an electronics ditch digger like me it will get it done. I've been working with Mach daily since it was master5 and never witnessed it activate an output on its own.
Having said that it wouldn't surprise me at all if it happened tomorrow. That's why my estop has nothing to do with mach.

I am running 62 dev version because that is what works with the PoKeys board that I am messing with. You cannot use the 'stable' version with PoKeys and 62 has broken B and C axis feedrates and also has a tendency to either have fatal errors or just up and quit without warning.  I have a screen macro that simply lights an LED and activates an output. The LED always lights, but the output would go high sometimes and sometimes not.  When Mach starts and exits (intentionally or otherwise) andwhen the PC starts up or shuts down, or when Smoothstepper has a tantrum, it is hard to predict what any pin is going to do.  My safety interlock will be a mechanical device which will provide a positive physical impairment of the drawbar movement. I just have not decided how to arrange it.

Speaking of drives what are you running? I'm looking at the Delta VFD-M series. it's in the right price range , takes single phase input and has simple indexing to align the drive lugs.

My spindle motor is using a Copley Controls Xenus drive. 165V 40A on single phase 120V. Will also run on single phase 220V, but the bus voltage also doubles. The motor is 140V 37A peak.

ah i see it's the need for the spindle to be stationery for the drawbar to operate you'tre worried about. Add a tacho to the spindle and use this to operate a relay that disables the drawbar.

There is a spindle lock that the motor cannot overpower, and the motor actually has a tacometer built into it. It puts out 7V per thousand RPM if I remember right. That is an interesting option, thanks!

For BT30 or any other scheme that has drive dogs, the spindle must home and stay homed. Not all spindles have locks and I am looking for the most universal solution . .  i.e one that the typical mill could use . .  although really I don;t know what 'typical' means 

There is that functional issue, certainly, but what I am focused on is preventing the adapter from being ejected unexpectedly at 7,000 RPM with a sharp tool in it. I am beginning to get the impression now that a safety interlock is a foreign topic.

Well I was planning on using pokeys to run the ATC so it looks like I'll be in the same boat as you! On this machine I'm not running the smooth stepper so that should remove one area of uncertainty. I'm running a smooth stepper on my router and have experienced some quirky actions for sure.

There is that functional issue, certainly, but what I am focused on is preventing the adapter from being ejected unexpectedly at 7,000 RPM with a sharp tool in it. I am beginning to get the impression now that a safety interlock is a foreign topic.
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then my earlier reply will sort that.

"the relay that enables the vfd/spindle drive can be used to isolate the solenoid operating the drawbar."

ah i see it's the need for the spindle to be stationery for the drawbar to operate you'tre worried about. Add a tacho to the spindle and use this to operate a relay that disables the drawbar.

Ultimately you would want this as a separate entity from Mach. Then at some point you have to decide what do you trust more. Mach or the circuitry your using to monitor the tach and activate the relay.
Not slamming your idea just trying to draw it to the next conclusion. Ultimately I like this idea if it was safe.