Quote Originally Posted by HankMcSpank View Post
I guess ultimately then, it's how much do you trust the relay (or more so, the relay contacts) that controls the spindle startup! (I'd figured there'd be a little more 'conditional' scenarios involved before a spindle could be allowed to start)
Not really the relay contacts because it's a NO relay and when signal drops power to relay coils the contacts break naturally ( Unless faulty in which case it won't stop anyway.!)
It's the control software or more accurate the signal state you can't trust and in extreme case's it's possible it could switch state thru noise interference.!!

You could build into the Macro some conditional checking like checking the state of a input. This could be done by using double throw relay which sets a spare input used has a NOT-READY-NO-GO
This is one of the reasons for using a M6 tool change macro. It's in this macro where you'd put code for things like auto tool changers etc and also for doing safety checks like this if needed.! (could even turn kettle on for you for quick brew between changes. . Lol)