Hello everyone. Machine we shipped six months ago, a small polishing spindle in an enclosure. Compact GuardLogix 1769-L30ERMS, TLS3-GD2 solenoid lock on the door, spindle on a PF525 with STO off the safety outputs.
Customer rang this morning. Operator hits Stop, the lock lets go about a second later and the spindle's still turning. With a heavy polishing wheel it takes eight seconds or so to run down. Nobody got hurt, but somebody opened that door onto a spinning wheel.
I'll own the logic. Stop drops the STO, a timer in the safety task runs 1000 ms, then the lock output releases. I took the 1000 ms off the bench, where the ramp had it stopped inside a second with a small wheel, and I checked nothing else.
They're asking for a faster brake. Any thoughts on what that release should really be waiting on?
Trend it before anything else. Spindle speed from Stop to zero, heaviest wheel, no load, worn belt if it has one. And to be clear, right now the lock is waiting on a timer off the Stop command, not on anything that knows the spindle stopped?
Timer, off the Stop command. Nothing that knows the speed. On STO the drive coasts, so the ramp means nothing, I can see that now. I think the bench number was the ramp and never the coast.
What does the risk assessment say about access while the spindle is rotating? That decides whether a validated time delay is acceptable at all, or whether you need safe speed monitoring. Ask the customer's safety person for that page. One thing to do tomorrow: measure the coast with the heaviest wheel they actually run, not the one you shipped.