Exit conveyor off a stretch wrapper. Light curtain across the exit with two muting sensors, one each side, so a pallet going out mutes the curtain and a person walking in does not. Muting logic runs in a GuardLogix 1769 L30ERMS.
Since last week about every second pallet trips the curtain halfway through. Conveyor stops, pallet in the beam, operator walks round and resets. The muting lamp flickers off and on as the pallet goes through instead of staying lit.
So I checked the sensors are clean and aligned, and both indicate when I wave a hand at them. The maintenance lead reckons we turn the muting time limit up to max and be done with it, and I'm not sure that's an answer.
Only thing that's changed is the product, a new customer with shorter pallets. Curtain fault, or something in the logic? Any thoughts would help.
Shorter pallets is the change, start there. How far apart are the two muting sensors, and how long is the new pallet load. And is the load solid down the side, or is there a gap in the stack the sensor can see through?
Also, what is the muting timeout set to in the instruction, and don't touch it yet. Max timeout means the curtain stays muted with nothing in front of it. That's a person walking in.
Sensors are about 36in apart, one either side of the curtain. New pallet load is about 40in long, two cases stacked with a gap between them at the bottom, maybe 2in. Old product was 1800mm and solid. Timeout's at 10 seconds. Haven't touched it.
There's your flicker. The mute holds while both sensors are made in the right order. With 36in between sensors and a 40in load with a gap in it, the gap clears one sensor before the back of the load has covered the other, so the mute drops while the pallet is still in the beam. Solid 1800mm loads never uncovered a sensor, so it worked.
The curtain manual has a table for sensor spacing against the shortest load and the conveyor speed. Re-space the sensors for the 40in pallet, closer together, and check the timeout still covers the slowest pallet after the move. That's a sign-off with your safety person, not a maintenance tweak.
Moved the sensors in to about 24in as a trial, old holes marked, area roped off and nobody on the line. Ran ten short pallets through, lamp stayed on, no trips. Then one of the old 1800mm loads, same thing, lamp lit the whole way. Not running product on it until the safety guy has been.