Programatic Light Curtain Muting

Scenario is robotic cell that stacks pallets onto conveyors. Conveyors move stacks of pallets out of cell to pickup location. Cell is fenced except across outfeed conveyor in question where a light curtain is used to guard.

System is using a Safety PLC and standard practice would be to use muting sensors wired to safety inputs to control muting of Light Curtain when pallets feed out.

Question I've been asked is if we can omit the sensors and use PLC non-safety rated output turned on when Conv running to mute Light Curtain?

My gut tells me know but we have multiple robotic cells built by other OEMs in our facilities who are using programmatic muting.

The reason it's being questioned is because space is tight and I'm having trouble finding sensing solutions for muting that will not be prone to seeing through the holes in pallets and can be places close together.

Any insight into the programmatic muting or people who've had good success with a particular sensing strategy for seeing pallets continuously as they convey by is much appreciated!

Pallet conveyor is a pain. Is there anyway to only look at the board running the length of pallet? (stringer board top two inches)

Hopefully your using chep pallets? If your using green pallets it can be a nightmare with automation. Broken boards running perpendicular to travel are an issue too.

MY recommendation is always look at the stringer board top two inches of the board that is traveling. look at pallet image.

If your using the attached pallet, i would see if you can used dried out pallets and not bring pallets that have been in the rain or outside to run in your system.

Anywhere we are detecting empty pallets, or have to rely on looking at the pallet itself, we use:

RK46C.DXL3/4P-M12
BRT-84X84A

We look at pallets a lot, that sensor has been the most reliable. What makes it nice is that the entire beam doesn't have to be blocked for it to change state, only partial block.

I always consider that if a non-safe PLC output is able to mute a safety device, the safety device may as well not be there.

I’m very lucky in that I’m looking at chep 4 way (no stringer) and standard (stringer) pallets of varying heights and qualities. The cell actually sorts the pallets so no consistency. I will look into the Lueze sensor though. That might be the ticket!

L D, I tend to think the same myself, hence my surprise to see other robotic integrators doing such a thing.

For real fun and games try looking at pallets on a CHEP sort line, this is where the pallets get inspected for type (stringer/block/someone elses) and then sent to the appropriate restacker cell. These pallets come in with missing/damaged boards stringers/blocks on a continous basis.
Prior to safety caging the entire line we had our best success with Banner Q45 ultrasonics.

Soggy that’s pretty much what this cell does. Takes in stacks of good/bad chep/non-chep pallets scans them, then stacks them into categories. So I feel all of your pain. I’ll check out the ultrasonics as well.