Circulation Pallet Design: Locating Pins, Orientation and Lift Stations

The Pallet That Wouldn’t Locate on the Return Conveyor: Palet Stop and Docking, Not the Conveyor

A pallet on a return conveyor. It arrived at the workstation but didn’t locate — it stopped 20 mm short. The operator had to push it manually. The customer thought the conveyor was misaligned. The conveyor was fine. The pallet stop was adjusted wrong. This is about pallet locating on powered conveyors, not about the conveyor being defective.

How pallets locate

A powered conveyor moves pallets to a workstation. At the workstation, a stop (a pneumatic or mechanical blocker) rises. The pallet hits the stop. The conveyor motor keeps running (the pallet skids on the belt). A set of locating pins (cone-shaped) rises into the pallet’s holes. The pins center the pallet. The station is now ready to work.

What went wrong

The stop was set 20 mm too far forward. The pallet hit the stop 20 mm before the pins. The pins missed the pallet’s holes. The operator had to push the pallet 20 mm to engage. The stop position needs to be set so the pallet stops exactly over the pins.

What we did

1. Adjusted the stop position. We moved the stop back 20 mm. The pallet now hits the stop exactly when the holes are over the pins. The pins rise and engage. The pallet locates automatically.

2. Added a proximity sensor. A sensor detects when the pallet is against the stop. The PLC waits for the sensor before raising the pins. If the pallet isn’t against the stop (e.g., jammed), the PLC doesn’t raise the pins. No missed locating.

3. Used a flush-mount stop. The original stop was a pneumatic cylinder with a hard rubber pad. We switched to a spring-loaded stop (damped). The pallet hits the stop softly. It doesn’t bounce back 10 mm. It seats firmly.

The conveyor speed

If the conveyor moves too fast, the pallet slams into the stop and bounces. We slowed the conveyor to 100 mm/s (from 300 mm/s). The pallet glides into the stop. It doesn’t bounce. The pins engage on the first try.

The pallet locating rule: If a pallet doesn’t locate at the workstation, adjust the stop position. Slow the conveyor. Use a damped stop. Add a sensor to confirm the pallet is seated. The pallet that wouldn’t locate wasn’t on a misaligned conveyor — it was stopping 20 mm short of the pins.