The Packaging Line That Jammed: Mismatched Boxes, Not a Conveyor Fault
A packaging line folding and sealing cardboard boxes. It jammed every 20 minutes. The boxes came from a supplier. Some were the wrong size. The customer thought the folder-gluer was misaligned. The boxes were 5 mm too small for the machine’s setting. This is about box tolerances, not about the machine being defective.
The box tolerance problem
A folder-gluer is set for a specific box size (length × width × depth, ±1 mm). If the boxes vary by more than 2 mm, the machine can’t handle them. The supplier’s boxes were 400 × 300 × 300 mm nominal, but actual size was 395 × 295 × 300 mm (5 mm under). The machine was set for 400 × 300. The box was too small. It didn’t feed correctly. It jammed.
What we did
1. Measured the actual boxes. We took 10 boxes from the batch and measured. They were consistently 5 mm under nominal. The supplier’s die-cut was off. We told the supplier. They corrected the die. The next batch was within ±1 mm.
2. Adjusted the machine. While waiting for the corrected boxes, we adjusted the folder-gluer for the actual size (395 × 295). The machine handled the undersized boxes without jamming. The feed guides were narrowed by 5 mm. The fold rollers were repositioned. The line ran through the batch.
3. Added a box presence sensor. A photoelectric sensor at the feed detects if a box is present and at the right height. If no box (or a wrong-size box), the machine stops before jamming. The sensor prevents the jam by stopping the line at the feed.
The supplier communication
The box supplier needs to know the machine’s tolerance. We gave them the spec: boxes must be within ±1 mm of nominal. They added a QC check at their end. The boxes now arrive within tolerance. The jamming stopped.
The machine setting
A folder-gluer is a precision machine. It’s set for a specific box. If the box size changes, the machine must be re-set. The customer changed the box size without telling us. We re-set the machine for the new size. The jamming was a mismatch between the box and the machine, not a machine fault.
The packaging line rule: If a folder-gluer jams, measure the actual boxes. Die-cut boxes vary. The machine is set for a specific size. If the boxes are off by more than 2 mm, either correct the boxes or re-set the machine. A jam every 20 minutes isn’t a machine fault — it’s a box mismatch.
