Side-Seam Forming in Paper Bag Machines: Controlling Glue and Fold for Leak-Free Bags

The side seam is where a paper bag's strength and seal are decided. Side-seam forming folds and bonds the paper into a tube, and the glue line must be continuous and correctly positioned to hold contents without leaking. Controlling the fold alignment and glue application produces strong, leak-free bags at speed.

The Scenario: The seam decides the bag

Side-seam forming faces three challenges:

Pain Points

• A weak or broken glue line causes the bag to split or leak under load;
• Misaligned folds produce crooked seams and off-spec bags;
• The seam must hold at high machine speed without defects.

The Solution: Three side-seam solutions

Three practices build a strong seam:

1. Continuous glue line A continuous, correctly positioned glue line bonds the seam for leak resistance.

2. Aligned fold control Accurate folding keeps the seam straight and the bag on spec.

3. Speed-stable forming The forming process is tuned to hold the seam at high production speed.

The Result: Strong, leak-free bags

With controlled side-seam forming, bags are strong and leak-free at speed. This reduces returns and builds customer trust.