Why Are Seals Uneven Across the Width?

Problem

Tear-testing sample packages shows one side of the seal releasing much earlier than the other, or a visible difference in seal texture across the width. The pattern repeats package to package at the same position.

Possible Causes

1. Jaw pressure is uneven across the seal face.
2. Jaw faces are worn or contaminated unevenly.
3. Wrinkled film enters the sealing area and locks into the seal on one side.
4. Temperature is not stabilized, or heats unevenly across the jaw.
5. Sealing jaw alignment has shifted after mechanical work.

What to Check

• STEP 1Compare the jaw impression.Close the jaws on a piece of paper per the machine manual and compare the impression left across the width.
• STEP 2Inspect the jaw faces.Look for uneven residue, scoring or polishing — one worn end produces one weak side.
• STEP 3Check the incoming film.Confirm the web is flat entering the sealing area; wrinkles on one side seal in as weak lines.
• STEP 4Verify stabilization.Confirm the sealing temperature has reached steady state before evaluating samples.
• STEP 5Review recent mechanical work.Check the maintenance record for jaw or sealing assembly work preceding the fault.

Corrective Actions

• Restore even jaw pressure per the machine manual and re-verify with the paper impression.
• Clean jaw faces; recondition or replace when scoring or uneven wear is found — request via the spare parts form with photos.
• Resolve upstream film wrinkling before re-evaluating seal quality.
• Re-qualify with consecutive sample packages after every correction.