Shrink-wrapping technical guide
A practical engineering guide to separating film, sealing, heat-tunnel, presentation, transfer and cooling causes before settings are changed.
Troubleshooting method
Shrink-pack defects can begin in product presentation, film selection, sealing, tunnel exposure, transfer or cooling. A disciplined sequence avoids using more heat to hide a film, seal or handling problem.
Compare the defect with the last accepted pack and recipe. Check whether the product, fill level, product temperature, reel supplier or code, film gauge, print, pack pattern, operator method or line rate changed. An apparently mechanical fault may be a material or product change.
Look at the unshrunk film envelope, seal, perforation, product orientation and transfers. A weak seal, excessive film, trapped air, sharp corner or unstable group will often remain visible before tunnel entry.
Record actual conveyor speed where it can be verified, product spacing, tunnel loading, indicated temperature, airflow or fan setting and cooling arrangement. Do not assume a displayed set point proves the physical condition is unchanged.
Operators should only perform adjustments and cleaning allowed by the supplied manual and site procedure. Stop and isolate the equipment for unusual noise, smoke, electrical concern, damaged guarding, uncontrolled heat or any condition that cannot be diagnosed safely.
Record product, film code, recipe, actual speed, loading, photographs and the point at which the defect appears.
Inspect product presentation, film path and seal before the tunnel, then observe the heated and cooling stages safely.
Make only an authorised, controlled adjustment so its effect can be understood and reversed.
Repeat the normal load, production gap and restart, then retain an accepted sample and final settings.
| Observed defect | Likely process areas to inspect first | Controlled checks |
|---|---|---|
| Loose film over one or more faces | Film shrink response, airflow access, conveyor speed, pack spacing, thermal load and product orientation | Confirm reel identity; inspect airflow obstruction and pack position; verify actual speed; compare the accepted recipe under normal loading |
| Large corner folds or “dog ears” | Loose-film envelope, product geometry, film shrink balance, air release and seal position | Check film amount around the product; compare corner geometry; inspect perforation/air escape; trial one controlled adjustment at a time |
| Holes, splits or burn-through | Sharp edges, damaged film, excessive local heat, weak seal edge, poor transfer or contamination | Inspect the unshrunk film and contact points; locate the hole relative to corners/seal; check airflow hot spots and actual belt speed |
| Open, weak or intermittent seal | Film identity, contamination, film path, tension, pressure, dwell, approved consumables and seal surface condition | Inspect the seal before the tunnel; clean and maintain only under the machine manual and safe isolation procedure; compare with an accepted seal sample |
| Pack twists or product group moves | Unstable collation, guide pressure, conveyor transfer, loose-film drag, airflow force and early shrink | Run the group without film where practical; check guides and transfers; confirm product spacing and support through tunnel entry |
| Wrinkled sleeve label or neck band | Pre-heat placement, container profile, sleeve dimensions, seam, print, local airflow and cooling | Measure sleeve position before heat and after cooling; confirm layflat/cut length and the exact container/closure |
| Product, label or surface marks | Heat sensitivity, warm-film pressure, sharp guides, insufficient cooling or product contact | Check product condition before and after heat; extend/verify cooling; inspect downstream contact and compression points |
| Quality declines during a long run | Thermal loading, heater recovery, fan condition, product temperature, spacing, belt speed or material change | Compare first-off and steady-state settings; record loading and product temperature; check whether any reel or product change coincided with the drift |
Fault evidence
A clear evidence pack helps internal engineers and Lancing distinguish material, setup, line and equipment causes without repeating uncontrolled experiments.
A hole that repeats on the same product corner suggests a different cause from random holes across the film. A wrinkle that begins before heat differs from one created during cooling. Mark the location and orientation consistently.
Retain a pack from initial setup and another after the tunnel reaches normal production loading. Differences can reveal thermal recovery, spacing, product-temperature or material effects.
A correction is not complete until it survives the normal run, a production gap and restart without forcing operators to chase settings. Update the recipe and accepted sample only after that proof.
Not automatically. First confirm the exact film, seal, air release, actual conveyor speed, airflow access, pack spacing and thermal loading. More heat can damage the product or film while leaving the original cause unresolved.
The tunnel may be responding to sustained thermal load, changing product temperature, tighter spacing, fan/heater condition or a material change. Compare first-off and steady-state evidence rather than relying on a single sample.
A tunnel cannot reliably repair an open or weak seal. Inspect film identity, contamination, seal surfaces, pressure, dwell, tension and approved consumables before the pack enters the heated zone.
Stop and follow the site isolation procedure for damaged guarding, unusual noise, smoke, electrical concern, uncontrolled heat, mechanical damage or any condition that cannot be checked safely within operator authority.
Show the product presentation, film and seal before heat, tunnel entry, discharge and the finished defect from a safe position. Include the reel label and machine display without exposing credentials or bypassing protection.
Application review
Include the machine identity, product, production film, last accepted recipe, loading condition, defect timing, photographs and any safely recorded run video. Lancing can then review the process stage most likely to require attention.