Film process guide
Intentional perforation can give trapped air a controlled escape path as film collapses. The required method depends on film, seal pattern, pack geometry and the accepted finish.
Direct answer
As shrink film heats, it contracts around the product while air inside the loose pack needs a route out. Approved perforation, open sleeve ends or another designed air-release path may provide that route. Too little release can cause ballooning and delayed film contact; an unsuitable hole pattern can affect appearance or protection. Use the production film specification and do not add or change perforation without approval.
A weak or incomplete seal can leak unpredictably and then fail as the film pulls. An oversized bag can trap more air and create large fins. Confirm film size, seal condition and product orientation before changing the tunnel.
Supplier perforation is part of the film specification. Random holes, splits or burn-through can come from sharp edges, damaged reels, sealing, contact with hot surfaces or excessive local exposure. Record where and when each hole appears.
Deep recesses, hollow shapes and broad flat faces can retain air differently. Perforation position, seal location and orientation should be assessed with the actual product, not a generic flat test piece.
Increasing temperature or slowing the conveyor may collapse film more aggressively but can overload the seal or damage the product. Diagnose air release, film, seal, airflow, speed and loading as one process.
Diagnosis sequence
| Observed condition | Check first | Then confirm |
|---|---|---|
| Large balloon before film collapse | Bag size, seal, approved perforation/open ends and product cavities | Airflow, actual speed, loading and product movement |
| Random holes before tunnel entry | Reel damage, sharp product features, film path and seal cut | Handling, contamination and film specification |
| Holes appear in one tunnel location | Product contact, local hot surface, airflow concentration and orientation | Film gauge, exposure and pack spacing |
| Loose film remains after cooling | Correct film code, film envelope, seal and air release | Shrink curve, actual speed, airflow, thermal load and cooling |
| Seal opens as film shrinks | Film compatibility, cleanliness, alignment, pressure and dwell | Bag size, trapped air and shrink force around the product |
Buyer questions
Small holes may be intentional perforation designed to release trapped air during shrinking. The hole pattern is part of the approved film and process specification. Random holes, splits or burnt areas are defects and should be investigated separately.
Do not introduce an unapproved perforation method. Hole size, density and position can change appearance, protection, seal loading and repeatability. Confirm the required air-release route with the film supplier and machine provider, then record it as part of the approved process.
Air is being heated inside a loose film envelope faster than it can escape or the film can contact the product. Check the seal, bag size, approved perforation or open ends, product cavities, airflow, actual conveyor speed and loading. Ballooning is not automatically solved by more heat.
Yes. An unsuitable hole pattern can be visible, reduce the intended surface protection or create inconsistent collapse around the product. The correct method depends on the pack and film specification. Use production samples and an agreed acceptance standard.
Intentional perforation should be repeatable in size, pattern and position according to the film specification. Damage is often irregular and may align with a reel edge, sharp product feature, film path, seal or tunnel contact point. Compare an unused film sample with packs before and after each stage.
Provide film labels and supplier data, photographs of unused film, seal and finished pack, video from sealing through tunnel entry, product dimensions, settings, actual speed, loading pattern and the exact point where ballooning or holes first appear.
Lancing Ltd publishes this guide to support controlled problem diagnosis. The film supplier’s specification and the machine documentation determine the approved perforation and process limits. Send film and defect evidence.
Defect review
Send unused film, reel labels, seal photographs, tunnel video, product details and the accepted result.