Aligning a four-side-seal forming collar to prevent film wrinkles
A wrinkle in a sealed bag is rarely fixed by sealing it harder. It usually begins earlier, when film is gathered and guided into its final shape. On a four-side-seal machine, the forming collar supports that transition, helping the web wrap evenly around the product path before the jaws close. If the collar is offset, tilted or working under unequal tension, small folds can become trapped in the longitudinal seal and appear as creases in the finished pack.
Shanghai Huale Industrial Co., Ltd., based in Songjiang District, Shanghai, designs four-side-seal equipment within a broader range of capsule filling, blister packaging, tube filling, cartoning, case packing, overwrapping and paper-plastic packaging systems. Its customers include pharmaceutical, food and daily chemical producers. For teams in Melbourne, Sydney and Brisbane, collar alignment must remain stable through long shifts, frequent changeovers and film lots that may differ in slip, thickness and handling behaviour.
How the forming collar shapes the film
The collar is the guide between the unwind and sealing area. It receives the moving web at a predictable angle and creates a stable channel around the product. A correct setting lets the film relax evenly, with comparable tension on both sides and no twist along the machine direction.
Wrinkles form when the film cannot travel as a smooth, flat layer. A crease may be pinched between the collar and a guide, ride up from a skewed web, or gather where one side has more tension. Once that fold reaches the longitudinal sealing area, pressure and heat can set the defect into the seal.
Three relationships matter: the collar’s centreline to the machine centreline, its face to the direction of travel, and the clearance between film and guide surface. The collar must also sit consistently with the seal jaws and product guide. Changing one relationship alters the film path, so nearby guides should not be left to compensate for a misplaced collar.
Recognising the wrinkle pattern
Before loosening an adjustment, examine where the fold appears. A crease down the centre of the longitudinal seal often points to uneven tracking or a collar that is not centred. Diagonal wrinkles usually indicate a twist in the web, while ripples near one end seal suggest a tilted collar or unequal clearance. Fine transverse ripples can come from rollers, static or inconsistent web tension.
Local conditions affect the diagnosis. Summer humidity around Brisbane can make film tackier and alter its grip over guide rollers, while Sydney sites may face rapid temperature changes as warm product moves between production and chilled storage. Melbourne’s variable conditions can produce different behaviour between a morning roll and an afternoon run. Let the machine reach its normal operating temperature before judging alignment.
Keep several sealed samples from the same film lot and compare them under steady light. Check whether the wrinkle is present before sealing, after the longitudinal seal, or only after cooling. Also review incoming film thickness, edge quality and storage history. A roll that has absorbed moisture or shifted on its core can create tension variation that looks like a collar fault.
Aligning the collar without creating new faults
Start with the machine stopped and isolated under the site’s safe-work procedure. Release web tension, remove loose film and inspect every guide in the web path. The collar face should be clean, free of scratches and undamaged. Look for a wrapped edge or a buildup of product residue, since either can shift the film sideways by a small but meaningful amount.
Use fixed machine references rather than visual guesses. Mark the collar centre at its top edge, compare it with the centre of the product path, and check that the collar is square to the direction of travel. Adjust lateral position and tilt separately, making small movements and repeating the alignment check after each one. The correct setting should not depend on tension from a dancer roller.
Alignment should be judged through the whole forming path, not at the collar alone. Follow the web through the guide, product guide and seal area, then inspect a trial bag after the machine has stabilised. A clear cartoning workflow can also help teams identify downstream compression points where a sound longitudinal seal may be bent or creased during secondary handling.
Matching symptoms to causes
A symptom-led comparison narrows the cause before anyone reaches for an adjustment. Incoming-film checks and measurements from film testing instruments can support that judgement, especially when thickness or strength varies across the roll.
| Visible pattern | Likely cause | Fast check | Practical response |
|---|---|---|---|
| Centre crease in longitudinal seal | Collar offset or uneven web tracking | Compare collar and web centrelines | Centre the collar, then inspect upstream rollers |
| Wrinkle concentrated at one end | Tilted collar or unequal guide gap | Check collar angle at both sides | Square the collar and equalise clearance |
| Diagonal fold from upper to lower seal | Twisted film or misaligned guide | Follow the web through every guide | Correct the first skewed guide in the path |
| Fine ripples across the pack | Roller buildup, static or unstable tension | Inspect roller surface and tension control | Clean rollers and stabilise web tension |
| Fold only after sealing | Jaw alignment, heat or pressure problem | Compare jaw contact and temperature | Service the sealing system separately |
| Random crease that changes by roll | Film variability or poor roll condition | Check thickness, core position and storage | Reject or isolate the affected film lot |
Work from the first guide to the last. If several checks change at once, restore a known setup and alter one variable at a time. A small, repeatable correction is easier to validate than a collection of compensating adjustments.
Checking the complete forming and sealing result
The collar controls how material enters the seal, but the seal jaws determine how that material is finished. Verify jaw parallelism, contact pressure and temperature uniformity after the collar is centred. A wrinkle that disappears when the jaws are cold may be a forming fault; one that remains after the film path is corrected needs a separate sealing investigation.
Run short trials across the intended sealing range and retain samples at beginning, middle and end of each trial. Inspect the longitudinal seal for a flat, even profile, then open a pack to check folds at the product end. Record collar position, film tension setting, machine speed and sealing conditions so the result can be reproduced during production.
For Australian facilities making therapeutic products, changes to forming geometry can affect validated process performance and should be handled within TGA expectations, GMP controls and the site’s change-control process. That includes documenting the reason, evaluating the impact on seal integrity and confirming the new setup remains capable. Food and daily chemical lines may have different documentary needs, but the same principle applies: a mechanical correction should produce an observable and repeatable outcome.
Controlling alignment between production runs
Include the forming collar in routine checks rather than treating it as a setting that only matters after a fault. At start-up, confirm the web path, clean the collar face, verify its centre reference and inspect the first sealed samples. During changeovers, remove all film from guides and check that no guide has been left in a different position from the previous product.
Keep a short setup record for each film, product and machine combination. Useful entries include collar position, tilt, guide positions, tension setting and the sample result accepted by the operator. These records help when a spare part must be fitted or an engineer travels from another site, a common issue for Australian production lines outside the major capitals.
Communication style can make the control routine stronger. Australian teams often use direct phrases such as “run it again”, “that seal is off” or “have a look at the guide”. Clear, plain language prevents a cosmetic crease from being described vaguely during a handover. When checking the line from film forming to secondary packaging, broader packaging guidance can also reveal where upstream folds are being mistaken for damage caused later in the line.
A practical setup and training routine
Train operators to diagnose from the defect pattern, then adjust from the upstream end of the web path. The goal is a repeatable setup with a documented result, not a collar position that depends on one person’s eye. Experienced staff should demonstrate the reference points, explain why each adjustment changes the film path and show how to verify the correction.
Changeover checks
- Isolate the machine and release web tension before accessing guides.
- Confirm that every guide is square, clean and in its recorded position.
- Centre the forming collar using fixed machine references.
- Make one small adjustment, run a sample and record the outcome.
Production checks
- Inspect the first sealed pack after every start-up or temperature change.
- Retain samples when a new film roll or product change is introduced.
- Log the visible defect pattern rather than recording only “wrinkle”.
- Escalate repeated faults with the material lot, settings and retained sample attached.
When a fault persists, distinguish alignment from other causes before replacing parts. Confirm that the web is not rubbing, the guide rollers turn freely and the sealing jaws are not offset. Use the symptom pattern, measured settings and retained samples to build a short fault history. That history is often more useful than relying on a general description such as “the film is wrinkling”.
A centred, level and clean collar gives the web a stable path into the jaws. When its position is checked against fixed references and verified through retained samples, production teams can prevent folds at the source and distinguish forming faults from sealing problems with confidence.