Application testing
Use a representative trial to assess total tunnel exposure, product condition, pack materials and cooling rather than relying on one temperature setting.
Direct answer
Direct answer: A heat-sensitive product can be considered for shrink wrapping only after the product, container, label, adhesive, coating and internal components have been assessed under the proposed tunnel cycle. The tunnel air setpoint is not the same as the temperature reached by the product. Dwell time, airflow, starting temperature, conveyor contact and cooling all affect exposure.
A short pass through hot air may be acceptable for one construction and damage another. Vulnerable effects include softening, warping, label lift, ink or varnish change, loss of adhesive performance, product melting, condensation, pressure build-up or cosmetic marking. The buyer should identify the failure that must be prevented and provide the most vulnerable representative samples.
| Heat-sensitive element | What to observe | Trial evidence |
|---|---|---|
| Outer container or carton | Warping, softening, scuffing, gloss change or loss of flatness. | Cooled samples compared with an unprocessed control. |
| Labels, inks and adhesives | Lift, bleed, movement, wrinkling or reduced barcode readability. | Normal inspection and scan checks after cooling. |
| Product or internal component | Temperature-sensitive change, movement, pressure or functional effect. | Buyer-defined acceptance method and competent product review. |
| Cold or chilled pack | Condensation, uneven film response or altered starting condition. | Samples at the real production temperature and environment. |
Direct answer: A product is heat-sensitive when any part of the product or pack can be changed unacceptably by the total tunnel exposure.
The vulnerable element may be hidden inside the carton or may be a label, adhesive or surface coating. The product owner should define the permitted condition and the test method rather than relying on a general description such as “low heat”.
Direct answer: No. A shorter dwell time can reduce exposure, but it may also leave the film loose and can require other changes that alter airflow or surface heating.
The correct balance depends on film response, product geometry and the required finish. If a safe process window cannot be demonstrated, a different film, tunnel arrangement or non-shrink packaging route may be more appropriate.
Direct answer: Test the most vulnerable construction, the largest thermal mass, the lightest pack and any product supplied at a different starting temperature.
Include the real labels, adhesives, coatings and inserts. Where the product condition cannot be represented safely, the buyer should provide an approved test method or specialist evidence before machinery suitability is confirmed.
Direct answer: A non-shrink route should be considered when the required film recovery cannot be achieved without unacceptable product, label or container change.
Alternative routes may also be preferable when the pack cannot release air, cannot remain stable through the tunnel or does not need a tight presentation finish. The decision should follow a representative trial rather than repeated increases or reductions in heat without a defined acceptance criterion.
Scope note: Lancing can review machinery and trial requirements, but the product owner remains responsible for defining product limits, safety, quality and any sector-specific validation.
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