Shrink tunnels
Plan the shrink tunnel around sleeve material, container shape, utilities, shrink quality, output and integration with the sleeve applicator.
Shrink control
The tunnel is where the sleeve becomes the finished pack. Steam, hot-air and electric tunnels each have practical advantages depending on sleeve material, shrink percentage, container shape, moisture tolerance, energy availability and line speed.
A good tunnel specification considers temperature control, airflow or steam distribution, conveyor speed, drainage or drying, guarding, operator access and how quickly the line changes between formats.
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FAQ
It depends on the sleeve material, container shape, shrink result, available utilities and production environment. Sample testing is the safest route.
Yes, but conveyor height, footprint, utilities, guarding and downstream drying or packing should be checked first.
Sleeve material, shrink percentage, temperature profile, dwell time, airflow or steam distribution, container geometry and conveyor speed all matter.
Project support
A useful sleeve applicator shortlist starts with the real pack: container shape, sleeve lay-flat, cut length, required position, tunnel type, production speed and line layout.
Tunnel qualification
Steam and hot-air processes transfer heat differently. The correct route depends on the sleeve material, local shrink demand, container geometry, product sensitivity, site utilities and the condition required when the pack reaches downstream inspection or packing.
Electric describes an energy source rather than a finished-pack result. An electrically heated tunnel still needs a defined airflow, zone and dwell-time process, while a steam system needs steam quality, distribution, extraction, drainage and drying to be part of the specification.
Steam can provide distributed heat around complex shapes, subject to the film, pack and site conditions. Hot air provides a dry route but still needs balanced airflow and sufficient dwell time around shoulders, corners and bases. Neither route should be selected from a generic temperature alone.
Where steam is unsuitable because of moisture or site services, test the dry route on the most demanding container. Where hot air cannot control local high-shrink areas, compare a steam trial before finalising the line.
A recipe should identify the container and sleeve revision, conveyor speed, zone or steam settings, warm-up state and any cooling or drying arrangement. Keep good and faulty samples with the record.
Avoid correcting every defect by increasing heat. Wrinkles, twist and poor registration may originate before the tunnel; pack deformation, burn or splitting may indicate excess local energy or dwell.
This page covers tunnels used with shrink-sleeve labels and tamper bands. For complete product or multipack shrink wrapping in POF, PE or PVC film, use Shrink Wrapping Machinery UK or Sleeve Sealers UK.
For a complete filling, capping, sleeving, inspection and packing line, use Packaging Lines UK for the wider integration scope.
Buyer questions
No. It can be useful for complex shrink profiles, but the material, pack, moisture tolerance, utilities and sample result determine the correct route.
Electric usually describes how heat is generated. The tunnel still requires an airflow, temperature-zone and dwell-time design that must be qualified on the pack.
It provides a starting point for how the material responds. The actual container and tunnel trial is still required because local geometry changes the process demand.
Scan cooled finished packs produced at the intended process conditions and retain the artwork, film and recipe references with the result.
Condensation, pack surface, steam distribution and drying can contribute. Record the pack condition at exit and after the intended drying or cooling stage.
Record the sleeve and container, line speed, settings, warm-up condition, duration, good output, defects, stops and the measured finished-pack criteria.
Recipe qualification
A good sleeve produced once at a single setting does not show how the process will behave after warm-up, a normal stop, a speed adjustment or a change in pack condition. Tunnel qualification should identify the controlled inputs and demonstrate a repeatable operating window without deliberately exceeding the sleeve or container limits.
Steam can transfer heat around complex geometry, but it introduces requirements for steam quality, extraction, condensation management, drainage and drying. Hot air provides a dry process, but airflow balance, zone control and dwell time become central to the shrink profile. “Electric” normally describes the energy source for a heated tunnel; it does not remove the need to qualify airflow, temperature distribution and conveyor dwell.
Use the film supplier’s shrink curve as a starting input, then prove the actual sleeve on the actual pack. A steep local shrink demand at a shoulder, corner or base can move artwork or concentrate stress even when the overall sleeve material is suitable.
For multipack or product shrink wrapping rather than sleeve labels, use Shrink Wrapping Machinery UK or Sleeve Sealers UK.
Send the tunnel trial inputsProcess verification
Before changing heat or steam settings, inspect the unshrunk sleeve for cut quality, height, twist and movement. Then assess the cooled pack for local distortion, water marks, burn, barcode function, perforation and container condition.
Identify the tunnel route, warm-up state, conveyor speed, zone or steam settings, extraction, drainage, cooling and drying condition used for the approved pack. A recipe without the line and utility condition may not reproduce the result.
Use the quality-control guide for staged inspection.
Verify barcodes after shrinking and test perforations on cooled packs. Where packaging-design changes are made for recycling objectives, repeat the shrink curve and finished-pack trial rather than assuming equivalent behaviour.
See barcode verification and design-for-recycling considerations.
Shrink-process questions
The approved result depends on the complete pack, thermal route, line condition and cooled inspection point.
The sleeve and container can continue to stabilise after leaving the tunnel. A pack that looks acceptable while hot may later show movement, distortion, loose areas or closure effects. Define a consistent cooling time and handling condition before final dimensional, barcode, perforation and appearance acceptance.
Build an inspection plan →Record the tunnel type, zones or steam settings, conveyor speed, pack spacing, warm-up state, extraction, drainage, cooling, drying and the exact container, closure and sleeve revision. A recipe name without those conditions cannot explain why the same displayed setting produces a different result later.
Record tunnel settings →They influence the tunnel environment and what happens to the pack after heat transfer. Poor drainage or extraction can change steam distribution and leave water marks, while inadequate drying can affect coding, inspection, accumulation or case packing. These items should be reviewed as part of the line, not treated as accessories after approval.
Review condensation faults →Requalify when the sleeve construction, print coverage, lay-flat, cut length, container material, wall section, closure, fill condition or required finished position changes enough to alter heat transfer or shrink force. Use the previous recipe as a starting reference, not automatic proof that the new combination is approved.
Assess heat-sensitive packs →Repeatable shrink process
A useful tunnel recipe is more than a temperature set-point. It identifies the pack, sleeve material, conveyor condition, warm-up state, utilities, zone or steam settings, extraction, drainage, cooling and the finished criteria used to release the result.
Steam can transfer heat evenly around complex shapes, while hot air can suit applications where moisture is undesirable. Final selection depends on film behaviour, container sensitivity, artwork, finish and site arrangements for extraction, drainage and drying.