Tunnel sizing guide
A physical fit is only the starting point: usable clearance, conveyor support, exposure, thermal load and cooling must all suit the production pack.
Direct answer
A shrink tunnel aperture should clear the widest and tallest loose-film pack in its real running orientation, including movement, guides and film ballooning, while still allowing controlled airflow. Heated length must then provide enough exposure at the required actual conveyor speed and thermal load. Conveyor support, distributed weight, product heat tolerance, ventilation and cooling are part of the size decision—not separate afterthoughts.
| Input | Why it changes the tunnel | Evidence to provide |
|---|---|---|
| Loose wrapped width and height | Defines the physical envelope before the film has collapsed | Maximum product dimensions, film overlap, side fins, projections, photographs and running orientation |
| Pack base and weight distribution | Changes conveyor support, transfer stability, load and possible marking | Complete weight, contact footprint, centre of gravity, tray or pad and the least stable format |
| Required accepted output | Connects actual speed, heated length, spacing and thermal recovery | Good packs per production period, pitch, gaps, restart pattern and product mix |
| Film and shrink curve | Determines the usable heat, airflow and exposure window | Supplier, code, material, gauge, perforation, shrink data and intended reel |
| Product thermal load | Cold, dense or closely spaced products absorb heat and can alter recovery | Product temperature, contents, pack density, highest load and heat-sensitive parts |
| Cooling and next operation | Warm film can move or distort before it reaches an accepted handling state | Discharge length, guides, accumulation, labelling, case packing, lifting or pallet handling |
Dimensional and thermal sizing
A tunnel can be physically large enough and still fail the production duty if exposure, airflow, support or recovery is wrong.
Use the wrapped pack before shrink, not only the bare product or cooled result. Allow for loose film, product movement, guide position and the practical clearance needed to avoid contact. Excessive unused space can also make airflow control more difficult, so bigger is not automatically better.
For a fixed speed, a longer heated zone generally provides more exposure, but the useful result still depends on airflow, temperature, film, loading and product heat absorption. A higher set temperature is not a safe substitute for insufficient or poorly distributed exposure.
Belt width is not always the same as usable pack width. Guides, structure, film movement and transfer gaps reduce the practical envelope. Check load distribution, contact marking, product stability and whether the conveyor allows heat to reach the film where required.
The film can continue to settle after leaving the heated zone. The line needs enough support and cooling before compression, tight guides, labelling, case packing or pallet handling. A short discharge can undo an otherwise acceptable tunnel result.
Record the maximum width and height with production film applied in the intended orientation.
State good packs per period, spacing, gaps, restarts and the heaviest expected tunnel loading.
Confirm belt or roller duty, actual speed, heated length, airflow and product heat limits.
Inspect after full cooling and test the first downstream transfer, guide, stack or lift.
Verified Lancing references
These values are already published on the corresponding Lancing machine pages. They support shortlisting but do not replace usable-clearance, film and production trials.
| Machine route | Published data | What still needs confirmation |
|---|---|---|
| LU-BSP6040 heat tunnel | Furnace 1800 × 600 × 400 mm; conveying speed 0–15 m/min; maximum conveyor load 50 kg | Usable wrapped-pack clearance, load distribution, actual dwell, electrical supply, ventilation and sustained thermal loading |
| LU-SPL6 wrapping route | Tunnel reference 1800 × 750 × 400 mm; 600 mm conveyor belt; POF and PE listed | Product orientation, loose film, guide clearance, seal quality, compressed air, tunnel recipe and downstream cooling |
| LU-SPL4 bottle bundle route | Maximum package 400 × 120 × 330 mm; payload up to 20 kg; 0–6 packs/min | Bottle-group stability, filled-pack weight, film, collation, transfer, cooling and sustained accepted output |
Buyer questions
A physical fit is only the first acceptance condition.
There is no universal clearance figure. The loose-film pack must enter without contact or snagging, allow expected movement and preserve effective airflow. The required space depends on film ballooning, guides, product stability, conveyor support and the selected tunnel design, so it must be confirmed on the final configuration.
Not necessarily. Side structure, guides, film movement, practical clearance and product stability can reduce usable width. Check the wrapped pack against the final machine arrangement rather than treating the published belt width as a guaranteed processing envelope.
A longer heated zone can support more exposure at a given speed, but accepted output also depends on airflow, temperature, film, product thermal load, spacing, recovery and cooling. The complete process should be proven under sustained representative loading rather than inferred from length alone.
Define a realistic future envelope with dimensions, weight, film, pack pattern and output. Deliberate reserve in aperture, conveyor and controls is useful; unrestricted oversizing can make today’s smaller packs harder to support or heat consistently. Confirm both current and credible future formats.
Yes. A heat-sensitive product may need a wider process window, controlled airflow, suitable heated length, lower thermal intensity, shielding or another heat route. Provide filled production samples, labels, closures and contents so the film can be shrunk without exceeding the pack’s accepted condition.
Send the loose wrapped dimensions, weight and base footprint; product photographs; intended film; required good-pack output; product temperature; available services; conveyor direction and height; upstream equipment; cooling space; and the first downstream handling operation. Include representative samples and an approved pack where possible.
Published dimensions are screening data. The final usable aperture, conveyor duty and accepted thermal process depend on the supplied configuration, production film and representative pack trials.
Tunnel sizing review
Send the physical envelope, film, output, weight, product temperature, services and cooling route so the tunnel can be screened against more than nominal dimensions.