Meta description: How to set shrink tunnel temperature, conveyor speed and dwell time for PE and POF shrink film, diagnose wrap defects and specify film that matches your tunnel.
Shrink tunnel settings decide whether a shrink film performs as specified. Temperature, conveyor speed, dwell time and airflow together control how much the film shrinks, how tightly it grips the pack and whether the seam holds. Buyers who change film supplier without matching these settings usually blame the film for defects caused by the tunnel.
This guide explains what each setting controls, how PE and POF shrink films respond differently to heat, how to read common wrap defects, and which film specifications to confirm before placing an order.
Table of Contents
- What Shrink Tunnel Settings Control
- How Shrink Film Responds to Heat
- Typical Setting Windows for PE and POF Film
- Matching Film Specification to Your Tunnel
- Diagnosing Wrap Defects
- Where Each Film Type Fits
- Cost and Throughput
- Common Procurement Mistakes
- Line Trials Before Ordering
- How to Choose a Supplier
- Frequently Asked Questions
- Source Shrink Film from Pefilmpack
What Shrink Tunnel Settings Control
Four variables do most of the work. Temperature sets the energy available to relax the film’s orientation. Conveyor speed and tunnel length together set dwell time, the seconds the pack spends in heat. Airflow determines how quickly and evenly that heat reaches the film surface.
A fifth variable is often overlooked: the seal. The sealer forms the bag before the tunnel, and a weak seal fails under shrink tension no matter how the tunnel is tuned.
Because these variables interact, changing one in isolation usually creates a new defect. Raising temperature to tighten a loose wrap, for example, can burn through thin film at corners while the real problem is low air velocity.
How Shrink Film Responds to Heat
Shrink film is stretched during manufacture and frozen in that stretched state. Heat releases the memory, and the film contracts toward its original dimensions. The amount of contraction is the shrink rate, expressed separately for machine direction and transverse direction.
Orientation also creates shrink force, the tension the film applies to the pack as it cools. High shrink force pulls a bundle tight but can crush light cartons or distort trays. Low shrink force protects fragile contents but may leave slack film on heavy items.
POF film, a polyolefin structure usually built from PP and PE layers and biaxially oriented, shrinks at a lower temperature with moderate force. PE shrink film is thicker, develops higher force and needs more heat. Cross-linked POF grades tolerate a wider temperature window, which matters on tunnels with uneven heat.
Typical Setting Windows for PE and POF Film
| Parameter | POF heat shrink film | PE shrink film |
|---|---|---|
| Tunnel air temperature | Lower range, commonly around 140–160 °C | Higher range, often above 160 °C |
| Dwell time | Short to moderate | Longer for the same pack |
| Shrink force | Moderate | Higher |
| Typical gauge | Thin, commonly 12–25 micron | Thicker, commonly 40 micron and up |
| Best load type | Retail multipacks, cartons, trays | Heavy bundles, industrial packs, hoods |
| Main risk | Burn-through at high temperature | Incomplete shrink at low temperature |
These ranges are industry practice, not fixed values. Tunnel design, airflow pattern, pack mass and film grade all shift the correct setpoint, so treat the table as a starting point for a trial rather than a recipe. Requirements may vary by application, market and applicable standard.
Matching Film Specification to Your Tunnel
- Tunnel length and belt speed determine the dwell time available. A short tunnel running fast needs a fast-shrinking film, not a lower temperature.
- Shrink rate in both directions, checked against pack shape. A tall carton needs more transverse shrink than a flat tray.
- Shrink temperature window: a narrow window is efficient on a stable tunnel and unforgiving on an old one.
- Gauge, balanced against corner sharpness. Thin film saves cost until corners puncture it.
- Center-folded or tubular format, matched to the sealer and the pack geometry.
- Perforation or venting, needed where trapped air would otherwise balloon the wrap.
- Haze and gloss, where barcodes or print must remain readable through the film.
- Seal strength, because the seam carries the shrink force during cooling.
Send the tunnel make, tunnel length, belt speed range and pack dimensions with the enquiry. A film quoted without those details is a guess.
Diagnosing Wrap Defects
| Symptom | Likely cause | First adjustment |
|---|---|---|
| Loose, sagging wrap | Temperature low, speed high or airflow weak | Confirm dwell time before raising heat |
| Holes or burn-through at corners | Temperature high, dwell long or gauge thin | Lower temperature, then shorten dwell |
| Dog ears at pack ends | Excess film or unbalanced airflow | Reduce film width or balance top and bottom air |
| Uneven shrink, top versus bottom | Airflow imbalance in the tunnel | Check blower settings and nozzle condition |
| Seam opens in the tunnel | Weak seal, not a tunnel fault | Review seal bar temperature, pressure and time |
| Film sticks to printed cartons | Surface too hot for the coating | Reduce temperature and increase belt speed |
Work through one change at a time and keep the pack constant. Two simultaneous adjustments make the result unreadable, which is how a line ends up running on settings nobody can explain.
Where Each Film Type Fits
Beverage and canned goods multipacks
Heavy packs need holding force. PE shrink film or a high-force POF grade keeps cans and bottles together, with perforation where condensation must escape.
Corrugated and boxed bundles
POF suits printed cartons because low shrink force preserves print quality and does not crush corners. Thicker PE film is reserved for heavy or rough-handled bundles.
Retail-ready and e-commerce packs
Clarity and gloss drive the choice, together with a clean seam. A narrow shrink window is acceptable here because retail packs repeat the same dimensions. Bundle patterns for these formats are set out in this guide to POF and PE shrink film for retail multipacks.
Industrial components and hardware
Sharp edges puncture thin film. Higher gauge plus corner board costs less than the reject rate from repeated burn-through.
Cost and Throughput
Film cost per pack is the product of film used and price per kilogram, but the tunnel drives both terms. A film that shrinks fully at lower temperature reduces energy use, and a wider processing window reduces rejects and stoppages.
Downgauging is the fastest saving and the fastest way to create defects. Moving from a heavier to a lighter gauge on the same tunnel usually requires more airflow and a tighter speed setting, not simply a higher temperature.
Count rejects, not just film consumption. A line rejecting a few percent of packs because of burn-through or open seams is spending more on rework and labor than it saves on a cheaper roll. Compare total cost per acceptable pack across a full shift, including startup waste.
Common Procurement Mistakes
- Ordering shrink film without stating tunnel type, length and belt speed.
- Assuming a POF film will run on settings developed for PE film, or the reverse.
- Buying on price per kilogram while ignoring gauge consistency, which changes shrink behavior roll to roll.
- Ignoring fold width, then losing film at both edges of every pack.
- Skipping perforation on packs that trap air.
- Changing film and seal parameters at the same time, leaving no way to identify the cause of a defect.
- Not confirming that the quoted shrink rate refers to the same test method you use internally.
Line Trials Before Ordering
Run a trial on your own tunnel with production packs, and record settings, belt speed, pack weight and reject count. Then repeat on a second day to see whether the result holds when ambient conditions change.
Ask the supplier for the film’s shrink rate and gauge tolerance, and check the roll face and winding tension on arrival. A roll wound too soft will feed unevenly and produce inconsistent wrap regardless of tunnel settings.
Where shrink rate is quoted, confirm the method. Free shrink is commonly measured with a method such as ASTM D2732, and tensile properties with ASTM D882. Those figures describe the film; they do not predict how your tunnel will run it.
How to Choose a Supplier
Ask which film structures the supplier actually produces, and whether it can supply both POF and PE grades. A supplier who understands both can advise on the trade-off instead of pushing whichever grade is in stock.
Confirm control over gauge and orientation, since both determine shrink consistency. Then check practical support: sample rolls at production width, recommended starting settings, and a stated tolerance for thickness and width.
Warning signs include shrink rate quoted without a test method, refusal to supply a production-width sample, and a price well below the market for the stated gauge and structure.
Frequently Asked Questions
Can I run POF film in a tunnel set up for PE film?
Usually, but only after lowering temperature and shortening dwell time. POF shrinks at a lower temperature, so PE settings will burn through it.
Why is my wrap tight at the ends but loose in the middle?
Airflow is reaching the pack edges before the center, or dwell time is too short for the pack mass. Check blower balance and slow the belt slightly.
Does a longer tunnel always give better shrink?
No. Longer dwell helps heavy packs, but overexposure causes sagging, distortion and seam failure. Match dwell to film and pack weight.
What gauge should I start with for retail cartons?
Thin POF grades are common for cartons, with gauge increased only where corners or handling demand it. Trial two gauges and compare rejects per thousand packs.
Can shrink film be customized?
Width, fold width, thickness, perforation, core size and roll length are made to order, subject to minimum quantities. Printing is available on some formats.
How should shrink film be stored?
Cool, dry, out of direct sunlight and away from heat sources. Film stored near a tunnel or in a hot warehouse can shrink on the roll.
Source Shrink Film from Pefilmpack
Weishan Litong Packing Material Co., Ltd. supplies PE shrink film and POF heat shrink film alongside PE stretch film, cling film, protective film, silage film, BOPP packing tape and PET strapping band. Width, fold width, thickness, perforation, core size and roll length are made to order, with OEM labeling for distributors. Because both film families are supplied, we can advise which grade suits a given tunnel and pack rather than quoting a single structure. Film is inspected before shipment and packed for sea freight. Send your tunnel details through the contact page.
Request a quote: tell us pack dimensions and weight, tunnel type and length, belt speed, film format, thickness, fold width, perforation, roll length, quantity and destination port.
Recommended Images and Alt Text
| Image Placement | Image Description | Recommended File Name | Recommended Alt Text |
|---|---|---|---|
| Hero | Shrink-wrapped cartons leaving a tunnel | shrink-tunnel-wrapped-cartons-exit.jpg | Shrink-wrapped cartons leaving a heat shrink tunnel on a conveyor |
| Production | POF film bubble or tenter frame during biaxial orientation | pof-shrink-film-orientation-line.jpg | POF shrink film line during biaxial orientation of the film web |
| Controls | Tunnel control panel showing temperature and belt speed | shrink-tunnel-control-panel-settings.jpg | Shrink tunnel control panel showing temperature and conveyor speed settings |
| Comparison | POF and PE shrink film rolls side by side | pof-vs-pe-shrink-film-rolls.jpg | Rolls of POF and PE shrink film shown side by side for comparison |
| Application | Shrink-wrapped beverage multipack on a pallet | shrink-film-beverage-multipack.jpg | Beverage multipack wrapped in clear shrink film ready for distribution |
| Inspection | Operator measuring film thickness on a roll | shrink-film-thickness-inspection.jpg | Quality inspector measuring shrink film thickness with a handheld gauge |
| Packing | Shrink film rolls wrapped and palletized for export | shrink-film-export-packing.jpg | Shrink film rolls wrapped in protective film and palletized for export |