Jan. 23, 2025
No matter if you're in food service or consumer packaged goods, shrink wrap is an essential packaging solution.
It offers customization, efficiency, and reliable protection for your products during transit. As a key advancement in manufacturing, shrink wrap has revolutionized packaging operations.
However, if your shrink wrap system isn’t running at peak performance, you could be losing valuable time, money, and resources. Worse, poor shrink wrap quality may even impact your brand’s reputation.
Most shrink wrap challenges stem from three key factors: temperature, time, and pressure. Keep reading to evaluate your shrink wrap process and identify solutions to common equipment or production line issues.
Shrink wrap serves multiple purposes—from protecting products against moisture and dust to enhancing retail appeal and reducing environmental impact. However, certain issues can arise, affecting efficiency and profitability.
Before diving into troubleshooting, it’s important to determine whether the problem stems from the machinery or the shrink film itself.
1. Perform a Quick Test: Start by creating an empty shrink bag using your current settings.
2. Inspect the Seals:
- If the seals are intact, the issue may be an incorrectly sized shrink film.
- If the seals are weak or faulty, the problem likely lies with the machinery, requiring further inspection and adjustments.
The most common culprit behind shrink wrap failures is improper temperature—whether too high or too low. However, issues can also result from a combination of temperature, pressure, and time.
Read on to identify key problems and discover solutions to optimize your shrink wrap process.
Temperature-related issues can manifest in various ways.
To determine the optimal temperature for your sealer, start by setting it to the lowest possible temperature where the film no longer cuts. Gradually increase the temperature in 5°F-20°F increments until you achieve consistent seals at the desired line speed.
When layers of flat film fuse together, it’s often due to excessive storage temperatures. Store film in a controlled environment to prevent this issue.
Torn, uneven, or incomplete seals indicate low seal temperatures. Increase the heat in 25°F increments until you achieve clean, sharp seals.
Dwell time—the duration the seal jaws remain closed—varies based on temperature. If sealing takes too long, the temperature may be too low. Adjust accordingly.
Thin, hair-like strands between the sealed shrink film and the sealing mechanism result from insufficient heat. Increase the temperature for a cleaner seal.
Excessive heat causes smoking and polymer residue on sealing pads. Worn pads can also contribute to buildup. Reduce sealing head pressure and ensure proper alignment.
Overheated film can cause whitening or burn holes. To prevent this, increase conveyor speed, lower tunnel temperatures, and adjust airflow. Also, ensure the film does not touch tunnel walls or ceilings.
Brittle seals with pinholes suggest excessive seal temperatures, leading to film crystallization near the seal. Look for parallel white lines about 1/16” from the seal and adjust the temperature as needed.
When hot air expands inside the shrink bag, it inflates the film. Use pre-perforated shrink film to allow air to escape as the film conforms to the product.
Wrinkles or sags at package corners indicate improper heat distribution. Slow the conveyor, increase tunnel temperatures, reduce air evacuation, and redirect airflow. Adjust perforation placement or quantity as needed.
Round or oval patterns on the shrink film surface indicate inadequate heat. Increase tunnel temperature, slightly speed up the conveyor, and reduce airflow. You may also need to use less excess film.
Electrostatic discharge (ESD) can cause film tracking, tension problems, or matted film. Check for static by holding a film piece near a conductive surface—if it’s attracted, static is present.
- Ensure equipment is grounded using three-prong plugs.
- Connect the machine frame to a grounding source (e.g., metal pipe or drain).
- Roughen polished surfaces with sandpaper to reduce static buildup.
- Use static eliminators if needed.
When timing isn’t properly aligned with machine settings, certain issues commonly arise during shrink wrapping.
To minimize "dog ears" at the corners of the seal, ensure perforations are strategically placed to improve air evacuation. Reduce the bag size, slow the conveyor speed, and increase both the air velocity and tunnel temperature. Additionally, redirect the tunnel’s airflow towards the package ends.
If the shrink film is damaging products, the issue may lie in tunnel settings or excessive film force. Try allowing more film around the package, increasing the conveyor speed, lowering the temperature, and reducing airflow. If the problem persists, consider switching to a lower-energy film with a gentler shrink force.
To prevent seal failure, reduce film tension near the sealing area and ensure air flows through various perforations. You may also need to increase the size of the shrink bag. Check the tunnel’s components: make sure air intake screens are clear of melted polymer, heater banks are functioning correctly, blowers are oriented properly, and temperature controls are operating as they should.
Pressure is a key factor when it comes to adjusting your machinery. Improper seal pressure or tension can cause common shrink wrap problems.
If you’re seeing any of the following issues, pressure is likely a factor:
Seal jaw pressure is perfected when machines are built, but worn parts or misaligned jaws can affect it over time. As a test, put a white piece of paper in the seal area and engage the jaws to lower and seal. If the pressure is even, it should create a continuous, uniform line on the paper. If the line appears dotted or has gaps, the sealing jaws may require maintenance. Additionally, if the lines in the film clamp area are not parallel, one of the film clamps may be misaligned and making uneven contact with the pad.
Split seals may result from using film that is too thin or from a defective roll. Inspect the film for unnecessary perforations or misplaced holes. Ensure the sealing wire is clean and set to the correct temperature. Additionally, check that the clamp is applying even pressure.
In semi-automatic and automatic L-bar sealers, improper cross-seals can occur due to excessive tension. To resolve this, increase the bag length or add more spacing between packages to reduce tension in the cross-seal area.
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