By: David Roberge on June 12th, 2019
Common Shrink Wrap Problems and How To Solve Them
Equipment | Packaging Materials | The Business of Packaging | Technical Service and Support | Plant Performance | Food Packaging
Shrink wrapping is an easy process that only requires two things: the right kind of plastic wrap and heat. With just a roll of shrink wrap and a heating source, you can waterproof, weatherproof and tamper proof just about anything you have. Since there is no restriction on size to shrink wrap items, you have a way to protect even your bulkiest of items. But even this great packaging solution has a few potential hiccups.
There are a wide variety of issues that can occur when shrink wrapping products using shrink film. In this post, we will walk through common shrink wrapping issues as well as solutions to them. Most of these issues are pretty common and easy to resolve by adjusting machine settings without having to seek technical service.
Dog Ears On Shrink Wrap
These are typically seen around the corners of packages in the grocery store. Dog Ears are triangular protrusions of the film on the corners of a package and as their name suggests, they resemble a dogs ear. These ARE very common, and happen for a variety of reasons.
Triangular “ears” of excess shrink wrap are signs that there was insufficient shrinkage of the film, causing the corners to not shrink down enough. Here's how to solve for it:
- Step one is to assess the heat of your shrink gun or shrink tunnel. Make sure it is putting out enough heat to properly wrap the package while being cool enough to not damage your product.
- Next check the size of your shrink film or tubing. Utilizing a larger film width than necessary can result in dog ears appearing on the corners of your finished goods. See if you can wrap the package with less film by reducing film width.
- They may also arise more often when using lower-quality films. Using PVC film results in dog ears more commonly, because it is more brittle than polyolefin after being heated and may tent at corners. Polyolefin film is generally more expensive, but this is because it is of higher quality.
- You should also check the size and shape of your packages too. If the shapes of your products are irregular or they have abnormal corners, this can result in dog ears as the item goes through your heat tunnel.
Dog ears aren't out of the ordinary, in fact if you walk into any retail store you will find them. It comes down to how big they are and how important product appearance on the shelf (or off) is to your brand.
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Crow’s Feet On Shrink Wrap
Going hand-in-hand with dog ears, crow’s feet are wrinkles extending from the corners of your packages. Many times when solving for dog ears you will solve for crows feet.
Crow’s feet specifically are caused by excessive film on the corners of the product. Using a smaller shrink wrap or shrink tubing width or length may help.
Another cause is not heating the package enough. Make sure your heating element is producing enough heat to adequately shrink the film uniformly across your product. If you are manually shrinking with a shrink gun, an extra run across the area with the crow's feet may remedy the issue.
Fish Eyes On Shrink Wrap
Fish eyes (yes, there are a lot of animal names) are round or oval patterns in the plastic on a package that was shrunk poorly. These look far worse than dog ears and come off as unprofessional and sloppy.
Fish eyes are caused by a lack of heat. Check your heating element. Proper regular maintenance of your packaging line can greatly reduce the amount of damaged goods you see.
They are also caused by bad air velocity. If your heat source is not pushing enough air when applying heat, the wrap doesn’t shrink consistently.
Perforations in the wrap can cause them, too. Slow down your conveyor speed to minimize this effect, and allow the heat to apply fully.
Angel Hair On Shrink Wrap
These are very thin strands of melted plastic that stretch from the product and the sealed part of the film. This is usually a minor issue, but can still be an inconvenience.
Angel hairs are caused by the sealing wire or seal bar not being hot enough. The wrap doesn’t have time to cut completely, and the wrap stretches off the wire.
Make sure your sealing wire is working properly, and also check your clamp pressure. If the clamp is uneven, some film cuts well and the rest doesn’t.
Angel hairs in your shrink packaging can also be caused by your conveyor speed. If the sealer is opened too early, it can cause an incomplete sealing cycle. Using quality machinery can greatly impact a good shrink seal.
Ballooning Shrink Wrap
Shrink wrap ballooning happens when the shrink film is exposed to hot air after sealing. The air inside of the bag expands and causes the shrink film to balloon.
This can be addressed by using film with vent holes, also known as pre-perforated film. This film comes with very small holes throughout the entire roll of film that allow air to escape as the film is shrink around the product. They are virtually unnoticeable once shrunk. Using pre-perfed film is product dependent. Check with your supplier if you want to learn more about perforated film.
Keep excess air out of the package as it’s being wrapped as well, and if using vented film, make sure the vents are properly positioned to allow the air to escape.
Splitting Seals On Shrink Wrap
Bad seals are probably the most costly shrink wrap issue, and if you are experiencing this problem, address it immediately. Split seals can result in damaged products, tampering measures being triggered, and even lost product during shipment.
Split seals can have a variety of causes. One may be that your film isn’t thick enough. Depending on what you are packaging, a thicker film is an easy way to address bad seals, but can increase your costs.
It might be a bad roll of film; make sure it looks how it should without unnecessary perforations or holes. Or, make sure the perforations are there if your product requires them.
Go right to the source and make sure it is functioning properly. Clean your sealing wire and make sure it is not too hot or not hot enough. You should check your clamp too to make sure it is applying pressure evenly.
Shrink wrap is a great packaging solution, but it can sometimes be finicky with all the different variables that come into play. For the most part these issues are all fairly easy to remedy. There are even programs that some businesses are using to correct film distortion in a new way, like iC3D and Unilever.
The size of the package, speed it’s being wrapped, and differences in formulations of shrink film can all interfere with the professional look of your wrapped packages. But with a few simple tweaks to your system, you can avoid these common shrink wrap problems and keep your packages looking perfect.
About David Roberge
I am grateful for my 9 years as part of the outstanding Industrial Packaging team. I was able to hang out with some of the most knowledgeable folks in the packaging industry. I feel even luckier that I was able to share that knowledge with you. I love learning, hiking, and growing people and teams both personally and professionally, and helping companies grow better.