Shrink film, also known as shrink wrap, is a polymer-based material that has become an essential item in the packaging and transportation of goods.
This packaging system is therefore quite widespread in the industry due to its ease of use and the great stability and safety offered to the load both during storage and transportation.
It is possible to find shrink film in various forms, with one of the most common variations being bundling film, which is ideal to bundle several primary or secondary packaging units. Using it requires heat to be applied so that it shrinks around the target surface. This is why it is also known as heat shrink film.
It is common to experience problems in the application and results obtained with shrink film, which can lead to major complications that ultimately result in losses for the companies due to poor load stability or protection.
In this article we sum up the most common shrink film issues related to the quality or application of the product, and what can be done to avoid them.
1. Uneven edges in the shrink film roll
Uneven edges in heat shrink film (not to be confused with stretch film – shrink film does not stretch, but rather contracts to support the products it contains) may cause problems when unrolling the material. The end result can be inadequate, making it impossible to wrap the material at a straight angle and preventing the final sealing.
If a company finds uneven edges in one of its shrink film rolls, it is best not to use it and ask for a non-defective replacement. For this reason, it is essential to count on trusted suppliers that can address these issues with professionalism.
2. Defective seals
Defective seals when using shrink film can be the result of a number of causes.
First, the polymer formula can be defective, resulting in it failing to shrink as it should when applying heat. Again, in this case, it is necessary to contact the supplier to ask for a replacement.
Second, a defective seal can be the result of a poor sealing position experienced when the wrapping line is not centered on the product. In this case, it might be necessary to readjust the sealing machine.
3. Shrink film blockage
Another of the most common shrink film issues is when the different layers of the film are stuck to each other, preventing its application.
This blockage is usually the result of storing the material at temperatures that are higher than those recommended by the manufacturer. This makes the film layers melt and get stuck to each other.
In order to prevent the shrink film from getting blocked, it must be stored at the recommended temperature as per the supplier’s specifications.
4. ‘Dog ears’ in shrink film
‘Dog ears’ in the shrink film are another of the shrink film issues that might appear when using this packing method. These are parts of the film that stick out in a triangular shape (hence its name, which stems from its similarity to dog ears) at the corners of a product.
This is a problem at many levels – including aesthetics –, which should be resolved during the application process.
The main cause of these protrusions is that the film has not contracted enough during its application, leading to excess at the corners.
This problem can be caused by a number of reasons:
On one hand, it may be the result of a poor adjustment in the shrink tunnel due to the film being applied at too high a speed or using too little heat. This is why it is advisable for this protocol to be reviewed.
On the other hand, it may be caused by the use of low-quality shrink film, which causes those excesses at the corners due to a higher fragility.
It may also be caused by the characteristics of the product to be wrapped itself. For example, if it has uneven corners, ‘dog ears’ might appear during the application of the shrink film.
This phenomenon is often times accompanied by crow’s feet – wrinkles the start at the corner of packages. Crow’s feet are specifically caused at the corners of a product by an excessive use of film. Solving this problem requires reviewing the amount of film that is used, as well as the film gauge, size or width.
Solving shrink film issues
Preventing these and other of the most common shrink film issues requires carefully studying the shrink film-product relationship, studying whether the chosen combination will be able to keep the load stable and safe.
To this end, goods testing protocols such as the tilt test and the horizontal acceleration test provide companies with information on how the packaging system will react to events that take place during shipping and handling.
Implementing the various testing methods in existence will therefore be essential to address some of the shrink film issues mentioned above.
As an example, a company may determine the need to change the type of shrink film in use (to lower its gauge and prevent protuberances). The load testing process will allow it to verify that the new packaging system does not only solve this issue, but is also effective to protect the load.
It is also advisable for the company to put in place a risk prevention and maintenance program. The goal of this plan is to engage in a continuous analysis of how the shrink film is being applied in packaging processes, detecting issues before they occur and forecasting their consequences.
In summary, the objective is to establish a program involving the continuous inspection of both equipment and materials (testing, for example, the quality of the shrink film in use), and of the specific packaging processes performed.
Do you want to know more about shrink film packaging and how to guarantee its protective suitability? At Safe Load Testing Technologies we have a track record of two decades helping companies develop safe and optimized products and packages through the use of transport simulation equipment. Contact us and let’s talk about how we can help you.