DECIPHERING THE WORLD OF SHRINK TUNNELS

Shrink tunnels are crucial pieces of equipment used in commercial packaging and labeling. They get used for varied applications, and it is important to find the right one to get the best results. Factors that determine your shrink tunnel choice include the type of film you are using, the shape and nature of your product, its contents, if any, etc.

What are Shrink Tunnels?

Shrink/heat tunnels work with steam as well as hot air. You can think of a shrink tunnel as an enclosed metallic space fitted with a conveyor belt. Different objects pass through the belt, and heat is applied to the passing objects to achieve specific results. It can include covering an object with a sleeve or shrinking a film around a product precisely. The two main factors to consider here are the speed at which the conveyor belt moves and the period for which heat will apply to the objects.

Different Types of Shrink Tunnels, Pros, and Cons

There are three main varieties of shrink tunnels available for commercial purposes.

1. INFRARED TUNNELS

Often used with hot air shrink tunnels, infrared tunnels fitted with infrared bulbs emit the rays to create a warming effect only on the surface of the packaging containers. It, in turn, helps to complete various shrinking applications. An apt example of infrared tunnel usage is shrinking seal bands on products.

Infrared Tunnels are known for

• Being energy efficient as they only heat the surface of the objects
• Transferring optimum heat almost instantly
• Low overall costs

However, when using an infrared tunnel

• Full exposure to all parts of the object is a must otherwise the obstructed area will have shrinkage issues
• There are limitations in maintaining different wavelength bands
• Not suitable for applications where the shrinkage percentage is high

Infrared Tunnels are the least popular choice as it generates high heat which can sometimes cause uneven shrinkage. A further challenge with the high temperatures is the difficulty with empty containers. It’s very complicated to shrink a sleeve on an empty PETG container.

2. HOT AIR SHRINK TUNNELS

As the name suggests, this tunnel uses hot air to create heat and shrink the packaging sleeve onto the product smoothly and uniformly. Since heat gets blown in this type of tunnel, we can easily choose the direction of the heat and its application.

Hot Air Tunnels are known for

• Ability to target and customize the heat and airflow
• Different temperatures can be maintained
• Low overall costs

However, when using a hot air shrink tunnel

• Good ventilation is a must while using this tunnel
• A rotary puck type tunnel helps in providing even shrinkage

3. STEAM SHRINK TUNNELS

Ideal for shrink applications, these tunnels use piped steam to create a heating effect rather than hot air. As the steam gets introduced into the tunnel and heat is generated, it produces the shrinking effect of sleeves onto the desired product. Since such tunnels work on steam, they need a supply of water.

Steam Shrink Tunnels are known for

• Versatility in their shrinking abilities
• Consistent and uniform heat distribution
• Suitability for working with packaging containers with a contoured body

However, when using a steam shrink tunnel

• You need an external source to generate heat
• Objects passing through the tunnel must be dried before packing
• There is a possibility of corrosion
• Certain shrink materials are not supported
• The tunnel length needs to be longer compared to other shrink tunnels
• It requires more investment

Dry Vs Wet Steam Tunnel

 Although ‘wet’ and ‘dry’ are both steam, it’s essential to choose the right type to ensure the best results, and avoid causing sleeving problems.  An understanding of the difference and performance of each will make it easy to determine which is the best solution for your product.

Self-Generating Steam Tunnel

Most steam tunnel require an external source of steam like a Boiler, but you also have an option of a Steam tunnel that generates its own steam.

Possible Complications You Can Expect During Shrink Sleeving

Packaging using shrink sleeves is a process requiring the right conditions to get the optimum output. Several factors can have a bearing on the results.

Container Shape, Curves & Taper: A cylindrical-shaped container is probably the most straightforward to go through the shrink-labeling process. However, if the container shape is square or something else with vertical edges, it may be more complex to ensure uniform shrinkage. Distortions are possible. The same goes with tapering shapes, curves, and varying diameters of the container where maintaining an even shrinkage can be challenging.

Container Material of Construction: Container materials like Glass, Tin, Aluminium, PP, HDPE, and PET is a critical variable in the shrink result and the choice of shrink tunnels is completely dependent on the shrink tunnel. No one type of shrink tunnel is perfect for all types of containers. This is important to know when selecting the tunnel.

Material Choices: The material you select for shrink sleeve development also affects the results you can expect. While PVC shrinks at low temperatures with ease almost in a uniform way, PETG does not shrink uniformly, and there are more chances of distortions taking place. However, it is more supportive of the environment than PVC.

Surface Finishes: The type of surface embellishments used, matte or glossy finish, and embossed design on the labels, all can have a bearing on the way the label gets shrunk.

Weather: Different ambient weather can give different shrink results on certain types of containers or shrink film. This factor needs to be identified if applicable for your container so that probable shrink tests can be done.

Which Shrink Tunnel is Suitable for You?

Since several factors come into play while choosing the ideal shrink tunnel for you.

• Is your product sensitive to heat?
• Is distortion of graphics a major factor in your decision
• Shrink result quality
• The material of sleeve you use
• The shape of the container
• Budget

It is not recommended to make a generic choice. Instead, ensure that you find a shrink sleeve supplier who discusses your typical shrink labelling needs and then recommends the best option for you. A good technique is to test a few sample sleeves and get the prototype to see the results before purchasing the final one for your business.

CLOSING THOUGHTS

Shrink tunnels are crucial in producing good shrink-sleeving results for your product packaging needs. Hence, knowing the different options available and choosing the one that is best suited to your needs is a crucial step.

Do you want an expert opinion on selecting the best shrink tunnel for your packaging needs? Then I encourage you to book a discovery call with me at www.chetan-jain.com.