What film should I use?
If you’re shrink wrapping big stuff like pallet loads or furniture, you’ll need fairly hefty polythene film. This is available in several formats on a wide roll, which is usually held on a mobile roll dispenser
Folding the film before it’s wound onto the roll means it takes up less room but unfolds to two or three times the width. This gives you a flat sheet of film.
Gusseting reduces the roll width but when removed from the roll the film becomes a seamless tube with a circumference approximately four times the unrolled width. This means that you can place it over whatever you’re wrapping and as the film shrinks it’ll pull it all together.
If you’re consistently wrapping uniform-sized pallet loads, this might be the best option for you. Imagine a clear plastic bag the size of a loaded pallet. Pop it upside-down onto the pallet and shrink it, and you have a totally sealed protective covering that won’t sag or unwind.
If you want to shrink wrap smaller stuff, there’s basically two options. These come in much narrower rolls and thinner film, so of course you get a lot more linear metres on a roll.
This is the original shrink film for retail packaging and is still popular because it’s the cheaper option. And it’s also the film with the highest clarity, which is good for giving products a high class finish. It’s thin and pliable before use but becomes more brittle once shrunk.
It also shrinks faster and at lower temperatures, but the chloride in the PVC means it’s unsuitable for direct contact food use.
Newer and more expensive than PVC, polyolefin is the more popular choice for several reasons. It’s more forgiving when stored at higher or lower temperatures, where PVC would stick together, wrinkle, harden or become brittle.
It’s also FDA approved for direct contact food packaging and works well in cold storage. While it may not be as clear and shiny as PVC when new, it doesn’t discolour or become brittle with age.
And it that’s not enough, it’s also more tolerant when wrapping irregular shapes and bundling several products together.
What equipment do I need to shrink wrap?
You’ll probably need a floor-standing dispenser if you’re using film products. This will keep the film off the floor away from dust and damage and make it a whole lot easier to unwind from the roll.
You’ll need a heat shrink gun. In theory, you could get by with an electrical heat gun but the cable will always be in your way and a gas powered gun will do a far better, far faster job. It’s also a good idea to have a gas cylinder trolley as this will not only help you move the cylinder around but will provide safe storage for the gas gun.
A large metal spatula (the sort you use on a barbecue, with a wooden handle) will help you to form the heated film for a neat, compact finish without getting burnt fingers. Heat the spatula blade before applying it to the film and you’ll be able to make a neat lap seal.
If your volumes are low you may find that a basic L-bar sealer, film unroller and an electrical hot air gun will be enough and these can be bought as a complete kit or as separate items. A impulse sealer with an integral cutter will allow you to trim the film neatly off the roll with a uniform edge.
On the subject of the hot air gun, avoid the sort you can pick up at hobby shops and DIY stores; you’ll need an industrial-quality heat shrink gun like a Ripack® R3000 or R2200 that will cope with extended use.
You’ll need to choose which film will be best for you – we’ve covered that earlier in this article – and when you look at it you’ll see that it comes on the roll as a double layer film with a fold along one edge. An L-bar sealer creates a seal along the film’s leading edge so that when you insert the product between the two layers of film, two of its four sides are already sealed.
Close the L-bar sealer and it will seal the other two edges, leaving behind a bit of scrap plastic along the front edge and a sealed edge for the next pack. Carefully use the hot air gun to apply heat to the film, constantly turning the pack so that the film shrinks evenly.
If the film splits at the sealed edges, check how well it’s being sealed as dirty sealing wires too little or too much heat and taking the pack off the sealer too quickly can all be to blame. If you get holes appearing at other points of the film you’re probably being too aggressive with that heat gun. try again, and this time keep the gun moving over the film and don’t hold it too close. You’ll soon get the hang of it.
If your volumes are higher you’ll probably want to consider something more automated as this will be quicker and give more consistent results. These options still use the basic principle of an L-bar sealer and hot air but with a bit more ingenuity behind it.
A heat shrink chamber combines everything into one compact area and minimises handling. The film is held on a built-in unroller and runs across a loading table which sits between the upper and lower film layers to separate them for easy product insertion and the entire sealing area is enclosed in a chamber with a clear acrylic hood.
You place your product on the table then draw it with the film across to the sealing unit, where it sits on a height-adjustable table so that the film seal is placed halfway up the pack side.
When you lower the L-bar, it locks into position with an electromagnet for the duration of the sealing/shrinking/cooling cycle. The film is sealed and hot air is circulated around the chamber to evenly shrink the film and then the chamber opens for the pack to be removed.
- Sealer and shrink tunnel systems
A separate sealer and shrink tunnel works in a similar way to a chamber shrink wrapper but instead of the chamber surrounding the sealing unit, a belt conveyor carries the pack through a tunnel where hot air circulates to shrink the film.
This takes up more space but is faster than a chamber as one pack can be passing through the shrink tunnel while the next is being sealed, so it’s more popular for high-volume work.
Ripack® gas shrink systems, Pacplus® and Hacona® heat sealers and Pacplus®/Transpal® shrink film products are available through Southgate® and their network of approved distributors throughout the UK and across Europe. For more details call 01553 69 29 69 or email email@example.com.
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