Heat shrink films and machines are in our DNA. We've been doing them for more than 25 years. We've seen just about every conceivable package type from perfumes and cosmetics to printed materials to t-shirts to food. We have the experience to help you understand how to shrink wrap a package, pack it and ship it so that it's delivered to your customer looking exactly how you envisioned - perfect.
When considering a shrink wrap machine, the first two things to look at are the size of the package and the number of packages you need to produce in a given amount of time. For instance, an average tabletop system can reliably produce 5 - 7 packages per minute.
A semi-automatic L-bar sealer and tunnel are good for medium production of up to around 15 packages per minute.
If you need to produce more than that, you should consider an automatic system. They will run between 15 and 60 packages per minute.
And finally, if you have ultra-high production goals, you'll need a high speed fully automatic machine that's capable of producing between 60 and upwards of 200 packages per minute.
Numbers are fine but what does 5, 50 or 150 packages per minute look like?
Next, consider what kind of shrink film to use. You can choose between PVC (Reynolon, Syfan) and Polyolefin (Bollore, Sealed Air, Clysar, Syfan) shrink wrap material. Each has its own strengths and weaknesses.
For instance, Reynolon PVC has outstanding optical characteristics. It's very clear and glossy. It shrinks at a lower temperature which makes it ideal for small systems. To use it, you'll need to keep your nichrome wire covered with teflon or teflon tape.
Sealed Air Cryovac, Clysar and Bollore polyolefin shrink films (olefins) have good optics and are generally stronger and resist tearing. They also have higher shrink forces and tend to be easier to seal with no covering of the nichrome wire needed. The drawbacks include higher shrink temperatures and shrink force that can sometimes distort the finished package.
Both PVC and Polyolefin shrink films can be shrunk using a shrink wrapper or a heat gun which can also be used with shrink wrap bags and shrink tubing.
Shrink bundling film is made from polyethylene and is typically used to wrap trays of bottled water, food products and other types of heavy and/or industrial packages.
Wondering what makes shrink wrap shrink? Well, it starts with the plastic polymer. Polymers are very long molecules. In fact the best analogy I can use is that the plastic polymer is like a length of Christmas lights. As we all know, a length of Christmas lights in its natural state is all bunched up and tangled. In fact the more sets of lights you have, the more they are all scrambled.
Plastic polymers, like Christmas lights, are naturally scrambled up and tangled. However, shrink wrap film is manufactured so that the plastic polymers chains are oriented so that they are un-naturally stretched out. These polymer molecules are now are longer by forcing them into this awkward state. During orientation, the polymer is locked, or frozen, into its elongated state. This straightened, longer, and oriented polymer shrink film can now be used to enclose any number of products. The only thing left to do is add the special ingredient to create the magic of shrink.
In the case of shrink film the special ingredient is heat. Heat applied to the shrink film increases the molecular motion of the polymers and causes the elongated polymers to recoil, or shrink back to its natural random and disordered conformation. Excess energy increases molecular motion (wouldn't you move if a fire were placed under your backside?). Different polymers react to this heat shrinkage differently but 50% shrinkage from the initial oriented size is not unusual. As in stretch film the tensile strength of the shrink film also increases when heated. This basic explanation applies to PVC, polyesters and polyolefin type shrink films.
Here is a list of common shrink wrap packaging terms you'll want to get familiar with:
Shrink Films Films which have gone through an orientation step in manufacturing process, which shrink significantly with application of heat.
Singlewound (SW) Film A term used to describe a single layer of film wound around a core. It is generally used on automatic form-fill-seal equipment. Centerfold (CF) Film This is a film that has been folded in half lengthwise and wound around a core. Centerfold Film is usually used on slower, semi-automatic and manual packaging equipment which inserts the product between the folded film and then heat seals the remaining 3 edges. Natural Centerfold (In-Line) An extrusion line used to produce the centerfolded film which slits the tubular film before it is wound to core.
Mechanical Centerfold The process by which single-wound or flat film is mechanically folded for use on L-Bar Sealers.
Core A paper tube on which film is wound. Cores are furnished in 3" and 6" inside diameters; 3" is standard. Cryovac uses 0.660 wall cores that weighs 0.2 lbs. per inch.
Gauge A term used to describe the thickness of film. One mil is equivalent to 1/1000 of an inch. 50- gauge film is 1/2 mil thick, 100-gauge is 1 mil thick. Wind The direction that centerfolded film is wound on a core. Most centerfold film can unwind either from top or bottom of the roll when viewed horizontally from the open side.
Monolayer Film A single layer film extruded from one or a blend of several raw materials (Resins) Multilayer Film A film formed with multiple layers of similar or differing polymers. The purpose is to obtain specific properties and characteristics.
Cross Direction (CD) Film direction in the width of the film.
Machine Direction (MD) Film direction in the length of the film as it comes off the roll or travels through the machine.