Key Takeaways
A shrink wrap machine works in two stages. First it seals a loose bag of shrink film around the product using heated sealing jaws. Then it applies controlled heat, usually in a shrink tunnel, so the film contracts and pulls tight against the product. The result is a smooth, tamper-evident, protective wrap. Every shrink wrap machine, from a hand-operated L-bar sealer to a fully automatic sleeve sealer and tunnel, follows this same seal-then-shrink sequence; what changes is how the sealing is done, how the heat is applied and how much of the process is automated. Understanding how shrink wrap machines work comes down to those two stages, so this article explains each one, the sealer types and heat sources, the films they use and what you need to get started. To compare the machines themselves, see our shrink wrap machine range.
L-bar sealer, side bar sealer, sleeve sealer and shrink tunnel: compare them and see them running.
Shrink wrapping a product means sealing it inside shrink film and then heating that film so it shrinks tight. In practice the process has four steps, and the same four steps apply whether the machine is manual, semi-automatic or fully automatic.
The sealing stage of a shrink wrap machine joins the edges of the film around the product before any heat shrinking happens. Different sealer designs suit different product shapes and production speeds. The table below summarises the sealer types you will come across.
| Sealer type | How it seals | Best suited to | Typical volume |
|---|---|---|---|
| L-bar sealer | An L-shaped bar seals two sides of centre-folded film in one stroke and cuts the pack free | Boxes, retail products, books, cosmetics, food trays, small multipacks | Low to medium |
| I-bar (impulse) sealer | A single straight bar seals one edge at a time; the operator turns the product to seal the second edge | Very low volumes, start-ups, occasional wrapping | Low |
| Side bar sealer | A continuous longitudinal seal plus a cross seal, so product length is not limited by the jaw size | Long or irregular items (pipes, frames, printed matter), higher-speed lines | Medium to high |
| Sleeve sealer | Wraps a band of film around a group of products, leaving the ends open, then seals the band | Bottle and can multipacks, cartons, bundling | High |
| Continuous-motion sealer | Fully automatic infeed, sealing and cutting without stopping the product flow | High-speed automated packaging lines | Very high |
Seal quality depends on three settings: jaw temperature, dwell time (how long the jaws stay closed) and jaw pressure. Too little of any of them gives a weak seal that opens in the tunnel; too much burns through the film.
After sealing, the film is heated to its shrink temperature so it contracts around the product. There are three ways to apply that heat, and the right one depends mainly on how many packs you produce per hour.
A shrink tunnel is a heated chamber with a conveyor running through it. Fans circulate hot air around the pack as it passes, so the film shrinks evenly on all sides. Tunnel temperature and conveyor speed are set for the film type and product size; a typical polyolefin film shrinks in the region of 120–160 °C with a few seconds’ dwell. Tunnels give the most consistent finish and are the standard choice for medium and high volumes, paired with an L-bar, side bar or sleeve sealer.
A heat gun is a handheld hot-air blower. The operator moves it over the sealed pack until the film has shrunk. It is inexpensive and suits very low volumes, oversized items or occasional use, but the finish depends on the operator and it is slow.
A shrink chamber (or hood-type machine) combines sealing and shrinking in one enclosure: the lid closes, seals the film and shrinks it in the same cycle. Chambers are compact and simple to run, which suits small businesses, but throughput is limited to one pack per cycle.
Shrink wrap machines run on heat-shrinkable plastic film supplied as centre-folded rolls (for L-bar and side sealers), flat film (for sleeve sealers) or tubing. Three film materials cover most applications.
Film gauge (thickness) is chosen by product weight and handling: lighter retail items use thin POF; heavy multipacks use thick PE. The machine’s sealing jaws and tunnel temperature must be set for the film you choose.
A basic shrink wrapping set-up needs four things, whatever the scale of the business.
Beyond that, a film roll dispenser, a scrap-film winder and a conveyor between sealer and tunnel turn a manual station into a semi-automatic line.
Shrink wrap machines are grouped by how much of the seal-then-shrink process the operator does by hand.
Stepping up a level mainly buys speed and consistency; the physics of sealing and shrinking is the same at every level.
Because shrink wrap machines combine heated jaws, a hot tunnel and moving film, a few features protect operators and keep the output consistent. Look for an emergency stop within reach of the operator, guarding around the sealing jaws and tunnel entry, over-temperature protection on the tunnel, and a film-end or film-tear detector that stops the machine rather than letting it run empty.
Routine maintenance is light: keep the sealing bar and its PTFE cover clean, check film alignment and tension, keep the tunnel conveyor free of film scraps, and confirm heating elements and fans are working. Our shrink wrap machine maintenance guide covers the schedule, and the troubleshooting guide covers weak seals, wrinkles, burn-through and film tearing.
A shrink wrap machine seals film around a product, then shrinks it with heat; the sealer type sets what shapes and speeds you can handle, and the heat source sets the finish and throughput. Once you know your product size, pack count and daily volume, the choice narrows quickly.
Place the product inside the shrink film, close the sealing bar so the heated jaws seal and cut the film around it, then pass the sealed pack through the shrink tunnel, or heat it with a heat gun, until the film shrinks tight. Let the pack cool for a few seconds and check the seals. On a semi-automatic machine the operator only loads the product; the machine seals, cuts and conveys the pack through the tunnel.
It depends on the film and the product. A typical polyolefin film shrinks in the region of 120 to 160 °C with a few seconds in the tunnel, and the tunnel temperature and conveyor speed are set together: too cool and the film stays loose, too hot and it burns through. The tunnel’s temperature controller holds the setting once it is right. Chilled products run at a lower setting.
A heat gun is enough for very small runs, one-off items or products too large for a tunnel, but the finish depends on the operator and it is slow. For regular production a shrink tunnel gives an even, repeatable finish and keeps up with the sealer, which is why many L-bar sealers are supplied with a matching tunnel. Weak seals, wrinkles and burn-through are covered in the troubleshooting guide.
Send us your product size, pack count and daily volume, and we will specify the shrink wrap machine that suits it, with installation by our own technicians, a one-year warranty, CE marking on request and spares held in Johannesburg. You can also book a demo at our Johannesburg showroom and see the machines running.
