Nothing slows a packing line quite like a seal that won’t hold. One minute the packs are coming off the machine neatly and the next the film is pulling apart, the cut isn’t clean and someone is re-wrapping by hand while everything behind them waits. When you’re dealing with a shrink wrap machine not sealing, the cause is often more ordinary than it looks, such as a worn part or a setting that’s drifted, though a few faults do need a trained engineer. Knowing which is which can save you hours of downtime, so it helps to start with what a failed seal looks like.
What Does a Failed Seal Look Like?
Before you can fix a seal, it helps to know what kind of failure you’re looking at. The same fault can show up in different ways and different faults can look alike, so think of this list as a way to name the problem rather than diagnose it. These are the symptoms we hear about most often:
- A weak seal that pulls apart when you handle the pack
- A seal that looks fine but splits once it cools
- Film that the L sealer hasn’t cut through
- An incomplete cut-off that leaves the film joined
- Smoking or burnt film around the seal
It’s common to see two or more of these together, because one worn part can cause several. Jot down exactly what you’re seeing and when it started, as that’s often the quickest route to the cause.
What Are the Most Common Causes of a Shrink Wrap Machine Not Sealing?
On many L sealers, seal problems trace back to a few parts that have the most wear. These are the usual suspects, although one of our engineers should always confirm the fault on your own machine:
- Worn or dirty sealing wire or seal bar
These do the sealing, so wear or built-up residue can leave a patchy seal or a cut that doesn’t go all the way through. If your sealing wire keeps breaking, that’s a sign to call an engineer, as wires and bars run hot in use. - Worn PTFE tape
It covers the sealing surface so the film doesn’t stick and once it’s worn or damaged the film can cling and the seals turn out uneven. - A worn silicone pad
It gives the sealing wire a firm, even surface to press against, so a tired pad can leave seals weak or incomplete. - Faults in electrical parts
Thermostats, relays and heating elements control how the sealing area heats, so a fault in one of them is a job for a trained engineer.
Which of these applies depends on the make and age of your machine, so a quick look from an engineer can save a lot of guesswork. Settings and film are the other big culprits and they’re easier to check yourself, so they’re next.
Could Your Settings or Film Be Causing the Problem?
Sealing is a balancing act between the machine’s settings and the film it’s running. If the problem appeared just after you switched film or started wrapping a different size of product, start there, because settings that worked last month may need a fresh look.
It’s tempting to ask what the right seal bar temperature is, but there’s no single answer, as it depends on your machine and your film. Your operator manual is the place to look, or an engineer can advise. The film itself matters too. The wrong type for the job can weaken a seal, as can poor storage or too much tension on the roll. Checking that the film is the right type and running freely costs nothing, so it’s an easy one to rule out first.
What About Faults in the Shrink Tunnel?
Sometimes what looks like a sealing fault isn’t one at all. Film that won’t shrink or burns, stringy film known as angel hair and packs that balloon are all tunnel or film issues, although at first glance they can pass for seal failures.
As a general guide, film that won’t shrink or burns usually comes down to the tunnel’s heat and how long the pack spends inside it. Angel hair and ballooning tend to point to airflow and how well the film vents, with conveyor speed playing a part. The right fix varies from machine to machine, so these faults are best raised with an engineer rather than tweaked by trial and error.
Which Faults Can You Check Yourself and When Should You Call an Engineer?
Not every fault needs a call-out. Your operator manual will normally allow a few simple checks, so look around the seal area for visible wear or dirt and check how the film is threaded and tensioned. It’s also worth confirming that nobody has changed the settings. Let wires and bars cool before you get close, as they run hot and can burn.
The line to hold is a simple one. If a fix involves heating elements, wiring, relays, thermostats or controls, it’s a job for a trained engineer, with the machine isolated first. That’s the short answer to whether it’s safe to repair a shrink wrap machine yourself. In Great Britain, employers also have to keep work equipment maintained and safe under the Provision and Use of Work Equipment Regulations, so an unsafe fault shouldn’t stay in use while you work out what’s wrong.
When it’s time to hand it over, our engineers can take it from there, from minor adjustments to major overhauls, through our shrink wrap machine repair service. That includes electrical repairs for wiring and control issues, mechanical repairs to rollers, conveyors, sealing systems and drive components and urgent callouts and emergency repairs. We look after machines made by Uwrap and other brands, so it doesn’t matter who built yours.
How Often Should a Shrink Wrap Machine Be Serviced?
A seal rarely fails overnight. Wear builds up gradually, which is why regular shrink wrapping machine servicing is the best way to catch problems before they stop production. We recommend a service at least every 12 months and about every six months in high-volume production. That’s our own recommendation rather than a legal requirement.
A full service means inspecting the mechanical and electrical components, then cleaning the key working parts and treating them so they keep moving smoothly. It also gives an engineer the chance to spot a sealing wire or PTFE tape that’s wearing before it fails, which is the heart of good shrink wrap machine maintenance.
Should You Repair, Revamp or Buy a New Machine?
If a machine keeps letting you down, it’s fair to wonder whether it’s worth repairing a shrink wrap machine at all. The answer depends on its age and how often it fails, set against what a repair would cost compared with replacing it. Parts matter too and we hold spares for machines made in the UK, Europe and Asia.
Between those two options sits a third. A revamp replaces worn components and old mechanical systems and it can add software integrations or move a machine from manual to fully automatic. In many cases we find it beats buying new and we’ll help you judge whether it’s financially feasible for your site.
If a machine has reached the end of the road, our used shrink wrapping machines are a sensible fallback. A well-chosen machine can be a long term investment, so it pays to think about the next few years rather than just the next repair.
How Can You Keep Packing While Your Machine Is Being Repaired?
Downtime is usually the costliest part of any fault and orders still need to go out while a repair is under way. Our shrink wrap machine hire service lets you bring in a temporary shrink wrap machine to bridge the gap while your own is repaired. Hire starts from £10/day, with flexible hire periods.
Every hired machine is tested and inspected before it leaves us and we handle delivery and setup. You can choose from L sealers, heavy duty L sealers, chamber machines, sleeve sealers and pallet shrink wrapping machines and our repair and service team is on hand with support if you need help.
Why Choose Uwrap?
We’ve spent over 30 years in the shrink wrap industry, building British machines here in the UK and looking after a wide range of other equipment too. Our engineers service all types of shrink wrapping equipment, whether Uwrap or another brand made it, so when your machine goes down you’re dealing with people who’ve seen most faults before and can tell a quick fix from one that needs a closer look.
That experience covers the whole life of a machine. Because we handle everything from servicing and repairs to revamps and hire, you can stay with one team as your needs change rather than being passed between suppliers. The sectors we support are just as varied, from food and drink to paper and print, so we’re used to the different demands each type of line puts on a machine.
When a shrink wrap machine stops sealing, the cause usually comes down to wear or the balance between the machine’s settings and the film. A few safe checks on the film and settings will rule out the simple causes, while anything involving heat or electrics belongs with a trained engineer, with the machine isolated first. Regular servicing is the best way to stop faults building up and if a repair isn’t the answer, a revamp, a replacement or a hired machine can keep your line moving.
If your shrink wrap machine isn’t sealing, get in touch with our team and we’ll talk through the best next step for your line, from getting the fault diagnosed to keeping you packing in the meantime.
