Pallet Wrapper Film Breaking
Film breaks are almost always caused by a mismatch between film tension, pre-stretch ratio, and what the load can withstand. Where the film breaks in the cycle - and where on the load - tells you which variable is out.
Common symptoms
Where the film breaks - at the load corners, at a specific height, or at the pre-stretch rollers - points to different causes. Note the location before adjusting anything.
Film breaks consistently at load corners
Corner breaks are the most common film failure. Sharp pallet corners or protruding product create a stress concentration that exceeds the film's stretch limit. Usually a tension or pre-stretch setting issue, but the load profile matters too.
Film breaks at the pre-stretch rollers
A break at the rollers means the film is being stretched beyond its limit before it even reaches the load. Pre-stretch ratio is set too high for the film grade being used, or a roller has developed a damaged surface that's nicking the film.
Film breaks early in the cycle, consistently
Breaks during the first few rotations often happen because the film tail wasn't secured properly to the load before the cycle started, or because the initial ramp-up speed is too fast for the film grade.
Film breaks at the same height on every load
A consistent break height usually means something at that level on the load - an exposed corner, a protruding item or an unstable layer - is snagging the film at the same point each cycle.
Film breaks started with a new reel
Different film grades and suppliers have different stretch characteristics. A reel that looks identical to the previous one may have a lower elongation rating, which means it can't handle the same pre-stretch ratio.
Film tears rather than breaks cleanly
A tear that propagates along the film width suggests a nick or damage on a pre-stretch roller surface. One small surface defect can initiate a tear on every wrap at that roller contact point.
Typical causes
Pre-stretch ratio too high for the film grade
Every stretch film has a maximum elongation limit. If the pre-stretch rollers are set to stretch the film beyond that limit - or close to it - corners and load variations will push it over the edge. A ratio that works for one film grade may be too aggressive for another.
Film tension set too high
Wrap force is set to provide load containment, but too much tension leaves the film running close to its break point across the full cycle. Any irregularity in the load - a corner, a protruding edge - then pushes it over.
Film quality or reel condition
A crushed core, a poorly wound reel or a film grade that's degraded through storage will break at tensions that would be fine for good stock. A splice within the reel will almost always break under pre-stretch conditions.
Load profile or sharp corners
The load itself is part of the equation. Unprotected sharp pallet corners, protruding product or an unstable load that shifts during wrapping all create stress concentrations that the film can't bridge without breaking.
What to check first
Note where in the cycle and where on the load the film breaks. That combination narrows it down quickly.
Try a different reel of known-good film
Before adjusting any settings, try a reel you know has worked recently. If the breaks stop, the film is the problem - the current reel is damaged, degraded or a different grade. This test costs nothing and clears one of the most common causes.
Reduce tension or pre-stretch and test
Drop the wrap force or pre-stretch ratio by a small increment and run a test cycle. If the breaks stop, the settings were too aggressive for the current film or load. Adjust back up gradually until you find the limit, then back off from there.
Check the pre-stretch rollers for damage
With the machine isolated, visually inspect the pre-stretch roller surfaces. Look for nicks, grooves, built-up film residue or any rough patches. Even a small defect on the roller surface will initiate a tear in the film on every revolution.
Look at the load itself
Check the pallet corners - exposed wood splinters, metal banding or protruding product edges all catch film. If breaks are happening at corners consistently, corner boards on the pallet are often the fastest practical fix while the settings are reviewed.
If any of these apply, don't wait
- Film breaks persist after reducing tension and pre-stretch and trying a fresh reel
- Pre-stretch rollers show visible damage, scoring or built-up film that won't clear
- The break location has changed since the machine was last serviced
- Film consumption has increased significantly and you can't identify why
A pre-stretch roller that's damaging film will keep causing breaks regardless of settings. If the mechanical components are the cause, no amount of tension adjustment will fix it.