Pallet Wrapper Inconsistent Wrap Pattern
An inconsistent wrap pattern is usually a settings or speed ratio issue rather than a mechanical fault. Where the coverage gaps or bunching appear - top, bottom, or specific height bands - tells you which parameter to look at first.
Common symptoms
Note whether the problem appears at a specific height, at the start or end of the cycle, or changes between loads. That narrows it considerably before touching any settings.
Gaps in coverage at consistent height
Gaps that appear at the same height on every load suggest the carriage travel speed or wrap count isn't covering that zone properly. It may be a setting issue, or the carriage isn't travelling at the programmed speed through that range.
Film bunching or layering at the bottom
Film bunching at the base of the load usually means too many wraps are being applied at that height - either a pre-wrap setting is too high, or the carriage is pausing or slowing at the bottom before starting its upward travel.
Top of load under-wrapped compared to middle
If the load profile means the top is narrower than the body, the carriage may be moving through the top section too quickly relative to the number of turntable rotations. A load height sensor that's reading incorrectly can also cut the cycle short.
Wrap count or film width not covering the load
If the film width isn't covering the full load height in a single pass, more passes are needed - but the program may not be configured for that load profile. This is usually a program setting rather than a machine fault.
Pattern changes between loads of the same type
Inconsistency between identical loads points to something variable - a load height sensor reading slightly differently, a speed that's fluctuating, or film tension varying due to a reel that's running down. It's rarely a static setting issue.
Pattern changed after a settings adjustment
If the wrap pattern changed after someone adjusted the program, the settings are the first place to look. Changes to pre-stretch ratio affect effective film width, which changes how much height each pass covers - an indirect effect that's often missed.
Typical causes
Wrap program settings out of range for the load
The wrap program controls carriage speed, wrap count, top and bottom wrap height, and pre-wrap passes. If any of these are set for a different load profile than what's being run, the pattern will be inconsistent. This is the most common root cause and the easiest to check first.
Carriage and turntable speed ratio
The overlap between film passes is determined by the ratio of carriage travel speed to turntable rotation speed. If this ratio has drifted - or was never set correctly for the film width being used - coverage will be uneven. The ratio changes if either drive speed changes.
Load height sensor fault or misalignment
Automatic wrappers use a height sensor to determine where the load ends and tell the carriage when to reverse. If the sensor is misaligned or reading inconsistently, the carriage will stop or reverse at the wrong height on each cycle, producing variable top coverage.
Pre-stretch roller settings affecting effective film width
Pre-stretching film lengthens it but also narrows it. A high pre-stretch ratio means the film is narrower as it leaves the carriage, so each pass covers less height. If pre-stretch has been increased - intentionally or otherwise - the same carriage speed will leave more gaps than before.
What to check first
Take a photo of the wrap pattern on the finished load before changing anything. It's the clearest record of what the machine is actually doing.
Check the active wrap program against the load
Go into the machine program and check the configured load height, wrap count, and carriage speed. Compare them against the actual load being run. If someone has changed the program or switched to a different program number, the settings may simply be wrong for this load type.
Check the load height sensor is reading correctly
On a machine with automatic height sensing, check that the sensor reads the load correctly as it's loaded onto the turntable. If the reading is inconsistent between identical loads, the sensor is the likely cause of the variable pattern. Check for obstruction, misalignment or dirt on the sensor face.
Note any recent changes to pre-stretch settings
Ask whether anyone has adjusted the pre-stretch ratio since the pattern was last acceptable. A higher ratio narrows the film and changes how much height each pass covers. If pre-stretch has changed, try reverting it and see whether the pattern improves before adjusting carriage speed.
Run three consecutive loads and compare the pattern
If the pattern is inconsistent between loads, run three and photograph each one. Consistent problems point to a setting. Variable problems point to a sensor, a speed that's fluctuating, or a reel quality issue. The pattern across multiple loads is more useful than any single example.
If any of these apply, don't wait
- The wrap pattern is inconsistent between identical loads and you can't find the variable
- The load height sensor is showing inconsistent readings or the carriage is reversing at the wrong point
- You've reviewed the program settings and they look correct but the pattern is still wrong
- The pattern changed after a machine service or repair and hasn't recovered
Wrap pattern faults that don't respond to settings checks are often mechanical - carriage speed drift, sensor calibration, or a drive parameter that's changed. These need instrumented testing to diagnose accurately.