Troubleshooting / Blown film line

Blown Film Line Troubleshooting

The most common blown film line problems on the plant floor, with the likely causes and the fix for each. Part of the OEE Lab troubleshooting directory.

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Problems on this page:

Bubble unstableThickness varies around the filmGels and black specksWrinkles at the nip or winderFilm blocking on the rollDie lines in the filmBubble breaksLow surface treatment levelWinder roll quality poor

Bubble unstable

Hits OEE: Quality

Symptoms: The bubble moves, breathes or wobbles, and the width and thickness change.

Uneven cooling from the air ring
Clean the air ring and check the blower and the air flow around it.
Melt temperature too high
Lower the melt temperature step by step.
Drafts around the bubble
Shield the line from doors and fans.
Output higher than the cooling can handle
Match the output to the cooling capacity.

Prevention: Bubble stability checked after every change of output.

Thickness varies around the film

Hits OEE: Quality

Symptoms: Gauge profile shows thick and thin lanes.

Die gap uneven
Centre the die gap.
Air ring lips dirty or damaged
Clean the air ring lips.
Die temperature zones uneven
Check the die heaters.
Automatic profile control off
Check the profile control system.

Prevention: Gauge profile recorded at each roll.

Gels and black specks

Hits OEE: Quality

Symptoms: Small lumps or dark spots appear in the film.

Unmelted material
Check the barrel temperatures and the screw.
Contamination in the material
Check the raw material and the regrind.
Degraded material in dead spots
Purge and clean the die and adapter.
Screen pack damaged
Change the screens.

Prevention: Gel count checked on samples each shift.

Wrinkles at the nip or winder

Hits OEE: Quality

Symptoms: Creases form as the bubble is flattened or wound.

Collapsing frame out of alignment
Align the collapsing frame.
Nip rolls not parallel
Check the nip roll alignment.
Thickness variation
Fix the gauge profile.
Winder tension wrong
Set the tension.

Prevention: Collapsing frame and nip alignment checked at PM.

Film blocking on the roll

Hits OEE: Quality

Symptoms: Layers stick together and the film is hard to open.

Film not cool enough at winding
Increase cooling or reduce the speed.
Anti-block additive too low
Check the masterbatch dosing.
Winding tension too high
Reduce the tension.
Hot storage
Store rolls in a cool area.

Prevention: Blocking test on new film recipes.

Die lines in the film

Hits OEE: Quality

Symptoms: Lines run along the film in the machine direction.

Damage on the die lips
Inspect and polish the die lips.
Build-up at the die exit
Clean the die exit.
Contamination stuck in the die
Clean the die.
Material degrading
Check the temperatures.

Prevention: Die lips cleaned at each planned stop.

Bubble breaks

Hits OEE: Availability

Symptoms: The bubble tears and the line has to be restarted.

Gels or contamination
Fix the cause of gels.
Film too thin for the blow-up ratio
Check the recipe.
Melt fracture
Check the melt temperature and die gap.
Sudden output changes
Ramp output changes slowly.

Prevention: Breaks logged by cause.

Low surface treatment level

Hits OEE: Quality

Symptoms: Inks or adhesives do not stick to the film.

Corona treater power low
Check the treater output and electrodes.
Electrodes dirty or worn
Clean or replace the electrodes.
Slip additive migrating to the surface
Check the additive levels.
Film stored too long before printing
Use film within its treatment life.

Prevention: Treatment level tested on each roll.

Winder roll quality poor

Hits OEE: Quality

Symptoms: Rolls are telescoped, soft, too hard, or have wavy edges, and customers report unwind problems.

Winding tension or taper not set for the film
Set the tension and taper profile for the thickness and material.
Thickness variation building up in one lane
Use oscillation of the die or the haul-off so thick lanes spread across the roll.
Lay-on roll pressure wrong
Adjust the lay-on pressure to avoid trapping air or crushing the film.
Cores damaged or out of round
Use cores that meet the specification.

Prevention: Roll hardness and edge quality checked at each roll change.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Related equipment guides: extruder · slitter rewinder · flexo press · granulator · vacuum loader · laminator

Stop the same fault coming back

Recurring blown film line stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

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Related tools: full troubleshooting directory · OEE calculator · downtime cost · MTBF / MTTR · glossary

Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover