Typical error patterns in blown film extrusion and what you can do about them
In blown film extrusion, all it takes is a small irregularity and a defect will spread over the entire length of the roll – including expensive scrap metres. We have summarised the most common defect patterns so that you can link cause → effect → solution more quickly in production.
This is just a small extract from our web seminar on the topic of defects in blown film extrusion.
Quick overview
| Pattern | Typical causes | First countermeasures |
|---|---|---|
| Gel/fisheye inclusions | Unmelted polymers, additive agglomerates, filter breakage | Finer screen pack, check material quality, more frequent screen changes |
| Streaking | Temperature gradients in the extruder or die, worn channels | Calibrate heating zones, plan nozzle cleaning |
| Thickness variations (gauge variations) | Blurred profile control, line speed too high, fluctuating viscosity | Optimise profile control, adjust train speed, close-meshed data recording |
| Bubble instability (breathing, neck-in) | Melt viscosity too low, incorrectly set cooling air flow | Increase melt temperature/feed rate, symmetrise cooling ring |
| Angel Hair & Dust in the granule path | Excessive delivery pressure, abrasive pipes, lack of dust extraction | Reduce pressure, smooth pipe geometry, retrofit dust extraction system |
| Holes / Pinholes | Impurities, bodies, gel particles, overstretching in the fume cupboard | Material screening, reduce tensile stress, check tensile/removal unit |
| Wrinkles & flatness errors | Misaligned pull-off rollers, uneven cooling | Readjust roller parallelism, homogenise cooling flow |
| Telescoping on the winder | Uneven web tension, layer heat, winding core not centred | Optimise web tension profile, reduce winding temperature, check core alignment |
| Odour problems (especially with recyclates) | Volatile contaminants, excessively long dwell times, additive degradation | Vacuum degassing, check fresh recyclate mixture, antioxidants |
What does this mean for your line?
- Document process data completely – this is the only way to recognise correlations quickly.
- Do not extend maintenance cycles – the sieve, nozzle, dosing unit etc. are the “weak points” of every line.
- Clever use of recyclates – melt filtration, compatibilisers and defined mixing strategies reduce fluctuations.
With this checklist in mind, you can solve the most common faults much faster – and ensure stable quality and fewer rejects. Please contact us for in-depth analyses or customised troubleshooting workshops. InnoTalk remains your sparring partner when it comes to best practice in flexible packaging production.
You can access the entire web seminar here at any time.
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