Plastic film recycling machines face a problem that rigid plastic processors never encounter: soft film won’t feed properly into standard extruders. If you’ve tried running LDPE bags, LLDPE stretch wrap, or agricultural film through a conventional hopper-fed system, you’ve likely experienced erratic output, production stops, and frustrated operators.
The solution isn’t a bigger hopper or a different screw design. Recycling soft plastic requires densification before extrusion, which is why professional film recyclers use integrated verdichter pelletiseermachine systems that solve the feeding challenge at its source.
Why Soft Film Can’t Feed Into Standard Extruders
Standard extruders were designed for rigid plastic flakes, regrind, and pellets—materials with bulk densities between 400-600 kg/m³. Soft plastic film has a bulk density of just 30-50 kg/m³, creating three critical feeding problems.[1]
Hopper Bridging and Flow Interruption
Loose film creates arches or bridges across the hopper throat, blocking material flow. When the bridge collapses, a surge of material floods the screw, followed by starvation when the next bridge forms. This cycle makes consistent melting impossible.
The phenomenon occurs because film’s low weight and high surface friction allow it to support its own weight across open spaces. Rigid flakes, being denser and more granular, flow by gravity without bridging.[2]
Screw Starvation From Low Bulk Density
Even when film enters the feed throat, it doesn’t pack into the screw flights like rigid material does. The screw threads spin through loose material without gripping it, failing to generate the compression needed to push material forward and build pressure.
This causes the extruder to run partially starved. Operators see inconsistent motor amperage, fluctuating melt temperatures, and output rates far below the machine’s rated capacity.
Air Entrapment and Processing Problems
Film wraps around itself, trapping air pockets that carry through to the melt zone. These pockets create foam, porosity in pellets, and oxidative degradation from the heated air. The vacuum degassing system—sized for normal material—can’t handle the volume of entrapped air.
How Cutter Compactor Systems Solve Film Feeding
Een snijder-kompactor pelletisatiemachine addresses these problems by adding a densification stage before the extruder. The system has two main components: a cutter-compactor chamber and a single-screw extruder.
Densification Stage
Film enters a heated chamber containing rotating blades and a compression screw. The blades cut film into smaller pieces while friction and gentle heat (80-120°C) soften the material. Rotating compression screws force the softened film together, expelling air and creating a dense, cohesive mass with bulk density increased to 300-400 kg/m³.
This densified material behaves like rigid flakes. It flows consistently, packs into screw flights, and moves predictably through the system.
Controlled Feeding to Extruder
The compactor force-feeds densified material directly into the extruder feed throat, maintaining constant material supply regardless of what’s happening upstream. This eliminates the bridging and starvation issues that plague hopper-fed systems.
The extruder receives a steady stream of pre-heated, air-free material at consistent bulk density. Operators can control output by adjusting compactor speed, achieving stable production rates hour after hour.
Improved Degassing Performance
Because the compactor expels most entrapped air before extrusion, the vacuum degassing system works within its design parameters. This produces cleaner pellets with fewer defects and allows processing of printed films where volatiles from inks need removal.
Material Applications for Compactor Pelletizers
Compactor systems excel with the materials that challenge conventional extruders:
- LDPE and LLDPE film: Stretch wrap, pallet wrap, produce bags, retail shopping bags
- Agricultural film: Greenhouse covers, silage wrap, mulch film (after washing)
- Industrial film scrap: Edge trim from film extrusion, production rejects, roll ends
- HDPE film: T-shirt bags, food packaging film
- PP woven materials: Raffia bags, cement bags, jumbo bags (FIBCs) after shredding
These materials share common characteristics: low bulk density (under 100 kg/m³), high flexibility, and tendency to nest or tangle. All benefit from compaction before extrusion.
Performance Comparison: Standard vs. Compactor Systems
When processing 200 kg/h of LDPE stretch film, a standard 100mm extruder with hopper feeding struggles to maintain output. Operators report frequent bridging, output fluctuation of ±30%, and frequent stops to clear the hopper.
The same extruder paired with a cutter compactor achieves rated capacity consistently, with output variation under ±5%. The compactor adds 37-45 kW motor power but eliminates the production losses from inconsistent feeding. Most operations see payback within 12-18 months from improved yield and reduced downtime.
Energy consumption increases by approximately 15% with a compactor system, but this is offset by higher throughput and better pellet quality that commands premium pricing.[3]
Key Design Features to Look For
Not all compactor systems deliver the same performance. When evaluating equipment, check these specifications:
Compactor chamber volume: Should provide 3-5 minutes of residence time at rated capacity. Undersized chambers can’t properly densify material; oversized chambers cause excessive material degradation.
Heating control: Independent temperature zones prevent overheating while ensuring adequate softening. Look for 2-3 controllable zones minimum.
Blade configuration: Replaceable cutting blades reduce maintenance costs. Blade design affects power consumption and material size reduction.
Feed interface: Direct coupling between compactor and extruder maintains consistent material transfer. Avoid systems that drop material between components.
Is a Compactor System Right for Your Operation?
Choose a compactor pelletizer if you’re processing primarily soft films and bags. The investment makes sense when film represents over 60% of your feedstock, or when you’re experiencing persistent feeding problems with your current system.
Operations processing mixed material—some rigid, some film—benefit from a compactor system’s versatility. The compactor handles film effectively while processing rigid material normally, giving you flexibility as feedstock composition changes.
Facilities processing exclusively rigid plastic (bottle flakes, container regrind, pipe scrap) rarely need compaction. A standard extruder with proper hopper design serves these applications more economically.
Making Film Recycling Profitable
Film recycling struggles to compete economically because hauling and processing costs often exceed pellet value. Compactor systems improve the economics by increasing throughput, reducing labor for dealing with feeding problems, and producing higher-quality pellets that sell for premium prices.
The Rumtoo ML Series demonstrates this approach, processing 150-1200 kg/h depending on model size, with integrated compaction, degassing, and filtration in a single system. The design addresses the complete challenge of recycling soft plastic, not just extrusion.
Successful film recycling requires matching equipment to material characteristics. When your feedstock is soft, low-density film, a compactor pelletizer transforms a difficult process into a reliable, profitable operation.