Plastic recycling extruder machines fall into two main categories: single screw and twin screw systems. Each design serves distinct purposes in plastic processing, and choosing the wrong type can cost you thousands in unnecessary equipment investment and operating expenses.
Most recyclers processing post-consumer film, bags, or rigid plastic waste need straightforward melting and pelletizing. If that describes your operation, a single screw extruder likely offers the best value. Twin screw systems excel at specialized compounding tasks that most recycling facilities never perform.
How Single Screw Extruders Work
A single screw extruder uses one rotating screw inside a heated barrel to move, melt, and pressurize plastic material. The screw has three zones: feed, compression, and metering. Material enters the feed zone as flakes or regrind, gets compressed and melted in the middle section, then exits through a die as molten plastic strands that are cut into pellets.[1]
This design has dominated plastic processing for decades because it reliably handles high volumes of single-polymer materials. PE film recyclers and PP rigid plastic processors depend on single screw systems for their simplicity and durability.
How Twin Screw Extruders Work
A twin screw extruder uses two intermeshing screws rotating inside a barrel. In co-rotating designs (the most common type), both screws turn in the same direction, creating intense mixing action as material passes through.[2]
The modular screw design allows processors to customize mixing intensity, add multiple feeding points, and incorporate degassing zones. This flexibility makes twin screw machines ideal for compounding operations that blend different polymers, disperse additives, or incorporate fillers into a base resin.
Key Differences: Single Screw vs. Twin Screw
Mixing Capability
Single screw extruders provide moderate mixing through screw geometry and barrel temperature control. This suffices for melting uniform recycled material like sorted PE film or clean PP regrind.
Twin screw extruders deliver intensive distributive and dispersive mixing. The intermeshing screws force material through narrow gaps, breaking up agglomerates and distributing additives at the molecular level. This capability matters when producing masterbatch or compounding filled materials, but most recycling operations never need this degree of mixing intensity.
Material Versatility
Single screw systems work best with clean, sorted plastics of a single polymer type. They can handle some contamination—dust, labels, minor moisture—but expect consistent input material.
Twin screw extruders process heavily contaminated mixed plastics and can incorporate additives during extrusion. The self-wiping screw design prevents material buildup even with sticky or degraded feedstock. However, recyclers who properly sort and wash their material rarely need this capability.
Operating Costs
Single screw extruders consume less energy per kilogram of output. A typical PE film recycling line uses 0.3-0.4 kWh/kg.[3] Maintenance requirements are minimal: periodic screw inspection and screen changer filter replacement.
Twin screw systems require 15-25% more energy due to intensive mixing action and higher motor loads. The modular screw segments need periodic inspection and replacement, adding to maintenance costs. Spare parts inventory costs more because screw elements come in dozens of configurations.
Capital Investment
Here's where the difference becomes clear. A single screw pelletizing line processing 300-500 kg/h costs roughly 40-50% less than an equivalent-capacity twin screw system. For a startup recycling operation or a business focused on simple pelletizing, this price difference is significant.
Twin screw extruders justify their higher cost only when you need specialized compounding capabilities: creating color masterbatch, dispersing flame retardants, or processing engineering resins with glass fiber reinforcement.
When to Choose Single Screw
Select a single screw extruder when you're recycling:
- PE or PP film and bags from agriculture, retail, or industrial sources
- Clean post-industrial scrap of a single polymer type
- Washed and sorted rigid plastic regrind (HDPE bottles, PP containers)
- Material that's already been sorted and cleaned to reasonable purity
The single screw design matches the needs of 80% of plastic recycling operations. It's reliable, economical, and produces consistent pellet quality when fed appropriate material.
When to Choose Twin Screw
Consider a twin screw extruder if your business requires:
- Mixing different polymer types (PE/PP blends, ABS/PC alloys)
- Dispersing additives like flame retardants, UV stabilizers, or impact modifiers
- Processing heavily contaminated mixed plastics
- Producing filled compounds with high loadings of glass fiber, minerals, or wood flour
- Manufacturing masterbatch or specialty compounds
These applications represent niche segments within plastic recycling. Most operations focused on converting post-consumer waste into saleable pellets don't need twin screw capabilities.
Which is Best for Plastic Recycling?
For the majority of recycling operations—those processing sorted PE film, PP bags, or washed rigid plastic waste—a single screw extruder delivers the best return on investment. You get proven reliability, lower operating costs, simpler maintenance, and faster payback on your equipment investment.
The Rumtoo ML Series single screw pelletizing line, for example, processes 150-1200 kg/h of soft plastic film with up to 5% moisture content, handling the real-world conditions that recyclers face daily. This performance comes at a fraction of the cost of twin screw systems designed for specialized compounding work you likely don't need.
Reserve twin screw extruders for operations that truly require intensive mixing or that plan to enter the compounding business. Otherwise, you're paying for capabilities you won't use.
Choose your extruder based on what you're actually processing, not on theoretical versatility. Most recyclers find that a well-configured single screw system handles their entire product range efficiently and profitably.