Types of Twin-Screw Extruders: How To Choose Based on Material, Production Scale, And Efficiency

Twin-screw extruders are widely used processing equipment in industries such as plastics, rubber, and food. Their models and production efficiency vary depending on design differences, size specifications, and application fields.

1. Classification by Screw Rotation Direction

• Co-rotating Twin-Screw Extruder
  Features: Both screws rotate in the same direction, providing strong shearing force and excellent mixing.
  Applications: Suitable for processes requiring high filling, strong shearing, and effective mixing—such as plastic compounding, blending, and reactive extrusion.
  Production Efficiency: High mixing efficiency; ideal for complex formulations, though the output rate is relatively lower.

• Counter-rotating Twin-Screw Extruder
  Features: The screws rotate in opposite directions, offering strong conveying ability but lower shear force.
  Applications: Suitable for processing high-viscosity and heat-sensitive materials.
  Production Efficiency: Higher output rate but slightly weaker mixing capabilities.

2. Classification by Screw Structure

• Parallel Twin-Screw Extruder
  Features: The screws are arranged in parallel, offering a compact structure and easy maintenance.
  Applications: Widely used in plastic compounding, pelletizing, and reactive extrusion.
  Production Efficiency: Suitable for small to medium-scale production with high flexibility.

• Conical Twin-Screw Extruder
  Features: The screw diameter decreases from the feeding end to the discharge end, providing a high compression ratio.
  Applications: Mainly used for PVC processing and profile extrusion.
  Production Efficiency: High output, especially suited for high-viscosity materials.

3. Classification by Screw Engagement Degree

• Fully Intermeshing Type
  Features: The screw threads fully intermesh, providing strong shear and efficient mixing.
  Applications: Ideal for processes requiring high mixing and high filling.
  Production Efficiency: Excellent mixing performance, but lower extrusion capacity.

• Non-Intermeshing Type
  Features: The screws do not intermesh, resulting in lower shear force but stronger conveying capacity.
  Applications: Suitable for processes that require low shear and high throughput.
  Production Efficiency: High output rate, though with reduced mixing effectiveness.

4. Classification by Purpose

• General-Purpose Twin-Screw Extruder
  Features: Suitable for processing a wide range of materials, offering high flexibility.
  Production Efficiency: Moderate, ideal for small-batch and multi-variety production.

• Special-Purpose Twin-Screw Extruder
  Features: Custom-designed for specific materials or processes, such as for PVC or reactive extrusion.
  Production Efficiency: Highly efficient for targeted applications.

5. Classification by Size (Screw Diameter)

• Small (20mm, 35mm, 50mm): Suitable for laboratory or small-scale production with low output.

• Medium (65mm, 75mm, 90mm): Ideal for mid-scale production with moderate output.

• Large (120mm, 135mm, 160mm): Designed for large-scale production with high output.

  
  

Factors Affecting Production Efficiency

• Screw Design: Thread geometry, pitch, and compression ratio directly influence conveying and mixing.

• Rotational Speed: Higher speed improves efficiency but may risk material degradation.

• Heating and Cooling System: Proper temperature control enhances production stability and efficiency.

• Material Properties: Viscosity, flowability, and thermal stability significantly affect extrusion performance.

• Process Parameters: Feeding rate, screw configuration, and die design also impact overall efficiency.

When selecting a twin-screw extruder, it’s essential to comprehensively evaluate material properties, process requirements, and production scale.

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