Twin-screw extruders are widely used, especially in PVC profile and pipe production. There are two basic screw arrangement types in these systems: parallel twin screw and conical twin screw. Both have their own distinct advantages and application areas.
What Is a Parallel Twin Screw?
In parallel twin screws, the two screws are positioned at the same diameter along their length and parallel to each other. The center distance between the screws is constant along the length. This structure offers high production capacity and a more compact gearbox design.
What Is a Conical Twin Screw?
In conical twin screws, the screws taper from the feed opening toward the screw tip. This geometry allows for larger-diameter bearings, enabling higher torque transmission and therefore higher pressure resistance.
Capacity and Efficiency Comparison
Parallel twin screws generally have higher specific capacity (kg/hour/rpm) than conical systems for the same diameter and are advantageous in terms of energy efficiency. Conical systems, since they allow the use of larger-diameter bearings and gears, are preferred for demanding PVC formulations requiring higher torque and pressure.
Maintenance and Ease of Replacement
In conical twin-screw systems, screw and barrel disassembly/reassembly can be more practical in some machine designs thanks to the conical geometry. In parallel systems, dimensional consistency in screw and barrel manufacturing can be controlled more simply.
Which Is Preferred for Which Application?
- High-capacity, standard PVC profile lines: parallel twin screw is the common choice
- Demanding formulations requiring high torque and pressure (rigid PVC, highly filled formulations): conical twin screw
- Priority on a compact machine design: parallel twin screw
You can contact our technical team for screw-barrel manufacturing in original dimensions matching your existing machine's screw type.
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