The extruder screw is the most important component inside a plastic extrusion machine. It determines melt quality, output capacity, mixing performance, and energy consumption.
Understanding the key parts of an extruder screw helps manufacturers choose the right design for HDPE, LDPE, PP, PET, PVC, WPC, and high CaCO₃ filler extrusion.
In this guide, Zhoushan Juyuan Plastic Machinery Co., Ltd. explains each screw part and how it affects the plasticizing process.
If you want to learn more about barrels, check our related article:
👉 Extruder Barrel Guide (Internal link)
1. Screw Root (Core Shaft)
The screw root is the central shaft of the extruder screw.
Functions
- Supports the screw flights
- Transmits torque from the gearbox
- Determines the screw strength and stiffness
For high-speed screws (200–250 RPM), the root must be made of high-strength alloy steel (SKD61, 38CrMoAlA, GH4169).
2. Screw Flights (Threads)
The flights are the helical protrusions along the screw.
Functions
- Convey plastic material forward
- Create pressure and shear
- Control melting and mixing
The geometry of the flights (pitch, depth, width) determines material behavior in each zone.
3. Feed Zone
The first section of the screw.
Purpose
- Receives raw material from the hopper
- Starts conveying
- No major melting occurs here
A deeper channel design ensures efficient feeding.
4. Compression Zone (Transition Zone)
Material starts melting in this section.
Functions
- Gradually reduces channel depth
- Increases pressure and shear
- Starts melting pellets into a molten mass
The compression ratio must match the material (e.g., HDPE requires a different ratio than PVC).
5. Metering Zone
The final section before the die.
Purpose
- Completes melting
- Homogenizes the melt
- Builds stable pressure for extrusion
A stable metering zone improves output consistency and product quality.
6. Barrier Section (Optional)
Common in modern high-output screws.
Benefits
- Separates solid material from melt
- Improves melting efficiency
- Increases throughput
- Reduces melt temperature variations
This design is ideal for HDPE/LDPE pipe, film, and pelletizing lines.
7. Mixing Section
Different types exist, including:
- Maddock mixing head
- Spiral mixing section
- Pin mixing structure
- Dynamically balanced high-speed mixer section
Functions
- Enhance color dispersion
- Improve filler distribution (CaCO₃ 40–80%)
- Stabilize melt temperature
High-mixing screws are essential for recycled materials and high-filler applications.
8. Screw Tip / Head
Located at the screw end, connecting the screw to the die.
Functions
- Builds final pressure
- Controls backflow
- Ensures uniform melt delivery
9. Check Ring (Non-return Valve)
Common in injection molding screws but also seen in extrusion under special designs.
Purpose
- Prevents melt backflow
- Stabilizes pressure
- Ensures consistent melt feeding
10. Drive End
This is the rear connection part between the screw and the gearbox.
Features
- Keyways or splines
- Precision alignment
- High fatigue strength
High-speed screws require perfect dynamic balance.
Materials Used for Screw Parts
Screw life and performance depend heavily on the material.
Common Materials
- 38CrMoAlA (Nitrided steel)
- SKD61 / H13
- DC53 tool steel
- GH4169 (Inconel alloy)
- Carbide alloy overlays (for extreme wear resistance)
For high CaCO₃ (40–80%) and recycled plastic, bimetallic wear layers are strongly recommended.
Related Internal Link
👉 How an Extruder Screw & Barrel Works (Internal link)
👉 Complete Guide to Extruder Screw Barrels (Internal link)
Why Choose Juyuan Extruder Screws?
✓ High-speed screws for 200–250 RPM
✓ Wear-resistant bimetallic technology
✓ Custom designs for HDPE / LDPE / PP / PVC / PET / ABS
✓ Strict CNC machining and dynamic balancing
✓ Compatible with global brands: Cincinnati, KraussMaffei, Coperion, JSW, Bausano, Bandera, AMUT
We support custom-made screw parts according to drawing or sample.
📞 Contact Us
Zhoushan Juyuan Plastic Machinery Co., Ltd.
🌐 Website: https://juyuan-machinery.com/
📧 Email: cxj.job@gmail.com
📱 WhatsApp / WeChat / Phone: +86 13905808474