Haichen durable high quality injection molding machine screw barrel spare parts
The screw barrel's design integrates material science, structural engineering, and process control. Innovations in wear resistance, intelligent monitoring, and modularity are driving efficiency and precision in modern injection molding.
| Injection molding machine screw barrel |
The screw barrel of the injection molding machine is the core component of the injection molding equipment, and its functions cover plasticizing, conveying, mixing and injection of plastics. |
1. Structural and Functional Design
- Segmented Screw Design
The screw is typically divided into three zones:
- Feed Zone: Fixed channel depth (H1≈0.12−0.16DH1≈0.12−0.16D) for conveying solid pellets and preheating. A shorter feed zone may cause premature melting, leading to instability.
- Compression Zone: Gradually decreasing channel depth to achieve full melting via shear and pressure.
- Crystalline plastics (e.g., nylon) require a short, abrupt compression zone.
- Amorphous plastics (e.g., ABS) need a long, gradual compression zone.
- Metering Zone: Shallowest channel depth (H3H3) to ensure melt uniformity. Excessively small H3H3 risks degradation from shear heat, while overly large H3H3 increases backflow.
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Specialized Structural Enhancements
- Magnetic Isolation: Homopolar magnetic fields at the screw tip and check ring interface prevent metal-to-metal friction, eliminating particulate contamination.
- Mixing Elements: Pins or barrier segments enhance melt homogenization through repeated splitting and recombination.
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Compression Ratio and Geometry
- Compression ratio (ε=H1/H3ε=H1/H3, typically 2-3). Higher εε improves shear but reduces throughput.
- Pitch (S≈DS≈D) and flight width (e=0.08−0.12De=0.08−0.12D) balance conveying efficiency and leakage.
2. Material and Manufacturing
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Barrel Materials
- Standard: Nitrided steel (HV 850-950, nitrided layer 0.5-0.7 mm).
- Bimetallic: Tungsten carbide-lined barrels (>>2 mm, HRC 55-62) extend service life 4-5×.
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Screw Materials
- Base: Plasma-nitrided 38CrMoAl steel.
- Surface Treatments:
- Chrome plating (HRC≥55HRC≥55, 0.05-0.1 mm) for corrosive plastics (e.g., PVC).
- Bimetallic coatings (Ni-based + 80% WC) for extreme abrasion resistance.
3. Process Control and Maintenance
- Temperature Management
- Zonal heating (feed → compression → metering) must align with polymer melt behavior. For example:
- Polycarbonate (PC) requires higher temperatures.
- Nylon demands rapid heating.
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Wear Mitigation
- Speed Control: Reduce RPM (<100 rpm) for glass-filled plastics to minimize fiber-induced wear.
- Material Drying: Moisture-free plastics prevent steam erosion in high-pressure zones.
- Concentricity: Maintain screw-barrel clearance (0.002-0.005D) to avoid backflow and efficiency loss.
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Maintenance Protocols
- Install magnetic filters to capture metal contaminants.
- Regularly inspect nitrided/chromed layers; refurbish or replace if worn beyond limits.
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