Executive Summary

The 55/110 conical twin-screw barrel is precision-engineered for high-output, energy-efficient extrusion of rigid PVC, UPVC, CPVC, and wood-plastic composites (WPC). It utilizes two intermeshing, counter-rotating screws tapering from a 110 mm feed-end diameter down to a 55 mm discharge-end diameter, establishing a natural, progressive compression profile along the barrel bore.

Manufactured from high-grade nitriding alloy steel (such as 38CrMoAlA / SACM645) or premium bimetallic alloys, both screws and barrel undergo rigorous heat treatment. Standard treatments include gas and ion nitriding (case depth: 0.5–0.8 mm at 950–1020 HV) alongside wear-resistant bimetallic PTA welding or hard chrome plating.

This conical geometry delivers exceptional melt pressure, uniform plasticization, and superior shear control at low-to-moderate screw RPM. This configuration enables higher throughput (typically 120–200 kg/h depending on formulation) while strictly preserving thermal stability in heat-sensitive compounds.

Key operational benefits include extended wear life on highly filled PVC blends (CaCO₃/TiO₂), low energy consumption, and uniform self-wiping action that prevents material stagnation and thermal degradation.

Design & Materials

The 55/110 barrel system consists of two counter-rotating, intermeshing conical screws housed within a matched dual-bore cylinder. The taper from 110 mm at the feed section to 55 mm at the metering section generates uniform pressure progression and steady compaction.

• Base Construction: Built using high-integrity 38CrMoAlA (JIS SACM645 / DIN 1.8509) or 42CrMo structural alloy steel, providing core toughness, high tensile strength, and impact fatigue resistance under heavy torque loads.
• Heat Treatment & Nitriding: After precision rough machining and stress relief, components are quenched, tempered, and subjected to deep gas or ion nitriding for over 72–120 hours. This creates a hardened diffusion layer (0.5–0.8 mm depth) with a surface hardness of 950–1050 HV (~58–62 HRC).
• Bimetallic & Specialized Coatings: For processing abrasive compounds (high calcium carbonate loadings) or corrosive polymers (CPVC/fluoropolymers), an inner bimetallic alloy lining (2.0–3.5 mm thick, 58–65 HRC) using tungsten carbide, nickel-base, or cobalt-base alloys is cast into the barrel bore and welded onto the screw flights.
• Precision Machining & Tolerances: Machined on multi-axis CNC screw milling centers with tight straightness tolerances (≤0.015 mm/m) and ultra-smooth surface roughness (Ra ≤0.4 µm on flights; Ra ≤0.2 µm in barrel bores).

Technical Advantages

• High Throughput & Uniform Homogenization: The conical reduction (110 mm → 55 mm) maximizes intake capacity at the feed zone while efficiently building high extrusion pressure at the head, achieving higher output per kilowatt compared to parallel twin-screw designs.
• Self-Wiping & Anti-Stagnation: The intermeshing flight geometry continuously cleans opposing surfaces, eliminating resin dead spots and minimizing burn-on or degradation during long production runs.
• Optimized Thermal Efficiency: Because the conical design generates consistent mechanical shear heat, external electric heating demand is minimized. Multi-zone cast-aluminum or ceramic heater bands paired with integrated cooling jackets deliver tight temperature control across all zones.
• Extended Wear Resistance: The synergy of nitrided base steel and tungsten/nickel bimetallic layers allows the assembly to operate reliably for tens of thousands of hours on heavily filled formulations without losing critical clearances.
• Custom Flight Profiles: Screw geometries (flight pitch, channel depth, decompression zones, and venting/vacuum sections) can be customized for specific applications, such as high-filler PVC pipe extrusion or delicate foam profile production.

Installation & Compatibility Notes

1. Drive Alignment: Ensure exact mechanical alignment with the extruder gearbox output shafts. Verify coupling tolerances and axial thrust bearing alignment prior to bolting.
2. Clearance Verification: Before initial startup, rotate the screw set by hand at ambient temperature to verify zero metal-to-metal contact and uniform backlash.
3. Heating & Sensor Calibration: Calibrate all zone thermocouples and inspect heater band contacts. Pre-heat the barrel assembly to processing temperature for at least 60–90 minutes to ensure uniform thermal expansion before feeding resin.
4. Venting Setup: If equipped with a degassing/vacuum port, ensure moisture traps and vacuum pump interlocks are operating properly to prevent vent-flow blockage.
5. Standard Mounting: Barrels feature standardized flange patterns (DIN/ANSI or custom OEM specifications) compatible with standard conical twin-screw extruders (e.g., SJSZ-55/110 models).

Maintenance & Lifespan

• Clearance Monitoring: Periodically check the radial clearance between the screw flight outer diameter and the barrel bore. Standard operating clearance is ~0.08–0.15 mm; refurbishment or liner replacement is recommended when wear exceeds 0.35 mm.
• Purging Protocol: Purge the extruder thoroughly with purging compound or thermal stabilizer blends immediately before shutdowns to prevent residual PVC from releasing corrosive hydrochloric acid (HCl) gas.
• Expected Lifespan: Standard nitrided barrels deliver 15,000–25,000 operating hours; premium bimetallic barrels operating on abrasive blends typically achieve 35,000–50,000+ operating hours with proper maintenance.

Safety & Quality Standards

• Manufacturing Standards: Manufactured in accordance with ISO 9001:2015 quality management and international metallurgy standards (ASTM, DIN, JIS).
• Material Certification: Delivered with complete raw material mill test reports (MTR), ultrasonic flaw detection certificates, and heat treatment hardness charts.
• Operational Safety: Ensure all thermal insulation guards, emergency-stop tripwires, and barrel pressure relief mechanisms are inspected and active during production.