PVC/WPC Hot-Cutting Pelletizing Line
The SJSZ PVC/WPC Hot-Cutting Pelletizing Line is a high-efficiency conical twin-screw extrusion system engineered for multi-material granulation. This plastic pelletizer machine platform handles rigid PVC (uPVC), soft PVC (plasticized), WPC (wood-plastic composite), and post-industrial PVC waste recycling — eliminating the need for separate production lines per material.
★ Key Specifications: Granule Size: 3–4 mm (±0.3 mm) | Drive Power: 18.5–90 kW | Capacity: 80–800 kg/h | Screw Type: Conical Twin-Screw | Control: PLC-based with Touchscreen HMI
The line integrates a pneumatic screen changer for non-stop production, a hot die-face rotary cutting system delivering uniform granules, strong-wind pneumatic conveying with cyclone separation for rapid cooling, and an adjustable stainless steel storage silo. Built on the proven SJSZ conical twin-screw architecture, it delivers stable high-speed extrusion over extended production runs.
Parameter of PVC/WPC Hot-Cutting Pelletizing Line:
Initiate Your Project Now
Core Features & Competitive Advantages of PVC/WPC Hot-Cutting Pelletizing Line:
Multi-Material Processing on a Single Platform
One conical twin-screw extruder design processes four distinct material categories: rigid PVC (uPVC), soft PVC (plasticized), WPC formulations, and post-industrial PVC waste for recycling. Screw geometry — including compression ratio (typically 2.5:1 to 3.5:1) and mixing element configuration — is tailored per application. For operations already running a single-screw extruder, this line complements existing capacity without duplicating material-specific machinery.
Non-Stop Production with Pneumatic Screen Changer
The integrated pneumatic screen changer uses a slide-plate mechanism that swaps contaminated filter screens in under 30 seconds without halting extrusion. Melt pressure is maintained during the changeover cycle. This eliminates the 5–15 minute downtime typical of manual screen changes, directly improving OEE (Overall Equipment Effectiveness) and reducing material waste from start-up purging.
Hot Die-Face Cutting for Uniform 3–4 mm Granules
Rotary blades cut melt strands directly at the die face while the material is still hot, producing cylindrical granules with tight size tolerance (±0.3 mm). Blade speed is synchronized with extruder output via the PLC to maintain dimensional consistency across the full throughput range. The die plate features hardened tool steel inserts for extended service life under abrasive formulations.
Rapid Cooling via Strong-Wind Conveying & Cyclone Separation
Freshly cut hot granules enter a high-velocity airstream immediately after cutting. The cyclone separator decouples granules from conveying air, achieving surface cooling sufficient to prevent agglomeration before the granules reach the storage silo. For temperature-sensitive formulations, an optional SML series chiller can pre-cool the conveying air for additional thermal control.
Adjustable Stainless Steel Storage Silo
The SUS304 stainless steel collection silo features an adjustable discharge gate and a transparent inspection window for level monitoring. A pellet vacuum loader can be mounted on the silo outlet for automated transfer to packaging stations, intermediate bulk containers, or downstream mixing equipment such as a plastic heating mixer for masterbatch blending.
Long-Time Stable High-Speed Extrusion
Forced barrel cooling (air or water-cooled zones with PID regulation), a hardened bimetallic barrel, and nitrided alloy steel screws enable continuous high-speed operation. The conical twin-screw architecture inherently provides higher torque capacity and shorter residence time compared to parallel twins, reducing thermal degradation risk during extended runs — critical for heat-sensitive rigid PVC formulations.
Production Process Flow of PVC/WPC Hot-Cutting Pelletizing Line:
Frequently Asked Questions (FAQ):
Q1: Can this line process both rigid PVC and WPC on the same screw?
The SJSZ series accommodates both materials, but optimal results require dedicated screw configurations rather than a single universal screw.
Rigid PVC (uPVC) benefits from a compression ratio of approximately 2.5:1 to 3.0:1 with mixing elements optimized for thermal sensitivity — melt temperatures are typically maintained at 160–195 °C across 6–8 barrel zones. WPC formulations (typically 50–70% wood flour loading) demand a compression ratio of 3.0–3.5:1, deeper feed-zone channels to handle lower bulk density, and tighter temperature control (max 170–180 °C) to prevent wood flour charring.
Screen changeover between materials takes approximately 2–3 hours with the quick-change coupling design. For operations regularly switching between these materials, we recommend maintaining separate screw-and-barrel sets calibrated for each feedstock, effectively giving you two production lines on one drive platform.
Q2: How consistent is the 3–4 mm granule size, and what affects cutting precision?
Granule size consistency is primarily governed by three interacting variables: blade tip speed (RPM), melt viscosity at the die exit, and extruder output rate. Under stable operating conditions, the hot die-cutting system yields granules within a ±0.3 mm tolerance band.
Blade speed is electronically synchronized with screw RPM via the PLC; when extruder output ramps from 150 to 500 kg/h (SJSZ80/156), blade RPM increases proportionally to maintain the target 3–4 mm cut length.
The dominant disturbance is melt viscosity fluctuation — a ±5 °C variation in die-head temperature can shift melt flow and produce granules at the tolerance boundary. For this reason, the PID temperature controllers on the die zone and adaptor are tuned to a ±1 °C setpoint deviation, and operators should avoid feedstock batch changes mid-run that introduce viscosity swings. Blade sharpness also matters: dull blades tear rather than cut, broadening the size distribution.
Q3: How does the pneumatic screen changer work without stopping production?
The screen changer uses a hydraulic or pneumatic slide-plate mechanism that moves a pre-loaded filter mesh carrier into the melt stream while simultaneously ejecting the contaminated screen. Melt pressure — typically 10–25 MPa at the screen changer inlet for rigid PVC — is maintained throughout the cycle because the slide plate seals against upstream melt immediately upon actuation. The full mesh swap completes in 15–30 seconds, during which a transient pressure fluctuation of ±0.5–1.0 MPa may register on the head-pressure transducer but does not disrupt downstream cutting.
Key to reliability: the carrier plate employs a dual-seal design (metal-to-metal primary seal plus polymer backup ring) that prevents melt leakage during the slide stroke. Screen mesh specification depends on contamination load: 80–120 mesh works well for virgin rigid PVC compound; coarser 40–60 mesh is standard for recycled PVC feedstock with higher particulate burden. Operators replace the fouled mesh offline while the clean screen continues filtering.
Q4: What screw L/D ratio is recommended for waste PVC recycling vs. virgin rigid PVC?
For virgin rigid PVC on a conical twin-screw, the effective L/D typically ranges from 16:1 to 20:1, with a compression ratio of approximately 2.5–3.0:1. This provides adequate residence time for complete gelation without over-shearing the heat-sensitive material.
For post-industrial PVC waste recycling — where feedstock may include profiles, pipe regrind, or mixed rigid scrap — we recommend pushing the effective L/D to 20:1–22:1 with a compression ratio of 3.0–3.5:1. The extended length accommodates a longer feed and compression zone to handle variable bulk density and inconsistent particle morphology.
Degassing capacity also becomes critical: recycled PVC may carry residual moisture and volatiles, so the vacuum venting zone (typically positioned at 60–70% of barrel length from feed) must be sized for higher vapor load.
All SJSZ series screws are manufactured from nitrided 38CrMoAl alloy steel with a surface hardness of HV 900–1000, providing adequate wear resistance for the mildly abrasive nature of recycled feedstock.
Q5: What is the typical energy consumption per ton of output?
For rigid PVC pelletizing on the SJSZ series, specific energy consumption ranges from 0.25 to 0.35 kWh/kg (250–350 kWh per ton), varying by model size and throughput.
The SJSZ80/156 operating at its nominal 375 kg/h midpoint typically draws approximately 0.28–0.30 kWh/kg, meaning roughly 280–300 kWh to produce one metric ton of finished granules. This figure covers the extruder main drive, barrel heaters (6–8 zones, each 2–4 kW), die-head heating, hot-cut motor, blower, and vacuum pump.
Larger models trend toward the lower end of the range due to improved thermal efficiency: at 650 kg/h the SJSZ92/188 achieves approximately 0.26–0.28 kWh/kg.
By comparison, a high-output single-screw extruder of equivalent throughput may consume 0.30–0.40 kWh/kg for PVC compounding due to less efficient plasticization. All SJSZ drive motors are IE3 premium efficiency as standard (IE4 optional). For operations seeking to benchmark energy costs, multiply your local electricity tariff by 0.30 kWh/kg as a conservative planning figure for rigid PVC.
