PVC/WPC Hot-Cutting Pelletizing Line

Overview

The PVC/WPC Hot-Cutting Pelletizing Line is a high-efficiency conical twin-screw extrusion system engineered for multi-material granulation. With interchangeable screw designs, a single plastic pelletizer machine platform handles rigid PVC, soft PVC, WPC (wood-plastic composite), and post-industrial PVC waste recycling — eliminating the need for separate lines per material. The line integrates a pneumatic screen changer for non-stop production, a hot die-face rotary cutting system delivering uniform 3–4 mm 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, making it a reliable workhorse for compounders, profile manufacturers, and recycling operations.

Technical Parameters

Capacities measured with rigid PVC compound; actual throughput varies by material formulation and bulk density.

System Configuration

Core Features

1. Multi-Material Processing on a Single Platform

One conical twin-screw 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 depending on feedstock) and mixing element configuration — is tailored per application. For operations already running a single-screw extruder for other processes, this line complements existing capacity without duplicating material-specific machinery.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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

Step 1 — Raw Material Feeding: PVC compound (dry blend or powder), WPC pellets, or recycled PVC flakes are metered into the forced-feed hopper together with additives (stabilizers, lubricants, impact modifiers). A hopper dryer is recommended upstream for moisture-sensitive feedstocks.

Step 2 — Plasticizing & Homogenizing: Material is conveyed through the conical twin-screw barrel under controlled multi-zone heating (typically 160–195 °C for rigid PVC, lower for soft PVC). The intermeshing counter-rotating screws provide intensive shear and distributive mixing, ensuring complete homogenization before the melt reaches the filtration stage.

Step 3 — Melt Filtration: The homogenized melt passes through the pneumatic screen changer. Contaminants and gels are captured on the filter mesh. When pressure drop signals the PLC that a mesh change is due, the slide plate automatically swaps in a clean screen — all while the line continues extruding at full speed.

Step 4 — Hot Die-Face Cutting: Melt exits through a precision die plate and is cut immediately by rotary blades into cylindrical granules of 3–4 mm. Blade RPM is closed-loop controlled to match melt throughput, maintaining size uniformity across the operating range.

Step 5 — Pneumatic Conveying & Cooling: Granules are entrained in a high-velocity airstream and conveyed through ducting to a cyclone separator. Air exits the top; granules drop into the silo. An optional vacuum conveyor loader can be integrated for clean, dust-free transfer to downstream stations.

Step 6 — Collection & Packaging: Granules accumulate in the adjustable stainless steel storage silo. Operators discharge into bags, bulk containers, or connect automated conveying lines for direct feed into downstream PVC pipe extrusion or profile production.

Frequently Asked Questions

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 2.5–3.0:1 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). Screw 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-face cutting system holds 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, 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 38CrMoAlA 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 plastication. 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.

Why Choose Chenxing

Proven SJSZ Platform. The SJSZ conical twin-screw series has been deployed across hundreds of PVC and WPC production facilities worldwide. Each pelletizing line is factory-tested with customer-supplied feedstock samples before shipment, ensuring the screw configuration and process parameters are validated against your actual material.

Integrated Ecosystem. Chenxing manufactures the full upstream and downstream equipment chain — from plastic heating mixers for dry blending and hopper dryers for moisture control, through to pipe extrusion lines, roof tile extrusion lines, and embossing machines. A single-source supplier simplifies commissioning, service, and spare parts management. Browse our complete product catalog and auxiliary machines for full scope.

Recycling Expertise. For operations feeding post-industrial PVC waste, Chenxing offers integrated shredder-extruder recycling solutions that pair size-reduction equipment with this pelletizing line for a closed-loop granulation system.

Engineered-to-Order Flexibility. Screw geometry, barrel venting position, screen changer mesh specification, and control system features are configured per order — not from a fixed catalog. Visit our solutions page for application-specific configuration examples.

Global Support. Chenxing Machinery, based in Zhangjiagang City, provides remote commissioning guidance, on-site technician dispatch, and lifetime technical support. Learn more about us and keep up with the latest news and case studies.

Start Your Inquiry in 4 Steps

Step 1 — Tell Us Your Material: Specify your feedstock — rigid PVC compound, soft PVC formulation, WPC (wood flour loading % and polymer base), or recycled PVC (source, contamination level, particle size).

Step 2 — Define Your Output Target: Desired throughput in kg/h and preferred model range (SJSZ51 through SJSZ92).

Step 3 — Receive a Custom Proposal: Our engineering team reviews your requirements and provides a tailored configuration — screw design, screen changer spec, and auxiliary equipment recommendations — typically within 24 hours.

Step 4 — Validate with a Sample Run: Optionally send 50–100 kg of your feedstock for a trial run at our Zhangjiagang factory. We record granule quality, throughput data, and energy consumption for your evaluation before commitment.

Contact Nicole directly:

• Phone WeChat WhatsApp: +8615951187228

• Email: ceo@cxsljx.com

Or visit our contact page for the full inquiry form. We respond to all inquiries within one business day.