Side Force Feeder PE/PP Film Pelletizing Line — Anti-Bridging Recycling Granulator

The Problem with Recycled Film — Why Gravity Feeders Fail

Recycled PE and PP film is one of the most abundant and economically attractive feedstocks in plastic recycling. Post-consumer LDPE stretch film, HDPE grocery bags, LLDPE agricultural mulch, PP woven bags — millions of tons are collected, washed, and dried annually. The material is available at $0.30-0.70/kg depending on grade and cleanliness, and the demand for recycled PE/PP pellets — from blown film extrusion, injection molding, and pipe production — is immense and growing under recycled-content mandates.

But between washed film flake and a saleable pellet sits a problem that has frustrated recyclers for decades: washed film flake does not feed.

The physics are unforgiving. Washed PE/PP film flake — typically 20-50mm irregular pieces, thin (10-100 microns), and curled from the washing and drying process — has a bulk density of 80-150 kg/m3. That is one-tenth to one-fifth the bulk density of virgin pellets (550-650 kg/m3). In a standard gravity-feed hopper, this low-density material does not "flow" — the flakes interlock, bridge across the hopper throat, and resist gravity. The extruder screw, designed to receive a consistent polymer melt at the feed zone, instead receives intermittent slugs of material interspersed with voids.

The downstream consequences cascade through the entire pelletizing line:

• Feed instability: The extruder screw alternately starves and floods. Motor current fluctuates wildly. Melt pressure oscillates. The extruder never reaches steady-state operation.

• Output fluctuation: Throughput varies 20-40% minute to minute as the feed bridges, collapses, and bridges again. Rated capacity is theoretical — actual sustained output is far lower.

• Inconsistent pellet quality: Fluctuating melt pressure produces pellets with varying density, shape, and residual stress. Downstream processors see surging, color variation, and mechanical property inconsistency.

• Operator dependency: An operator must stand at the hopper with a stick, constantly poking, prodding, and forcing material into the screw. "Hopper poker" is the recycler's unofficial job title — and it turns a supposedly automated process into a labor bottleneck.

• Energy waste: The extruder, heater, and downstream equipment consume near-rated energy even when throughput is far below rated capacity. Energy cost per kilogram of pellet produced rises as effective throughput drops.

These problems are not new. They are inherent to gravity feeding of low-bulk-density materials. The solution is not a taller hopper, a wider throat, or a more powerful screw. The solution is to stop relying on gravity.

How the Side Force Feeder Solves Film Feeding

The Side Force Feeder is the Chenxing CX-SFF pelletizing line's core innovation — and the reason this line achieves stable, high-throughput film recycling where conventional single-screw lines fail.

The Physics of Forced Feeding vs. Gravity Feeding

In a conventional gravity-feed system, material moves into the extruder because gravity pulls it downward. For dense, free-flowing pellets, this works: bulk density is high, inter-particle friction is low, and gravity provides consistent motive force. For washed film flake, gravity cannot overcome the interlocking and bridging. The material arches across the hopper throat — a stable mechanical bridge that supports the weight above it — and flow stops until the bridge is broken (manually, with a stick).

The Side Force Feeder replaces gravity with mechanical displacement. Here is the process step by step:

1. Screw Feeder Intake: Washed film flake is loaded — manually or by conveyor — into a primary screw feeder. This screw feeder meters the material at a controlled rate, providing the first level of feed rate control. Unlike a hopper, the screw feeder is a positive-displacement device: each revolution moves a fixed volume of material, regardless of bulk density.
   

2. Side Force Feeder — Positive Displacement into the Extruder: The screw feeder discharges directly into the Side Force Feeder — a second, short, powerful screw mounted at a right angle to the main extruder. This side screw receives material from the metering feeder and forces it into the extruder feed throat under mechanical pressure. There is no gap for bridging. The side screw's flights physically push the film flake into the extruder screw's flights, ensuring every rotation of the main extruder screw receives a full charge of material.
   

3. Extruder Receives Consistent Feed: With material positively displaced into the feed zone on every revolution, the extruder operates at steady-state melt pressure. The screw is always full. Motor current is stable. Throughput is predictable and consistent.

The Quantitative Difference

The difference is not incremental — it is transformational. The Side Force Feeder converts film recycling from a labor-intensive, low-efficiency process into a stable, automated, high-throughput operation. For recyclers who have struggled with film feeding, the experience of operating a CX-SFF line — pressing a button and watching consistent pellets emerge, hour after hour, without a hopper poker — redefines what film recycling means.

CX-SFF Series Technical Specifications

The CX-SFF is built around the SJ120/25 single-screw extruder platform, with capacity customizable through screw diameter and configuration to meet throughput requirements from 60 to 1000 kg/h. It is a single-model series: all CX-SFF lines share the Side Force Feeder core, 38CrMoAlA screw and barrel, electromagnetic heating, high-speed screen changer, and dual pelletizing option. The screw diameter, motor power, and downstream equipment are sized to the target capacity.

Core Specifications

Process Flow — Water-Ring Pelletizing Route

Screw Feeder → Side Force Feeder → SJ120/25 Extruding System     → High Speed Screen Changer & Die Head → Water-Ring Pelletizer     → Dewatering Machine → Vibrating Screen → Air Blower System → Silo

The water-ring route is optimized for high-capacity continuous production. Molten polymer exits the die head into a rotating water ring that cools and cuts pellets simultaneously. The water quench solidifies the pellet surface instantly, preventing pellet agglomeration. A dewatering machine and vibrating screen separate and classify pellets. Air conveying delivers finished pellets to the storage silo.

Process Flow — Strand Pelletizing Route

Screw Feeder → Side Force Feeder → Extruding System     → High Speed Screen Changer & Die Head → Water Cooling Tank     → Air Dryer → Strand Pelletizer → Vibrating Screen     → Air Blower System → Storage Silo

The strand route is preferred for lower-volume operations, frequent material changeovers, and applications where pellet shape requirements are specific. Molten polymer strands exit the die head into a water cooling bath, solidify, pass through an air dryer to remove surface moisture, and enter a rotating-knife strand pelletizer that cuts the strands into cylindrical pellets. The strand route offers easier visual quality inspection — operators can see the strands before cutting — and simpler cleaning between material grades.

Key Advantages of CX-SFF Pelletizing Line

Side Force Feeder — The End of Hopper Poking

• Feature: A secondary, mechanically driven side screw that positively displaces low-bulk-density film flake into the extruder feed throat, replacing gravity with controlled mechanical feed.

• Advantage: Washed film flake at 80-150 kg/m3 bulk density cannot flow under gravity — it bridges, arches, and starves the extruder. Every recycler knows the solution: stand at the hopper with a stick, poking material into the screw. The Side Force Feeder replaces this human intervention with a short, powerful screw that forces material into the extruder on every rotation. The metering screw feeder feeding the side force feeder provides the first control stage; the side force feeder provides the second — positive displacement into the extruder. The result is a full extruder screw on every rotation, stable melt pressure, and consistent throughput.

• Benefit: Throughput variation reduced from ±20-40% (gravity) to ±3-5% (side force). Rated capacity is achieved — not just specified. The extruder operates at its design point continuously. Pellet weight, density, and shape are consistent from the first pellet to the millionth. And no operator stands with a stick — the line runs itself.

38CrMoAlA Nitride-Hardened Screw with Alloy Feed Zone — Built for Abrasive Film

• Feature: Screw and barrel manufactured from 38CrMoAlA alloy steel, nitride-hardened to 900-1000 HV surface hardness. Feed zone additionally treated with special wear-resistant alloy to withstand the abrasive friction of film flake.

• Advantage: Film recycling is abrasive — even washed flake carries microscopic grit, and the thin, high-surface-area film generates high friction in the feed zone. A standard nitrided screw (typically 700-800 HV) wears prematurely in the feed zone, losing compression efficiency. The 38CrMoAlA screw with nitride hardening delivers 900-1000 HV surface hardness, and the alloy-treated feed zone adds a second layer of abrasion resistance precisely where wear is concentrated. This is the same material specification used in premium compounding extruders processing filled polymers.

• Benefit: Extended screw life — 3-5 years of continuous film recycling duty before screw replacement. Maintained compression ratio and plastication quality over the screw's service life. Consistent melt quality year after year — no gradual degradation from feed zone wear. Lower screw replacement cost amortized over longer service intervals.

Electromagnetic Heating — 30-40% Energy Reduction

• Feature: Electromagnetic induction heaters replace traditional resistance band heaters on all barrel zones. Heating is through eddy-current induction directly into the barrel wall rather than through contact conduction from a resistance element.

• Advantage: Resistance band heaters lose 20-40% of their input energy to the ambient air — the heater band is hotter than the barrel, and the heat loss path is direct. Electromagnetic heaters induce current directly in the barrel wall, and the barrel itself becomes the heating element. No thermal contact resistance. No hot band exposed to ambient air. The barrel heats faster (minutes instead of tens of minutes), temperature control is more precise (±1°C vs. ±3-5°C for resistance), and energy consumption drops 30-40%. The heater surface remains cool to the touch — no burn hazard, no contribution to the factory's heat load.

• Benefit: For a line consuming 100-200 kW in heating, a 30-40% energy reduction saves 0.10/kWh, 6000 operating hours). The energy saving alone pays for the upgrade from resistance to electromagnetic heating within the first year. Faster startup reduces non-productive warm-up time. More precise temperature control improves melt quality.

High-Speed Non-Stop Screen Changer — No Downtime for Filtration

• Feature: Hydraulic high-speed screen changer that swaps filter screens in under one second without stopping extrusion or breaking the melt strand.

• Advantage: Recycled film, even after washing, contains residual contaminants — paper labels, adhesive residue, and fine grit — that accumulate on the screen pack. In a standard manual screen changer, the extruder must stop to replace screens — stopping the entire downstream line. Production stops. The melt cools. Restart wastes material and time. The CX-SFF's hydraulic high-speed changer swaps screens while the extruder runs at full speed. The operator initiates the change; the hydraulic cylinder slides the clean screen into position and ejects the dirty screen; the melt flow is uninterrupted.

• Benefit: Continuous production — zero downtime for screen changes. Consistent filtration — the screen is changed when dirty, not deferred to the next scheduled stop. Reduced scrap from startup/shutdown cycles. Higher effective operating hours per year.

Dual Pelletizing — Water-Ring and Strand on One Platform

• Feature: The CX-SFF accommodates both water-ring (high-capacity) and strand (flexible) pelletizing as interchangeable downstream modules.

• Advantage: No single pelletizing technology is optimal for all recycling operations. Water-ring pelletizing delivers high throughput with automated pellet-water separation — ideal for a recycler running 500-1000 kg/h of a single material. Strand pelletizing offers easy visual quality inspection, simple cleaning between materials, and the ability to cut cylindrical pellets to specification — ideal for lower-volume operations processing multiple materials or grades. The CX-SFF accepts either module on the same extruder platform.

• Benefit: One extruder platform serves the recycler's needs as they evolve. Start with strand pelletizing for flexibility; upgrade to water-ring as volume grows. No extruder replacement required — just change the downstream module. Lower capital risk; higher operational flexibility.

Fully Automated — One Operator, One Line

• Feature: PLC-based automatic control with constant-temperature regulation, inverter-driven speed control, and automatic alarm/stop on process deviation. After initial setup, the line runs with 1-2 workers for material loading and finished-pellet hopper change.

• Advantage: The film recycling pelletizing line integrates feeding, extrusion, filtration, pelletizing, dewatering/drying, screening, and conveying into a single automated sequence. The PLC maintains temperature zones within ±1°C, adjusts screw speed via inverter to match feed rate, and monitors melt pressure and motor current. If any parameter deviates from the set range, the PLC alarms and, if necessary, safely stops the affected section. The operator's role is material logistics — not process control.

• Benefit: Labor cost of 1-2 workers per line — the lowest in the industry for film recycling. Consistent product quality independent of operator skill or attention. Lower training requirement — operators learn material handling, not extrusion engineering. Scalable: add more lines without proportionally adding staff.

Low-Noise Drivetrain — A Quieter Factory Floor

• Feature: Redesigned gearbox and motor coupling with noise-reducing tooth profiles and isolation mounting.

• Advantage: Extruder gearboxes are a primary noise source in recycling plants. The CX-SFF's redesigned transmission reduces gear mesh noise through optimized tooth profiles that maintain constant-velocity contact, and vibration-isolating mounts that prevent structure-borne noise transmission to the factory floor.

• Benefit: Measurably lower noise levels — compliant with workplace noise regulations without acoustic enclosures. Better working conditions for operators. Reduced noise complaints in mixed-use industrial areas. The noise reduction is a quality-of-life improvement that operators notice immediately.

Compact, Integrated Design — One Supplier, One Responsibility

• Feature: All components — feeding, extrusion, filtration, pelletizing, dewatering/drying, screening, and conveying — are designed, manufactured, and integrated by Chenxing Machinery as a single-system supplier.

• Advantage: Multi-vendor pelletizing lines create integration risk: the feeder from one supplier, the extruder from another, and the pelletizer from a third must work together seamlessly. When they don't — and they often don't — responsibility diffuses among suppliers. The CX-SFF avoids this by delivering a complete, pre-integrated line from a single manufacturer. Every component is engineered to work with every other component, and Chenxing takes full responsibility for the line's performance.

• Benefit: One installation. One commissioning team. One supplier to call for any issue. Faster resolution. Clear accountability. The relationship between Chenxing and the recycler is direct and undiluted.

Choosing Between Water-Ring and Strand Pelletizing

Recommendation:

• Choose Water-Ring if you process >300 kg/h of a single material or grade, run continuously, and prioritize throughput over flexibility.

• Choose Strand if you process <300 kg/h, run multiple materials or grades, need frequent cleanout between batches, or want to visually inspect melt quality before cutting.

Both modules are available for the CX-SFF platform. Chenxing supplies the complete line with either configuration, and retrofitting from strand to water-ring (or vice versa) is supported if your needs change.

Material Compatibility & Pellet Quality Guide

Feedstock Quality Requirements

• Cleanliness: Film must be washed and dried. Residual dirt, labels, or adhesive residues pass through the screen changer (which protects the die) but become pellet contaminants that reduce value.

• Moisture: <1% moisture. If film has been washed and stored, pre-dry with an STG-U hopper drier at 80°C for 2 hours before feeding.

• Metal Contamination: A CJ magnetic frame on the feed conveyor captures ferrous metal before it reaches the extruder.

• Pre-crushing: For woven bags and thick film (>200 microns), pre-crush with a plastic crusher to <100mm pieces for optimal side force feeder performance.

Frequently Asked Questions

Why does standard gravity feeding fail with washed film flakes?

Washed film flakes have a bulk density of 80-150 kg/m3 — roughly one-sixth that of virgin pellets. At this density, gravity cannot overcome the inter-particle friction that causes flakes to interlock and form mechanical bridges across the hopper throat. The bridge supports the weight of material above it, and flow stops. Breaking the bridge — manually, with a stick — is the only solution in a gravity-fed system. The problem is not hopper design or flake quality — it is physics. The Side Force Feeder solves it by eliminating gravity as the feed mechanism and replacing it with positive mechanical displacement.

How much more throughput can I get with a side force feeder?

Recyclers switching from a gravity-fed single-screw line to the CX-SFF with Side Force Feeder typically see effective throughput increase from 50-70% of rated capacity to 90-100%. For example, a line rated at 500 kg/h with a gravity hopper might sustain 250-350 kg/h in film service. The same extruder with Side Force Feeder sustains 450-500 kg/h — a 40-100% increase in effective output from the same screw and motor. The improvement is largest for LDPE and LLDPE (lowest bulk density, worst bridging) and smallest for HDPE (higher stiffness, less bridging). The throughput gain alone typically justifies the Side Force Feeder investment within months.

Can this line process both PP and HDPE film?

Yes — the CX-SFF processes all common PE and PP film grades (LDPE, LLDPE, HDPE, and PP) as well as clean PP woven bags and non-woven bags. The extruder temperature profile and screw speed are adjusted to suit each material: PE processes at 160-230°C, PP at 190-240°C. Material changeover requires purging the extruder and cleaning the screen changer — approximately 30-60 minutes. For operations processing multiple materials regularly, the strand pelletizing route simplifies changeover — the water bath is dry and easily cleaned, and strands are visually inspected before cutting.

What is the difference between water-ring and strand pelletizing?

Water-ring pelletizing cuts molten polymer in a rotating water ring at the die face — the water simultaneously cools and transports pellets. It is a compact, automated process optimized for high-capacity continuous production (300-1000 kg/h). Strand pelletizing extrudes strands into a water cooling bath, dries them, and cuts them in a separate rotating-knife cutter. It is more flexible — operators can see strand quality before cutting, changeover between materials is faster, and initial equipment cost is lower. The strand route is preferred for lower capacities (60-500 kg/h) and multi-material operations. The CX-SFF accommodates either module.

How does electromagnetic heating reduce my electricity bill?

Electromagnetic induction heaters deliver energy directly into the barrel wall through eddy currents — the barrel becomes the heating element. In resistance band heaters, the element heats the band, and the band transfers heat to the barrel through contact — with 20-40% of the heat lost to ambient air through the band's outer surface. Electromagnetic heaters eliminate this loss path because there is no hotter element radiating outward. The 30-40% energy reduction translates to $15,000-40,000 annual savings for a typical recycling line. Additionally, the heater outer surface stays cool (<50°C), reducing factory heat load and air conditioning cost in summer, and eliminating the burn hazard of exposed hot bands.

How many workers are needed to operate this line?

After initial setup and temperature stabilization, the CX-SFF requires 1-2 workers per shift. Their tasks are material logistics — loading washed flake into the screw feeder hopper, changing finished-pellet collection bins or hoppers, and monitoring the control panel for alarms. One worker handles both input and output sides at lower capacities (60-300 kg/h). Two workers are recommended at higher capacities (>300 kg/h) — one for material loading, one for pellet handling. The PLC manages temperature, speed, melt pressure, and screen change automatically. No operator is required to stand at the hopper — the Side Force Feeder eliminates the hopper poker role entirely.

What is the typical payback period for a film recycling pelletizing line?

For a recycler processing 2,000 tons of washed film annually, selling recycled PE pellets at 0.30-0.60/kg, the value uplift from pelletizing is 35,000-60,000 depending on capacity and options. Simple payback: 1-3 months on the value uplift alone, even shorter if energy savings and labor reduction are included. For recyclers who have been selling flake and considering backward integration into pelletizing, the return on investment is compelling enough that many order additional lines within the first year of operation.

Start Recovering Value from Your Film Waste Today

Step 1 — Characterize Your Feedstock: Identify your primary material (LDPE LLDPE HDPE PP mixed), annual volume, flake form (washed, size, bulk density), and target pellet application. This determines the optimal screw configuration, capacity, and pelletizing route.

Step 2 — Select Your Configuration: Our engineering team maps your feedstock to the optimal CX-SFF configuration — screw diameter, motor power, heating system, pelletizing module, and optional pre-treatment equipment (crusher, dryer, magnet). We provide a complete line proposal with specifications, floor plan, and pricing.

Step 3 — Contact Nicole for a Quote: Send your feedstock details and target capacity to Nicole. We will prepare a tailored quotation within 24 hours, including equipment, installation, commissioning, and training.

Step 4 — Install, Commission, and Start Producing: Chenxing provides on-site installation supervision, commissioning, operator training, and a spares kit. After commissioning, your line runs with 1-2 operators — producing consistent, high-quality recycled PE/PP pellets from the first day. Our after-sales team provides ongoing support, and spare parts ship within 48 hours.

For complementary equipment, explore Chenxing's full recycling range: plastic crushers for pre-crushing, CJ magnetic frames for metal protection, STG-U hopper driers for pre-drying, and high-speed mixers for post-production blending. If your recycling process includes powder grinding, see our SMF disc grinding pulverizer and SMP knife pulverizer series for PE, PP, and other material powder production.

Contact Chenxing Machinery Today:

• Contact Person: Nicole

• Phone / WhatsApp: +8615951187228

• Email: ceo@cxsljx.com

• Company: Zhangjiagang Chenxing Machinery Co., Ltd.

• Website: www.chenxingmachinery.com