An LFT-G extrusion line (“G” for granules) converts thermoplastic resin and continuous fiber rovings into long-fiber reinforced pellets through a continuous process. It combines a resin-melt path with a continuous-fiber path; the two materials converge in the impregnation die before the composite strands are cooled, pulled, cut, and screened.
The required resin, fiber package, fiber content, output, and pellet specification determine how these sections are configured. The same output target can therefore require different equipment arrangements for different material systems.
What Shapes the Line Configuration?
A long fiber reinforced thermoplastic (LFT) pelletizing line is configured around the compound to be produced and the output required. The following requirements directly affect equipment selection and line layout:
| Project Requirement | Configuration Decision |
| Resin grade, processing range, and moisture sensitivity | Extruder, melt-transfer, and impregnation-die temperature range, heating capacity, drying arrangement, and thermal-control requirements |
| Melt-flow behavior and thermal stability | Screw and barrel configuration, residence-time control, feeding accuracy, and operating window |
| Fiber type, sizing, tex, and bundle construction | Fiber pretreatment, spreading width, tension range, die-entry geometry, and impregnation conditions |
| Fiber package dimensions, core type, and winding pattern | Creel layout, loading method, inside or outside unwinding, and tension-control arrangement |
| Target fiber content | Resin-to-fiber metering ratio, strand configuration, die outlets, and line-speed coordination |
| Additives and modifiers | Feeding arrangement, dosing accuracy, melt-processing window, and any required premixing or dispersion stage |
| Required output | Extruder capacity, number of strands, cooling capacity, haul-off, and pelletizing throughput |
| Pellet length and quality requirements | Traction-and-cutter synchronization, pelletizer configuration, screening, conveying, and storage handling |
| End-use and downstream processing requirements | Defines pellet-length consistency, fiber-content control, screening, handling, and quality-record requirements |
Select the Extruder and Melt-Preparation System
The extruder and melt-preparation system form the resin side of the LFT-G extrusion process. They prepare a stable polymer melt from the selected resin formulation.
| Resin-Side Element | What to Specify | Why It Matters |
| Resin and additive feeding | Resin form, target resin throughput, additive type, dosing ratio, and whether materials are premixed or separately fed | Determines feeder type, number of dosing units, and metering accuracy required |
| Material conditioning | Moisture sensitivity, drying requirement, and handling conditions before feeding | Helps prevent moisture-related processing issues and unstable melt quality |
| Twin-screw extruder | Resin processing range, melt viscosity, required resin throughput, thermal sensitivity, and additive package | Determines extruder size, screw and barrel configuration, drive torque, heating and cooling capacity, and operating range |
| Melt transfer to the die | Required melt temperature, pressure stability, and connection layout | Ensures the impregnation die receives a consistent melt supply |
A loss-in-weight feeder provides controlled resin dosing, while the twin-screw extruder plasticizes and homogenizes the formulation before transferring melt to the impregnation die.
Prepare the Fiber Before Impregnation
The fiber side of an LFT-G extruder line must deliver continuous rovings to the impregnation die at stable tension and in a condition that supports efficient wet-out. The unwinding system should match the roving package, including its payout direction, core structure, size, weight, winding pattern, and required delivery rate.
| Unwinding Approach | Typical Package Situation | Primary Function |
| Unpowered outside unwinding | Small paper-core packages and selected carbon-fiber packages | Uses adjustable pretension to control passive payout |
| Damped outside unwinding | Larger paper-core glass-fiber packages, basalt fiber, and selected polymer-fiber packages | Adds rotational damping to stabilize payout from heavier packages |
| PLC-controlled powered inside unwinding | Large glass-fiber packages designed for internal payout | Uses motor-driven payout synchronized with production rate |
Fiber Pretreatment: Spreading and Preheating
Before entering the impregnation die, the roving can be spread to reduce the distance molten polymer must travel through the fiber bundle. The spreading width should be adjustable for the fiber type and roving format. Preheating brings the fiber closer to melt temperature, reducing the risk that a cold roving will rapidly cool the polymer at die entry; this helps maintain impregnation conditions and can reduce fiber-breakage risk.
Configure the Impregnation Die for Stable Wet-Out
The impregnation die is where the molten polymer meets the prepared continuous rovings. It must guide the fiber and distribute melt through the bundle to form stable composite strands before cooling.
Because thermoplastic melts are relatively viscous, wet-out depends on melt viscosity, pressure, fiber-bundle structure, pulling speed, fiber tension, and die-flow geometry. The die must balance these conditions rather than maximize any one of them.
| Die Design Objective | What Must Be Balanced | If Poorly Balanced |
| Improve impregnation | Melt flow path, pressure, viscosity, and contact time | Incomplete wet-out, voids, or uneven resin distribution |
| Limit fiber breakage | Fiber guidance, tension, melt-flow resistance, and pulling speed | Fiber damage, unstable strand travel, or frequent breaks |
| Avoid polymer degradation | Melt temperature, avoidance of stagnant melt zones, and residence time | Excessive thermal exposure or degraded melt quality |
| Maintain line efficiency | Line speed, impregnation performance, and strand quantity | Lower output or inconsistent strand quality |
| Keep strands consistent | Melt distribution and fiber paths across all die outlets | Strand-to-strand variation in wet-out or pellet quality |
For multi-strand production, comparable melt flow and fiber guidance are needed at every outlet.
Cool, Pull, and Pelletize the Composite Strands
After impregnation, the composite leaves the die as continuous strands. The downstream section cools and stabilizes those strands, removes surface water, guides them into an orderly path, and converts them into finished pellets.
| Downstream Stage | Main Function |
| Cooling water tank | Reduces strand temperature and stabilizes the composite after impregnation |
| Strand shaping | Stabilizes strand geometry before downstream handling |
| Blower or drying unit | Removes residual surface water before cutting |
| Strand arranging | Separates and guides multiple strands into the haul-off and cutter |
| Haul-off | Conveys the strands through the downstream section |
| Pelletizer | Cuts strands into pellets at the set length |
| Vibrating screen | Separates fines or irregular pellets from the finished material |
Traction System Selection
The haul-off should be selected for the actual strand quantity and installation layout. Compact pneumatic rubber-roller haul-off units can suit multi-strand lines where floor space is limited, while track-style haul-off units apply more uniform pressure across each strand and can be used for larger pilot or production systems where more space is available.
Pelletizing and Screening
The pelletizer provides stable, adjustable cutting for cooled strands, while screening separates out-of-specification pieces before the material moves to collection or packaging. Chuangbo’s dual-drive pelletizing arrangement uses independently driven haul-off and cutter motors.
PLC-Based Line Control and Production Monitoring
An LFT-G production line must keep resin feeding, fiber delivery, traction, and pelletizing aligned as production conditions change. Chuangbo’s PLC-based control system allows operators to set key production parameters, including the polymer system, fiber type, number of rovings, target fiber content, line speed, and pellet length.
| Control Function | Production Value |
| Recipe-based parameter setting | Establishes coordinated operating conditions for the selected resin, fiber, fiber content, line speed, and pellet length |
| Start-up inspection and controlled ramp-up | Checks line status before operation and brings the line to the selected production speed in a coordinated sequence |
| Linked feed, traction, and cutting control | Keeps resin feeding, fiber delivery, traction speed, and cutting conditions aligned as the line speed changes |
| Production-data display | Provides visibility into total output, polymer consumption, fiber consumption, line speed, and pelletizing status |
| Fiber-package monitoring | Estimates remaining fiber length and supports timely roving changeover when the selected unwinding configuration includes this function |
| Operator adjustment | Allows controlled single-parameter adjustments when on-site conditions require process correction |
Together, these functions give operators one control point for starting, monitoring, and adjusting the line during production.
Agree Acceptance Criteria Before Manufacturing
Agree acceptance criteria before equipment manufacturing begins. They provide a shared basis for line design, factory testing, commissioning, and final handover.
| Acceptance Area | What to Agree Before Manufacturing |
| Resin and fiber system | Resin grade, fiber type, sizing, and relevant formulation conditions |
| Output | Target kg/h and the operating conditions used during the test |
| Fiber content | Target range, sampling approach, and measurement method |
| Pellet length | Target range and permitted variation |
| Pellet quality | Pellet appearance, cut consistency, fines level, and screening requirements |
| Trial operation | Test duration, stability requirements, and agreed test procedure |
| Production records | Parameters, output data, and material-consumption records to be documented |
| Downstream validation | Responsibility for molding trials and final-part testing |
The line can be assessed against agreed production and pellet-quality criteria. Final molded-part performance should be validated separately because it also depends on the formulation, mold, molding machine, processing conditions, and part design.
Tailored LFT-G Extrusion Solutions from Chuangbo
Chuangbo manufactures LFT-G extrusion lines for continuous production of long fiber reinforced thermoplastic granules. Each line can be configured around the selected resin, reinforcement fiber, fiber content, additive requirements, output, strand arrangement, and pellet specification.
Explore Chuangbo’s LFT-G extrusion line or reach out directly to discuss your production requirements.
