PVC Profile Extrusion Line Process

PVC (polyvinyl chloride) profiles are widely used in building doors and windows, decorative moldings, curtain wall frames, electrical conduits, and other fields due to their excellent weather resistance, heat insulation, flame retardancy, and recyclability. An efficient and stable PVC profile extrusion production line is crucial for ensuring product quality and production efficiency.

I. Raw Material Preparation and Mixing

1. Raw Material Composition
PVC profiles typically use a powder-based formulation system, with the main components including:

PVC resin (SG-5 or SG-7 type, K value 65–68);
Heat stabilizers (calcium-zinc, organotin, or lead salts; currently trending towards lead-free);
Processing aids (ACR type, improving melt strength and plasticization);
Impact modifiers (CPE, MBS, or ACR, improving toughness);
Fillers (light calcium carbonate, reducing costs and adjusting rigidity);
Lubricants (internal lubricants such as stearic acid, external lubricants such as paraffin wax);
Pigments/color masterbatches (for colored profiles).
2. Mixing Process
Hot mixing: Heated to 110–120℃ in a high-speed hot mixer (1000–1200 rpm) to ensure uniform dispersion of additives and evaporation of moisture and volatile substances;
Cold mixing: Transferred to a cold mixer to cool down to 40–45℃ to prevent powder agglomeration;
Aging: The mixture is left to stand for 4–8 hours to eliminate static electricity and improve fluidity.
Key control points: Mixing temperature, time, and discharge temperature must be strictly controlled to avoid “over-mixing” (premature plasticization) or “under-mixing” (uneven dispersion).

II. Extrusion Molding

1. Extrusion Machine
Equipment type: Conical twin-screw extruder (mainstream) or parallel twin-screw extruder;
Advantages of conical twin-screw: Low shear, high torque, suitable for heat-sensitive PVC;
Common screw diameters: Φ55/110, Φ65/132, Φ80/156, etc. Temperature Control Zones: Typically 8–12 heating zones are set, with a temperature range of 160–190℃ (adjustable according to the formula);
Exhaust System: Some high-end models are equipped with vacuum exhaust ports to remove moisture and volatile substances.

2. Mold (Die)
The flow channel is customized according to the profile cross-section (such as casement window frames, sliding sashes, sealing strips, etc.);
The material is high-quality alloy steel (such as 38CrMoAlA), which is nitrided for wear and corrosion resistance;
Precise mold adjustment is required during installation to ensure uniform output and no welding marks.

III. Shaping and Cooling

1. Vacuum Shaping Table
After the profile leaves the die, it immediately enters a multi-stage vacuum shaping box;
Through negative pressure adsorption and cooling water spraying, it quickly shapes and controls dimensional accuracy;
The vacuum degree is usually 0.02–0.06 MPa, adjustable in sections;
Equipped with an automatic height adjustment device to adapt to profiles of different heights.

2. Spray Cooling Water Tank
Further uniform cooling to prevent internal stress deformation;
Water temperature is controlled at 10–20℃ to avoid increased brittleness caused by rapid cooling;
The length is generally 6–15 meters, depending on the complexity of the profile and the line speed.

IV. Traction and Cutting

1. Traction Machine
Uses upper and lower crawler-type traction with adjustable clamping force;
The speed is linked to the extruder to maintain constant tension and prevent stretching deformation;
The traction speed is usually 3–8 m/min (depending on the profile specifications).
2. Cutting System
Planetary saw or reciprocating cutting machine for online fixed-length cutting;
Equipped with encoder + PLC control, length accuracy ±1 mm;
Automatic chip collection to keep the site clean.

The PVC profile extrusion line is a highly collaborative system engineering project. From formula design to final packaging, every link affects the product’s performance and market competitiveness. With the deepening of intelligent manufacturing and green manufacturing concepts, modern PVC profile production lines are rapidly developing towards high precision, low energy consumption, reduced manpower, and traceability. Only by simultaneously improving their understanding of processes, equipment selection, and refined management can companies remain invincible in fierce market competition.