Understanding Screw Zone Functions and Temperature Control in Polyester Chip Spinning

In the melt spinning of polyester chips, the screw extruder is the core component that determines melt quality and spinning stability. Its four functional zones work together to complete chip conveying, melting, homogenization, and the stable delivery of the polymer melt to the spinning assembly. Proper temperature control in each zone directly affects viscosity uniformity, filament strength, and production efficiency.

1. Functional Zones of the Screw

Feed Zone — Stable Conveying

The feed zone receives polyester chips from the hopper and gently preheats them through barrel heating and friction. This prevents bridging and ensures smooth, continuous feeding. Consistent feeding is essential for stable melt pressure in polyester spinning.

Compression Zone — Main Melting Section

As channel depth decreases, chips undergo compression, shear, and heating. Here, polyester chips transition from a solid to a melt, moisture evaporates, and the polymer becomes uniformly fluid. The typical compression ratio for polyester spinning screws is 2.5–3.5, balancing melting efficiency and polymer stability.

Metering Zone — Homogenization and Pressure Stabilization

This zone further mixes the molten polyester and stabilizes the melt pressure. With constant channel depth and mixing elements, it ensures uniform melt viscosity — critical for stable fiber fineness, fewer filament breaks, and smooth spinning performance.

Homogenizing Zone — Final Melt Conditioning

Some screw designs include an additional homogenizing section to eliminate residual temperature fluctuations and prevent degradation. The goal is to deliver a stable, clean, and uniform polymer melt to the spinning pack.

2. Recommended Temperature Settings

Polyester chips typically melt at 255–265°C, so the temperature must increase gradually along the screw.

Suggested Temperature Profile

  • Feed Zone: 220–240°C
    Prevents sticking and ensures smooth conveying.

  • Compression Zone: 250–275°C
    Early melting and final homogenization take place here.

  • Metering Zone: 270–280°C
    Stabilized melt temperature; avoid >285°C to prevent degradation.

  • Homogenizing Zone: 272–282°C
    Target variation: within ±2°C for optimal viscosity control.

Adjustments

  • Chips with higher moisture → increase compression zone by 5–10°C

  • Higher screw speed → increase general temperature by 3–5°C

  • Modified polyester (bright, flame-retardant, CDP, etc.) → adjust based on melting behavior

Common Issues

  • Feed zone too hot → feeding instability

  • Metering zone overheating → gels and yellowing

  • Significant temperature gaps → uneven viscosity, filament breaks

3. Why Proper Screw Control Matters

A well-designed screw temperature profile ensures:

  • Efficient melting of polyester chips

  • Uniform melt viscosity

  • Lower degradation and gel formation

  • Better spinning stability and higher fiber quality

  • Longer equipment life and reduced maintenance

For manufacturers of polyester fiber, filament yarn, industrial yarn, and specialty polyester materials, optimizing screw zone operation is one of the most cost-effective ways to enhance production stability and product performance.