Screw extruder: Detailed explanation of the core equipment of rubber processing

1. Function and classification of screw extruder

Screw extruder is a key automatic feeding equipment in the rubber industry, mainly used to produce various rubber semi-finished and finished products. According to the different feeding methods, it can be divided into two categories:

Cold feed screw extruder

Features: Directly feed room temperature rubber compound

Advantages: Eliminate the preheating process and save energy by 20-30%

Typical applications: automotive sealing strips, rubber pipes, wires and cables coating

Hot feed screw extruder

Features: Feed the rubber compound preheated by the open rubber mixer (60-80℃)

Advantages: High output, suitable for high viscosity rubber compound

Typical applications: tire treads, rubber tracks, large industrial products

Industry data: In the production of rubber products, about 65% of extrusion operations use cold feed models, and 35% use hot feed models

2. Working principle of screw extruder

The screw extruder completes rubber processing through a three-stage process of mechanical conveying → plasticizing and mixing → pressurized extrusion:

Feeding section (accounting for 30% of the screw length)

Cold feeding model: adopt deep screw groove design (h/D=0.25-0.3) to enhance the material gripping ability

Hot feeding model: shallow screw groove design (h/D=0.15-0.2) to improve the conveying efficiency

Compression plasticizing section (accounting for 50%)

Temperature control:

Cold feeding: 90-120℃ (heating by barrel + shearing)

Hot feeding: 100-130℃ (maintaining pre-plasticized state)

Special design:

Pin type mixing section (dispersion efficiency increased by 40%)

Barrier type screw (output increased by 15-20%)

Extrusion molding section (accounting for 20%)

Die head pressure: usually 5-15MPa (high hardness rubber can reach 25MPa)

Die design:

Expansion rate compensation (rubber extrusion expansion rate is about 30-80%)

Flow channel convergence angle (15-30° to optimize flow)

3. Comparison of technical advantages

Special advantages:

• Cold feed models can achieve co-extrusion of colored rubber compounds (such as two-color sealing strips)
• Hot feed models are more suitable for highly filled formulas (such as rubber compounds containing 50% carbon black)

4. Solutions to common problems