Extruder

An extruder works by moving the material through a rotating screw in a cylindrical barrel. The material passes through several steps:

Process steps of an extruder

• Feeding: the raw material, e.g. plastic granules or rubber compound, is fed in via a hopper.

• Conveying and plasticising: the material is moved by the rotating screw, heated and plasticised.

• Homogenisation: shear forces and pressure mix the material evenly.

• Shaping: the molten material is pressed through a forming die, which creates the desired cross-sectional shape.

• Cooling and finishing: after leaving the die, the material is cooled and processed further if necessary (e.g. cutting or winding).

Component	Function
Hopper	Feeds the raw material into the screw.
Screw	Conveys, heats and homogenises the material.
Barrel	Contains the screw and enables plasticising by heating.
Heating and cooling system	Regulates the temperature in the barrel to control the material properties.
Forming die	Gives the material the desired shape.
Drive unit	Drives the screw and controls the speed.

There are various types of extruders, which differ in their design and intended use:

Type	Description	Typical applications
Single-screw extruder	Has a single screw and is the most common design.	Profiles, films, pipes
Twin-screw extruder	Has two intermeshing screws for better homogenisation.	Compounding, mixing colours and additives
Planetary roller extruder	Enables particularly high homogeneity and precise temperature control.	Thermoplastic elastomers, sensitive materials
Laboratory extruder	Smaller extruders for research and development purposes.	Material tests, prototypes

• Efficiency: continuous production enables high output rates.

• Versatility: suitable for different materials and shapes.

• Precision: enables the production of products with consistent quality and exact dimensions.

• Cost efficiency: optimises material consumption and lowers production costs.

Plastics industry

• Production of pipes, profiles and films.

• Cable sheathing and packaging materials.

Rubber industry

• Production of hoses, profiles and round cords.

• Processing of thermoplastic elastomers (TPE).

• Temperature control: precise control is crucial to avoid damage to the material.

• Material wear: screws and barrels can wear due to abrasive materials.

• Energy consumption: operating an extruder requires a considerable amount of energy.

Feature	Single-screw extruder	Twin-screw extruder
Design	One screw	Two intermeshing screws
Homogenisation	Medium	Very good
Typical materials	Standard plastics	Mixed materials, compounds
Costs	Lower	Higher
Applications	Profiles, pipes	Colour mixing, additive compounding

• Which materials can be processed in an extruder? Extruders can process plastics, elastomers (rubber) and thermoplastic elastomers (TPE).

• What are typical problems with extruders? Common problems are material blockages, uneven conveying and wear of screws and barrels.

• How is the quality of an extrudate ensured? Through precise temperature control, the right screw configuration and regular maintenance of the machine.

• Which types of extruder are suitable for demanding applications? Twin-screw and planetary roller extruders offer particularly high precision and homogeneity for complex materials.

The extruder is an indispensable tool in the plastics and rubber industries. With its ability to shape materials continuously and precisely, it enables the manufacture of high-quality products for numerous applications. Whether in plastics production or the rubber industry, extruders offer efficiency, versatility and precision.