Screw

The screw consists of several functional zones, each of which performs specific tasks:

1. Feed zone

• Function: transporting the material from the hopper into the machine.

• Characteristics: large pitch and low compression to convey the material.

2. Compression zone

• Function: compacting and mixing the material.

• Characteristics: decreasing pitch to increase the pressure.

3. Metering zone

• Function: even conveying and metering of the material.

• Characteristics: constant pitch for homogeneous output.

Materials

• Typical materials: high-strength steels, coated or nitrided to resist abrasion and corrosion.

• Surface treatment: plasma coating or hard chrome for a longer service life.

The screw moves and processes material through a combination of rotation and pressure. Its main functions are:

• Conveying: the material is transported from the hopper towards the die or mould opening.

• Mixing: the helical movement distributes fillers, additives and other components evenly.

• Melting: thermoplastics or elastomers are melted by friction and external heating elements.

• Metering: the material is pressed into the mould or extrusion head in even quantities.

Screws are divided into different types depending on the application and material:

Screw type	Properties	Typical applications
Single screw	Simple design, suitable for homogeneous materials	Extrusion of pipes, profiles, films
Twin screw	Better mixing, also for sensitive materials	Compounding, food processing
Barrier screw	Separates solid and molten phases for efficient melting	High-performance extrusion, thermoplastics
Mixing screw	Specifically for intensive homogenisation	Injection moulding, material preparation

Screws are indispensable in a wide range of industries:

Rubber and plastics industry

• Extrusion: production of hoses, pipes and films.

• Injection moulding: production of complex components by precise injection of material.

• Compounding: mixing polymers with additives and fillers.

Food industry

• Conveying: transporting bulk goods such as flour or sugar.

• Shaping: production of pasta or snacks by extrusion.

Chemical industry

• Reactors: processing and mixing chemical raw materials.

• Granulation: production of plastic granules.

The screw offers numerous advantages that make it an indispensable component in industry:

• Efficient conveying: ensures an even material flow.

• Homogeneous mixing: even distribution of additives and fillers.

• Versatility: adaptable to different materials and applications.

• Compact design: combines several functions such as conveying, mixing and melting.

Using screws also involves some challenges:

• Wear: heavy abrasion from abrasive materials can shorten service life.

• Material sticking: sticky or heat-sensitive materials require special coatings.

• Heat generation: excessive friction can cause the temperature to rise uncontrollably.

• Which materials are used for screws? Screws are usually made of high-strength, wear-resistant steels, which are often coated.

• How is a screw maintained? Regular cleaning, checks for abrasion and calibration of the machine are essential.

• Can screws be used for different materials? Yes, by adapting the design and the surface coating they can be used for many purposes.

• What is the difference between a single screw and a twin screw? Twin screws offer better mixing and processing of complex materials, while single screws are simpler and more cost-effective.

The screw is an indispensable component in the rubber and plastics industry. It performs essential functions such as conveying, mixing and melting materials and ensures even processing. Its versatility and adaptability make it a key component in numerous production processes.