Vis - screwsThe Twin Screw Extrusion (TSE) process , developed by Clextral for over 50 years, enables the continuous production of highly homogeneous and finely structured products, using bio-sourced or synthetic raw materials. It is used to produce a wide range of Food & Feed products, Cellulose pulps, Bio-sourced plastics and chemicals.

How does extrusion work?

Extrusion processing aims to physico-chemically transform continuously viscous polymeric media and produce high quality structured products thanks to the accurate control of processing conditions.

Clextral twin screw extruders consist of two intermeshing, co-rotating screws mounted on splined shafts in a closed barrel. Due to a wide range of screw and barrel designs, various screw profiles and process functions can be set up according to process requirements. Hence, a twin screw extruder is able to ensure transporting, compressing, mixing, cooking, shearing, heating, cooling, pumping, shaping, etc. with high level of flexibility. The major advantage of intermeshing co-rotating twin screw extruders is their remarkable mixing capability which confers exceptional characteristics to extruded products and adds significant value to processing units.

In twin screw extrusion processing, the raw materials may be solids (powders, granulates, flours), liquids, slurries, and possibly gases. Extruded products are plastics compounds, chemically modified polymers, textured food and feed products, cellulose pulps, etc.

The advantages of twin screw extrusion

Twin screw extrusion has become the standard over time in several industries because it offers numerous advantages over single screw extrusion:

  • More consistency in production and control of product quality
  • Increased productivity due to continuous processing, faster start up and shut down between product changes, quick changeover and advanced automation
  • Greater flexibility, with the capability to process a wide range of raw materials
  • Optimized footprint thanks to energy and water savings
  • Simple and easy to maintain and clean

Did you know?

There are different types of extrusion processes

Cold extrusion is used to gently mix and shape dough, without direct heating or cooking within the extruder. In food processing, it is used mainly for producing pasta and dough. These products can then be subsequently processed: dried, baked, vacuum-packed, frozen, etc.

Hot extrusion consists of thermomechanically transform raw materials in short time and high temperature conditions under pressure. In food processing, it is used mainly to cook biopolymer-based raw materials to produce textured food and feed products, such as ready-to-eat breakfast cereals, snacks (savory and sweet), pet foods, feed pellets, etc.

Steam-induced expansion, means melt expansion at the die exit due to water flashing off, hence leading to highly expanded products. Subsequent processing then determines the textural attributes of extruded products such as  crispness, crunchiness, hardness, etc. This process is used to produce directly expanded breakfast cereals, snacks and crispy breads.

Expanded co-extrusion combines steam-induced expansion and filling injection, hence leading to expanded products with dual textures. It is mainly used in breakfast cereals and snacks.