Fish Products and Byproducts Technology

Unit 6 - Extrusion

6.6. Types of extruders
There are three major types of extruders.

• Piston extruders
• Roller extruders
• Screw extruders

Piston extruder: can consist of single piston or multiple sets of pistons that deposit a process amount of product on to conveyers or trays. Piston extruders are primarily used for forming product shape and are used in confectionary as well as bakery production facilities.
Roller type extruder: are used to form the shape of a product. A roller consis of two counter rotating roller that either turn at similar or differential speeds. This process is also referred as calendaring in that dough industry. The roller surfaces can be smooth to create a long thin strip or can be perforated to form the dough in to shaped products.
Screw extruders: Utilize single, twin or multiple screws rotating within a metal cabinet called the barrel. The screws convey the material formed and though a small orifice called die which can take on many shapes and sizes. Several external parameters such as screw speed and configurations, temperature of the barrel, die size and shape and the length of the barrel effect the properties of the final product.