Plastic extruders are basically screw extruders applied in the plastic industry for melting mixing and preparing the plastic material for extrusion. The profiles that can be made through this plastic extruders has a wide range that includes films, enclosed tubes/ bags in fact any shape in a continuous manner. A schematic of a basic extruder machine is shown here.


In the extruder machine, plastic pellets or beads popularly called as resins are fed from a hopper along the feed screw via a barrel chamber. As the resin makes its way along the barrel, it is subject to many forces in the form of compression, friction and heated zones. This makes the resin to melt. As it further travels the exit end of the screw helps to mix the melt in a homogeneous manner. The melt then enters a chamber that is designed for securing an evenly distributed flow to the die. In some machines, there is a melt pump in place to prevent occurrence of any pressure surges.

For co-extruding sheet products more than two plastic extruders are used. This facilitates multi-layer structures with distinct layers of plastic polymers. Plastic extruders are quite capable of making a vast range of items, these include tubes, sheets, rods, channels, and other custom shapes.

Types of Plastic Extruders

There are two types of extruders that are used for extruding of the plastics. They can be broadly classified as :

• Single Screw Extruder
  Single screw extrusion is one of the primary operations in the processing of polymers. The basic aim of a a single screw extruder is to build sufficient pressure in a polymer melt for it to be extruded through a die. A single screw Plastic Extruder is known to be having a more severe effect in handling of plastics. This may result in more degradation as compared to twin screw machine. A diagram is given here of a very simple Single screw extruder machine.
  
  
  Single screw extruders are designed to meet some of the toughest extrusion requirements. Some of them includes:
  • Sheet
  • Window Profile
  • Pipe
  • Tubing
  • Structural foam molding
  • Blow Molding
  • Blown Film
  • Cast Film
  • Wire & Cable
  • Foam Extrusion
  • Fiber Extrusion
  
  
  
• Twin Screw Extruder
  Twin screw extruders are used extensively for variety of applications that ranges from mixing, compounding, or reacting of plastic materials. The basic advantage of a twin screw extruder is its flexibility. Which allows operations to be designed specifically for the formulations under considerations. For example, it s possible that the two screws may corotate, counterrotate, intermesh or there may also be case of non-intermeshing. Additionally, the configurations of the screws can also be altered for getting particular mixing characteristics.

Twin vs Single Screw Extruder

Twin Screw Extruder Twin screw extruders are classic machines that is used in case of compound production. Which means, when two or more ingredients get mixed and extruded for producing a pellet. Single screw extruders prove useful machines in production process, when pure polymer like HDPE is used.

Single Screw Extruder Single screw Extruder produces plastic, wood or other profiles from regrinding chips bereft of the need for pre pelletizing. Twin screw extruders prove useful in case of production of rigid PVC and wood fiber blends.