A plastic extruder consists of four parts: a gravity-fed hopper, a drive screw, a die system and a cooling bath. Let us see how does the plastic sheet extruding works.
 
  The plastic begins the extrusion process as granulated pellets. The pellets are added to the gravity-fed hopper at the front of the extrusion machine. More than one type of plastic can be added to the hopper, or other products such as pigments or plasticizers can be added to the base plastic to affect the final extruded part. plastic sheet extruder the of die assembly consists  of a screen to filter out any solids from the liquid plastic, a breaker plate to remove rotational effects from the plastic mixture and provide back pressure and the die itself. The pressure created by the drive screw forces the plastic through the die at a specified rate. For hollow cross sections, the die includes a pin to create the center portion of the shape, which is then pressurized with air to maintain the cross section during cooling.