Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section.
The Extrusion Line begins with the hopper which loads the plastic material.
This screw transports the polymer to the die head and simultaneously the material is heated, mixed and pressurized.
The polymer takes up the shape of the mold and is then cooled to give the final shape.
As the polymer cools it is drawn along by haul-off devices and cut to length.
Basic extrusion tooling typically consists of a flat plate die or a round steel plate with a cut opening to the profile shape
These are cut metal blocks which completely encapsulate the profile, while a vacuum pulls the hot shape out against it’s walls as it cools. The cooling medium may be either air or water. This “freezes” the profile in the correct shape. Vacuum sizers are used primarily with hollow shapes.
Molten extrudate is sucked towards the wall of the mold due to the vacuum pressure. Once in contact with the walls, the plastic cools down and takes the final shape of the tube.
Progressive effect of a vacuum sizer
The Haul-Off unit or Puller machine is responsible for drawing the rigid extrudate out from the vacuum sizer and into the cutting machine.
The Cutting Machine is used to continuously cut the tube in the desired length.