Extrusion heads can be categorized into two groups depending on the type of
extrudate obtained and the position of the extrusion head die with regard to the
plasticizing system. The first group includes the extrusion heads for profile (circular and
non-circular), blown film, flat film and sheet, for coating, pelletizing and blow moulding.
The second group includes the longitudinal extrusion heads (straight type) with polymer
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inlet and outlet located on one axis coinciding with the plasticizing system axis, the
angular (skew type) extrusion heads with the polymer inlet on the plasticizing system axis
located at an angle with regard to the polymer outlet axis and the transverse extrusion
heads (cross type) with the polymer inlet and outlet located perpendicularly with regard to
each other. Considering the polymer flow direction with regard to the axis of the extrusion
head main body, the following types of extrusion heads can be distinguished: longitudinal,
angular, transverse and spiral extrusion heads [67]. The spiral extrusion heads can be
made as longitudinal as well as transverse ones. 
Solid or foam polymer extrudates can be obtained in the extrusion process
performed by means of extrusion heads. The extrusion heads for solid polymers and the
extrusion heads for foam polymers can be distinguished since they differ slightly with
regard to their design