The majority of polymer films are manufactured by film blower extruders (blown film extrusion). Film blowing process: A single screw extruder is used to melt the polymer and force it into a tubular die. Air is blown into the centre of the extrude tube and causes it to expand in the radial direction. Adjustments to wall thickness and diameter are made in this continuous bubble or tube.
Extension of the melt in both the radial and down-stream direction stops at the freeze line (frost line) due to crystallization of the melt. The nip rolls collect the film, as well as sealing the top of the bubble to maintain the air pressure inside. This is used extensively with polyethylene and polypropylene.
The process includes heating & cooling. The heating process eliminates toxic gases, while the cooling process allows for the material to be cut into pellet form, ready for the next stage in the process, plastic manufacturing.
The plastic is then heated & melted in the screw of the extruder before it’s forced through a screen (this screen removes steel, paper and contaminants) to form plastic strands. These ‘spaghetti strands” are cooled in a bath before its pelletised (cut) into small pellets.
Our extrusion lines include the extruder, hopper, control panel, stainless steel water bath and pelletiser.
(Also see our plastic manufacturing product and auxiliary equipment range in the catalogue)
Hume Machinery also sells cooling towers that are used in the process to keep the water cool as well as strand coolers which are used to blow water off the strands before being pelletised as well as assist with the cooling process that the plastic requires.
Our recycling extruders are available from 50kg/hr capacities, 100, 150, 200, 500kgs/hr
It is available in three granulator blade configurations, namely the straight blades, staggered blades and V shape blades. We have also introduced a RS-1000 and RS-1200 Granulator, cutting from 1-2 tons/h.