The design of a single screw extruder depends on its capacity, purpose and operation (normal and high speed). Small capacity single screw extruders for co-extrusion applications or laboratory testing such as SJ25 or SJ35. Changing the barrel diameter allows the use of larger single screw extruders to handle higher throughputs, such as the SJ65 with a 33:1 L/D ratio, with a maximum throughput of 150 kg/h.
Screw diameter usually affects output, some larger screw extruder models include the SJ90 with a diameter of 90mm or the SJ120 with a maximum output of up to 1000 kg/h. When working with manufacturers, their engineers should recommend the optimal L/D ratio, output capability, and gearbox design adequate for your manufacturing needs.
How does a single screw extruder work? The main process steps using a single screw extruder include:
A1: Feeding via Hopper – Material is gravity fed.
A2: Melting of raw material – this is due to the high temperature inside its single screw barrel. The rotating screw promotes uniform mixing and conveys the melt material through other temperature zones.
A3: Extrusion of molten material – the molten mixture is extruded from the barrel into the die for molding
A4: Calibration – The extrudate is calibrated to the desired size before cooling.
A5: Cooling and Solidification of the Melt – When the extrudate leaves the die, it must cool to maintain its shape. There are different ways to cool hot extrudates, including using air cooling or immersion in cold water. Structure, Design and Working Principle
Single screw extruders are ubiquitous in the plastics manufacturing industry. Some of their uses include:
Production of PE pipes for domestic and irrigation water.
A1: Manufacture of PPR pipes for industrial piping systems, sanitary water pipes, hot water delivery, etc.
A2: Stranding as part of a plastic pipe extrusion line
A3: Co-extrusion application of plastic profiles
A4: Recycling application
A5: Manufacture of HDPE pipes
A6: Production of PP hollow panels and building panels
A7: Recycling granulation
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