(Article reprinted courtesy of our partners at Dalton Electric Heating Company.)
Extrusion machines can be fitted with a variety of dies. A continuous sheet of plastic employs the use of a sheet die, sometimes called a hanger dies, due to the clothes hanger shape of the plastic channel to the extrusion lip of the die. The die must be heated to keep the plastic viscous and this is accomplished by cartridge heaters.
Heaters are installed from the back of the sheet die, extending toward the lip of the die where the plastic is released as a sheet. The Watt-Flex® cartridge heater has several distinct advantages over conventional cartridges. The hot tip feature of the Dalton heater gets more responsive heat to the end of the bore and the lip of the die for greater production control.
And the sheet die generally has a closed bore, sometimes with a small knock-out hole for stuck heater removal. The Watt-Flex heater will expand in the bore for better heat transfer and contract for ease of removal. Better performance and no seized heaters!