New Backdraft extruder from American Kuhne, Ashaway, R.I., has a reverse-air cooling system suited especially to blown film that removes heat and undesireable air currents from the extrusion area for optimum bubble stability while also improving energy efficiency. When individual dampers are closed, they prevent the “chimney effect” present in most air-cooled machines that allows energy losses through convection cooling.
The dampers are connected to a common air plenum in the machine base, which is in turn connected to a single exhaust fan, either connected to the base or mounted remotely. The central exhaust blower replaces individual blowers on each zone. When a damper opens, air is drawn down through the heater’s cooling fins and through the exhaust system.