Air-cooled blown-film extrusion machines can allow energy loss through convection cooling when the dampers are closed, victims of the so-called 'chimney effect'. A new extruder design removes heat and air currents from the extrusion area, using dampers that are connected to a common air plenum integrated into the machine base, which is in turn connected to a single exhaust fan, either connected to the base or remote mounted. The single central exhaust blower removes the need for more traditional individual blowers on each zone.
With American Kuhne Inc.'s Backdraft extruder, when a damper opens, air is drawn down through the heater's cooling fins and through the exhaust system. The company says this reverse cooling arrangement eliminates the need for exhaust hoods, as well as any potentially damaging air currents near the bubble area....