The Servtek TCS (Thermal Control Solution) radiant barrel heating/cooling system, developed by Rex Materials Group, Fowlerville, Mich., and distributed exclusively for plastics by Cincinnati Milacron in Batavia, Ohio, is said to bring energy savings of 30% to 50%, to both extrusion and injection molding. In extrusion, it reportedly offers some added benefits due to its unusually efficient air cooling. The radiant heaters don't contact the extruder barrel directly, but are embedded in an insulating shall that is supported by little built-in feet, leaving a 3/8-in. air gap above the barrel. Cooling air is sucked (not blown) at very high speed along the barrel through this gap, divided into separate zones, making this the most efficient form of air cooling on the market, Milacron says.

The heating element is nickel-chromium wire embedded in low-density ceramic insulation, which holds the heat in (unlike conventional heater bands), so the outside of the insulating shell remains cool to the touch. Rex has installed radiant heaters on nearly 30 single-screw extruders of 3.5 to 6 in. diam. over the past four years. Most applications are in sheet, but some are in blown film and pipe. Energy savings are most dramatic for extruders that run 24/7, with added efficiency benefits from converting oil- or water-cooled barrels to high-speed air-cooling. Servtek heaters are being developed for heat- and shear-sensitive materials like PVC and for twin-screw extruders.