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Chromalox announces the Maxi-Zone High Temperature Insertion Heater, designed to provide precise, uniform heating of large platens for hot metal presses requiring continuous sheath temperatures to 2000 degrees F. Unlike regular insertion heaters, a Maxi-Zone provides two or three independently controlled temperature zones along the heater sheath. This provides a fine degree of control over hot metal forming processes, enabling increased manufacturing quality. In addition, Maxi-Zone heaters provide efficient radiant heat (not conduction) using sheath diameters smaller than the platen passages. This results in relatively low watt densities and prevents heater sheaths from seizing up in the passages – an important feature, since platens and heaters in metal forming presses are frequently changed. The Maxi-Zone is available in lengths from 8 to 172 inches, and diameters from 0.685 to 0.935 inches, for nominal platen passages from 9/16 to 1-1/4 inches in diameter. A 0.495-inch diameter Maxi-Zone is available for single-zone control.

A uniform platen temperature is critical in the super plastic forming of jet engine fan blades and other titanium parts for the aerospace industry, as well as components for heating and air conditioning equipment. Generally, more heat is required at the edges of these platens than in the center where heat loss is lower. Other applications that benefit from a Maxi-Zone's uniform temperature control include industrial furnaces, aluminum extrusion machines, and ceramic platen presses used for short-run production parts.

Each Maxi-Zone Insertion Heater is constructed of two to six separate resistive heating elements arranged and swaged in place in an Inconel® 600 sheath. Elements are electrically isolated from the sheath wall with a refractory insulation material. Two or three heating zones are staggered along the length of the sheath. When multiple Maxi-Zone heaters are installed, the user can independently monitor and control the heat to each zone, achieving a uniform platen temperature. Inconel sheaths provide durable protection at high temperatures, and as they age, a dark oxide forms on their surface; over time, this improves radiant heat transfer.

Temperature control with a Maxi-Zone heater can be achieved with just about any resistive heating control system. This can be a PID logic controller and SCR power pack, which will provide low hysteresis for tight temperature control. Chromalox supplies a complete line of DIN temperature controllers and SCR power packs for this purpose, including multiple loop controllers with features such as soft-start, ramp and hold, and automated fuzzy logic PID tuning.