The type of localized, interior heating produced by cartridge heaters is used to heat specific parts of machinery used in packaging, die cutting, mold forming, hot stamping, labeling, sealing, printing, fluid heating, food service and many other industries. Hot plates, platens, semiconductors, shrink wrap machines and labeling machinery often use internal cartridge heaters to heat specific applicator parts. Plastic and rubber forming processes in particular make extensive use of cartridge heaters and other localized heating systems like strip heaters to assist in the plasticization of materials. Cartridge heaters are available in a wide variety of configurations and compositions to suit the equally wide variety of contexts in which they are applied.
Assembled with similar materials to other types of electric heaters, cartridge heaters are commonly formed from electric coils insulated by ceramic material and encased in a metal sheaths. Insulating materials may also be mica, mineral or fiberglass, depending on the desired wattage and application for the heater. Insulation is necessary between the heating coil and the sheath because contact between the two materials can cause short-circuiting. Sheaths can be constructed from a variety of materials including aluminum, copper, iron, nickel and stainless steel.
Some cartridge heater configurations are folded in half, allowing the cartridge to expand as it heats, making contact with the material surrounding it on all sides, thereby providing more effective and evenly distributed heat. Engineers and designers must be extremely precise when using cartridge heaters in equipment, making sure to install cartridge heaters with the proper wattage, heat temperature and oxidation effects in relation to the material in which it will be immersed.