Although induction heating is normally used with metals or other conductive materials, plastics and other non-conductive materials can often be heated very effectively by using a conductive metal susceptor. The susceptor is used to transfer heat to the target part through conduction or radiation.
Graphite is frequently used as a susceptor because it offers machinability, high resistivity (ideal for induction), and a temperature range up to 3000°C (5430°F). Susceptors can also be made from Molybdenum, Silicon Carbide, Stainless Steel, Niobium, Aluminum, and other conductive materials. The susceptor can be made in the form of a crucible, disk, tube, a layer in the material, or whatever form best suites the application. Some example applications include: crucible melting of non conductive materials like glass, heating fluids in a pipe, plastic sealing, thermoplastic composite manufacture, cap sealing, and CVD processes in semiconductor manufacturing.
Modern induction heating provides reliable, repeatable, non-contact and energy-efficient heat in a minimal amount of time. Solid state systems are capable of heating very small areas within precise production tolerances, without disturbing individual metallurgical characteristics.
When heating a susceptor, solid state RF induction power supplies provide accuracy and speed. During heating, temperature ramping can be controlled by using optical pyrometers or thermocouples to form a closed loop system. Uniform surface temperatures can be achieved with careful coil design.
Typical RF power supplies for susceptor heating range from 1 to 20kW, depending on the parts and application requirements.