Achieving minimal contamination of conductive material during manufacturing proves to be a difficult task. One successful technique is known as levitation melting. This technique produces small quantities of electrically conductive material by suspending and then melting the material with induction heating.
Once the material has melted, the RF power is shut off, and the molten mass can be dropped or forced into a mold for forming. Potential for this application lies in the jewelry, dental, electronics, and aerospace research industries.
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 or parts within precise production tolerances, without disturbing individual metallurgical characteristics.
Solid state RF induction power supplies are ideal candidates for levitation melting. Levitation melting relies on a complex balancing act involving three- dimensional forces. By using solid state equipment, consistent and reliable melting cycles are produced through accurate frequency tuning and power control.
Typical RF power supplies for levitation melting range from 1 to 5 kW, depending on the material and application requirements.
When a conductive material is placed in an induction field, a current is induced which, through resistance, creates heat. While heating is occurring, opposing magnetic flux zones develop that lead to uneven forces acting upon the molten mass. These forces, when controlled properly, can produce an upward motion of the mass.
The first step is to produce a strong magnetic field gradient which is accomplished through the use of a helical conical induction coil (as shown in the video and application note). Next, vertical stability must be achieved by using a reverse direction coil on top of the conical coil, known as a bucking plate. By combining the conical coil with a bucking plate, a "null" zone is created. The levitated metal will migrate to and remain in this zone.
As RF power continues to be applied, the metal melts and the molten mass remains at the levitational point. This molten zone is free from impurities and mechanical interference.