Induction Welding Process

induction welding heating process

Induction welding, also called electromagnetic or EMA welding, uses induction heating from radio frequency (typically 2 – 10 MHz) alternating current to magnetically excite an implant placed at the joint interface of the two parts being welded. This implant, or gasket, is normally a composite of the polymer to be welded with either metal fi bers or ferromagnetic particles. The heat generated melts and fuses the implant with the surrounding material. It is a reliable and rapid technique, ranging from fractions of a second for small parts to 30 – 60 seconds for parts with long (400 cm; 157 inches) joint lines, and results in structural, hermetic, or high-pressure welds [1, 2] . The two most commonly encountered mechanisms by which heat can be generated by an induction fi eld are eddy current heating and heating due to hysteresis losses. In eddy current heating, a copper induction coil (work coil), which is connected to a high-frequency power supply, is placed in close proximity to the joint ( Fig. 11.1 ). As electric current at a high frequency passes through the work coil, a dynamic magnetic fi eld is generated whose fl ux links the implant. Electric currents are induced in the implant, and when these are suffi ciently high to heat the conducting material, the surrounding thermoplastic parts soften and melt. If pressure is applied to the joint, this aids wetting of the molten thermoplastics, and a weld forms as the joint cools [3, 4] .

induction welding process