The work coil is positioned as close as possible to the bond line, with the work coil normally located 0.020 to 0.030 from the outside perimeter of the part. This distance is referred to as the coupling distance. The strength of the electromagnetic field is inversely proportional to the coupling distance.
If the part geometry does not allow for a minimal coupling distance, the coupling distance may be increased, but will remain uniform to ensure uniform heating at the bond line.