The conventional circle coil makes the inductive current flow in a circular direction, therefore, the bottom side cannot be sufficiently hardened to avoid overheating of the top side.
And general line coils have to use electromagnetic cores to ensure the hardened depth on the bottom side.
In this case, the core is heated or gradually deteriorated during the scan hardening, which results in an uneven hardened layer compared with the starting and finishing points.
The 2-turn line coil and 3-bridged coil we developed overcome these disadvantages with the conventional circle coil. Moreover,the 3-bridged coil can minimize the temperature difference between the top and bottom sides.
This allows for high power heating and is best for the hardening of large diameter ball screws.