This is most commonly made by forming a length of square or rectangular steel bar into a circle. Welding is done at the ends together. After which various operations happen to complete it. Immediately normalizing is done to remove stresses and improve the properties in the weld area. Turning and generating the teeth by gear hobbing is done followed by heat-treatment operations. The last operation before the welding of the ring gear is to magnetize the rotor magnets.
The strength and wear of the ring gear are increased due to the hardening of it. But the body of the ring is untreated to give ductility and this is done because to weld it to the flexplate and also for shrinking onto the rotor body.