US Patent 7099112 Balance ring

An apparatus and method for balancing a disk are described. A balance ring may be a circular band for placement along the inner diameter of a disk. On the outer diameter of the balance ring, one or more clamp structures may extend outward to attach the balance ring to the inner diameter of a disk. The inner diameter of the balance ring may have a number of protuberances that, when trimmed, establish a new rotational center of the disk/balance ring coincident with the mass center. The disk and balancing ring may be mounted on a disk balancing system to determine a mass center and trim the protuberances, accordingly, to establish adjust the rotational center of the disk/balance ring to be coincident with the mass center. The protuberances may be trimmed using, for example, laser energy.