Patent ID: 7029623

Claim:
A method for manufacturing a ceramic ball, comprising: a forming step comprising the steps of loading a rubber die with a spherical preliminary green body formed from a ceramic powder and applying pressure to the preliminary green body via the rubber die to thereby obtain a spherical green body of high density; and a firing step for firing the spherical green body; wherein the rubber of the rubber die for accommodating the preliminary green body has a durometer hardness not higher than 65; wherein said forming step is a dry, cold pressing process in which an inner rubber die is accommodated within an outer rubber die, and pressure is indirectly applied to the inner rubber die via the outer rubber die, and wherein the rubber of the inner rubber die has a durometer hardness not higher than 65; and wherein, in said dry, cold pressing process, a radially outer rubber die is disposed in such a manner as to enclose the inner rubber die radially from the outside with respect to an axis passing substantially through a center of the preliminary green body and wherein the inner rubber die is radially compressed via the radially outer rubber die, while the inner rubber die is also axially compressed by axially-pressing means.