US Patent 8057731 Process of fabricating three-dimensional object

A light beam is irradiated to sinter powder layers into a plurality of cured layer which are superimposed to each other to fabricate a three-dimensional object. A portion forming an outer shell of the object is given by high-density cured layers, while the other portion is given by low-density cured layers. The high-density cured layer making up at least a side of the object is composed of a high-density primary cured layer obtained by irradiation of a primary irradiation to the powder layer, and a high-density secondary layer obtained by a secondary irradiation to a supplemental powder layer supplied on the high-density primary cured layer. Thus, the high-density cured layer is given a height in level with the low-density cured layer, which assures constant height of each cured layer which is a combination of the high-density cured layer and the low-density cured layer.