Patent ID: 8057731

Claim:
A process of fabricating a three-dimensional object, said process comprising the following sequential steps of: a) providing a powder layer made of a powder material to have a uniform thickness; b) irradiating a light beam to a selected portion of said powder layer to sinter or melt said selected portion into a cured layer; c) providing an additional powder layer on said cured layer; d) irradiating said light beam to a selected portion of said additional powder layer to form an additional cured layer consolidated with said cured layer; and e) repeating the steps of c) and d) in order to stack said cured layers to provide said three-dimensional object, wherein said cured layer comprises a first cured portion and a second cured portion having a lower density than said first cured portion, wherein a vertically movable elevation stage is utilized to hold said cured layer, said elevation stage being lowered before every step of c) so as to be supplied with said powder material, thereby forming thereon the powder layer of uniform thickness, and wherein said process is further characterized by the following sequential steps of: i) making a primary irradiation of irradiating said light beam to an outline area of at least one of said powder layers forming an outer shell of said three-dimensional object in order to form a primary cured layer as a part of said first cured portion; ii) supplying an extra amount of said powder on top of said primarily cured layer of which thickness is reduced as a result of being cured with the elevation stage kept in the same level as in said step i), so as to provide a supplemental powder layer of a uniform thickness on said primary cured layer; iii) making a secondary irradiation of irradiating said light beam to at least one portion of said supplemental powder layer in order to form a secondary cured layer as a part of said first cured portion, said secondary cured layer consolidated to said primarily cured layer; and iv) irradiating said light beam to a remaining portion of said powder layer confined by said outline area and not converted into said primary cured layer in order to form a low-density cured layer as said second cured portion.