A method of additive manufacturing for producing a 2-part mold suitable for use in injection molding, the method comprising: (i) obtaining a computerized 3D representation of a 2-part 3D mold; (ii) automatically delimiting at least two regions within the 3D mold, wherein said automatically delimiting at least two regions within the 3D mold comprises: defining a functional region by: a) generating a convex hull of the closed 3D mold; b) subtracting the original 3D mold structure from the convex hull to obtain a representation of the internal volumes of the closed 3D mold; c) selecting the dominant volume of said internal volumes; d) algorithmically offsetting surfaces of the dominant volume into a solid part of the 3D mold; e) intersecting the offset region with the original 3D mold; and f) defining the resulting region as a functional region; and defining a non-functional region by: a) subtracting the functional region from the original 3D mold; and b) defining the resulting region as a non-functional region; (iii) algorithmically assigning a material or a combination of materials to each delimited region; and (iv) producing said 2-part mold by additive manufacturing including providing said assigned materials or combinations of materials into said delimited regions. (i) obtaining a computerized 3D representation of a 2-part 3D mold; (ii) automatically delimiting at least two regions within the 3D mold, wherein said automatically delimiting at least two regions within the 3D mold comprises: defining a functional region by: a) generating a convex hull of the closed 3D mold; b) subtracting the original 3D mold structure from the convex hull to obtain a representation of the internal volumes of the closed 3D mold; c) selecting the dominant volume of said internal volumes; d) algorithmically offsetting surfaces of the dominant volume into a solid part of the 3D mold; e) intersecting the offset region with the original 3D mold; and f) defining the resulting region as a functional region; and defining a non-functional region by: a) subtracting the functional region from the original 3D mold; and b) defining the resulting region as a non-functional region; defining a functional region by: a) generating a convex hull of the closed 3D mold; b) subtracting the original 3D mold structure from the convex hull to obtain a representation of the internal volumes of the closed 3D mold; c) selecting the dominant volume of said internal volumes; d) algorithmically offsetting surfaces of the dominant volume into a solid part of the 3D mold; e) intersecting the offset region with the original 3D mold; and f) defining the resulting region as a functional region; and a) generating a convex hull of the closed 3D mold; b) subtracting the original 3D mold structure from the convex hull to obtain a representation of the internal volumes of the closed 3D mold; c) selecting the dominant volume of said internal volumes; d) algorithmically offsetting surfaces of the dominant volume into a solid part of the 3D mold; e) intersecting the offset region with the original 3D mold; and f) defining the resulting region as a functional region; and defining a non-functional region by: a) subtracting the functional region from the original 3D mold; and b) defining the resulting region as a non-functional region; a) subtracting the functional region from the original 3D mold; and b) defining the resulting region as a non-functional region; (iii) algorithmically assigning a material or a combination of materials to each delimited region; and (iv) producing said 2-part mold by additive manufacturing including providing said assigned materials or combinations of materials into said delimited regions.