Injection molding has gained an important role in contemporary manufacturing processes as the use of plastic products has expanded in daily life. In Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) of moldings, the determination of parting curves is critical with regard to the overall structure and the cost of the mold. This thesis proposes three algorithms to automate the generation of parting curves for both conventional two-piece molds and multi-piece molds of complex parts in CAD drawings. In this research, the parting curves can be generated from surfaces of molded parts represented either by a triangular mesh or a non-uniform rational basis spline (NURBS). For surface parts represented by triangular meshes, a multiple-slicing algorithm that uses three sets of cutting planes to slice the 3D model is developed. In the algorithm, one set of cutting planes is used to generate the slicing profiles, and two others are used to determine the intersection points through which the inner and outer loops of the parting curves pass. For the case where the surfaces of a part are represented in NURBS form, a hybrid algorithm is utilized. Based on the geometric properties of specific entities, different sets of visible-moldable surfaces for mold-pieces and undercut features are identified. The parting curves are generated based on the combination of both outermost boundary edges and the visible silhouette segments of the relevant surfaces.
For complex parts that require the use of multi-piece molds, a collection of feasible parting directions is formed, from which sets of visible-moldable surfaces for each parting direction are also determined. Then, a mold-piece region algorithm (MPR) is applied to arrange surfaces of molded parts into appropriate regions for mold-pieces. Based on this, the parting curves corresponding to each mold-piece can be extracted.
The three proposed algorithms achieve the goal of high accuracy and high performance, and can also be applied to other current CAD/CAM systems and applications in industrial mold design.

Injection molding has gained an important role in contemporary manufacturing processes as the use of plastic products has expanded in daily life. In Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) of moldings, the determination of parting curves is critical with regard to the overall structure and the cost of the mold. This thesis proposes three algorithms to automate the generation of parting curves for both conventional two-piece molds and multi-piece molds of complex parts in CAD drawings. In this research, the parting curves can be generated from surfaces of molded parts represented either by a triangular mesh or a non-uniform rational basis spline (NURBS). For surface parts represented by triangular meshes, a multiple-slicing algorithm that uses three sets of cutting planes to slice the 3D model is developed. In the algorithm, one set of cutting planes is used to generate the slicing profiles, and two others are used to determine the intersection points through which the inner and outer loops of the parting curves pass. For the case where the surfaces of a part are represented in NURBS form, a hybrid algorithm is utilized. Based on the geometric properties of specific entities, different sets of visible-moldable surfaces for mold-pieces and undercut features are identified. The parting curves are generated based on the combination of both outermost boundary edges and the visible silhouette segments of the relevant surfaces.
For complex parts that require the use of multi-piece molds, a collection of feasible parting directions is formed, from which sets of visible-moldable surfaces for each parting direction are also determined. Then, a mold-piece region algorithm (MPR) is applied to arrange surfaces of molded parts into appropriate regions for mold-pieces. Based on this, the parting curves corresponding to each mold-piece can be extracted.
The three proposed algorithms achieve the goal of high accuracy and high performance, and can also be applied to other current CAD/CAM systems and applications in industrial mold design.

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