Process Planning for Additive/subtractive Solid Freeform Fabrication Using Medial Axis Transform

Additive/Subtractive Solid Freeform Fabrication (SFF) integrates material addition (deposition) and removal (machining) to build up three-dimensional objects incrementally. This class of processes offers sophisticated design flexibility with engineering materials, three-dimensional layer building, and the ability to fabricate complex engineering devices and multi-material objects. However, planning for such processes exhibits rigorous challenges due to process flexibility and highly demanding planning automation. These challenges, moreover, can not be sufficiently tackled via common boundary representation of geometric models. In this thesis, various techniques based on the Medial Axis Transform (MAT) are presented. The medial axis transform encodes intrinsic shape characteristics into a lower dimensional metric. The MAT together with the boundary representation empowers shape manipulation and geometric reasoning. Although numerous algorithms have been proposed to recognize the MAT of polygonal objects, a robust model for arbitrarily shaped regions, especially suitable for engineering designs, is still an art of research. The approaches presented in this thesis utilize representation of the MAT in terms of clearance functions on the object boundary. The clearance functions are computed via a divide-and-conquer methodology. Three process planning problems are tackled based on the proposed MAT representation. First, an important task in planning additive/subtractive SFF is to determine whether a computed decomposition plan is feasible for manufacturing. Although decomposed layers may represent valid and manufacturable geometry, the presence of previously built layers may pose manufacturing difficulty. An approach is proposed based on the 2D MAT to assist in detecting such problems. In addition,