Process Planning for Shape Deposition Manufacturing

Solid Freeform Fabrication (SFF) refers to a class of rapid manufacturing process that builds parts by incremental material deposition and fusion of thin 2-1/2 dimensional layers. Over this past decade, SFF has taken the manufacturing industry to new heights. However, parts produced by SFF processes exhibit a stair-step surface texture due to the presence of 2-1/2 dimensional layers and exhibit limited material properties. These issues are addressed by a modified SFF process called Shape Deposition Manufacturing. Shape Deposition Manufacturing (SDM) is a novel layered manufacturing process in which multi-material structures with embedded components can be fabricated. In SDM, the layers are truly three dimensional in nature and are built using a combination of material addition and material removal processes. The need for an automated and robust process planner is more in the case of SDM as it attempts to build fully functional parts directly from CAD models. This thesis focuses on the process planning issues in Shape Deposition Manufacturing. The major issues in process planning for SDM involves the generation of 3-D layers and generation of deposition and CNC cutter paths for these 3-D layers. In SDM, the CAD model is decomposed into 3-D layers of varying thickness based upon both geometric and material criteria. The layers are further decomposed into manufacturable volumes called compacts. Silhouette edges and silhouette loops are identified to help the decomposition of models into 3-D layers and compacts. Unlike techniques used in existing SFF methods which divide models into equally spaced slices, the present algorithm decomposes models into compacts which are