Dexel-based direct slicing of multi-material assemblies

Slicing is an important procedure in rapid prototyping (RP) pre-processing, and can be grouped into two categories: direct slicing and adaptive slicing. At present, investigations into the use of both direct and adaptive slicing methods are taking place. However, not many direct slicing approaches have been reported in the literature. The methods are also restricted to some solids in CSG or some CAD systems. Also, approaches on adaptive slicing are too complicated. The method proposed in this paper employs dexel encoding for direct slicing multi-material (MM) assemblies in RP. One advantage of using a dexel model is that Boolean operations can be performed simply on 1D line segments. Dexels can also be easily converted to tool paths in RP machines. Compared to the ray representation of CSG trees, dexel models can be extended to represent MM assemblies with material properties. Therefore, the method has high potential for direct slicing. In this paper, traditional dexel models are first extended for rapid manufacturing single solid and MM assemblies. Compared to other adaptive slicing approaches, a much more efficient and simple dexel model, for adaptive refinement in the building direction is then developed. To further improve the surface finish, a layerwise refinement approach is also discussed. Finally, the computational complexity of the proposed method is studied.