Research On Visualization And Toolpath Planning Of Functionally Graded Material Parts

Functionally graded material is different from homogeneous materials and composites, which is accomplished by introducing a compositionally graded layer between the comprising materials so that the material parameters can vary continuously. However, the drawbacks of chemistry or physics based methods are as follows.Firstly, only material block, blank and rings with simple shape can be fabricated.Secondly, OEC cannot be fabricated by conversional way.Finally, material primitives cannot be controlled precisely, which may not meet the designer's intention.Fortunately, Rapid prototyping(RP) technology, also called solid freeform fabrication(SFF)or layered manufacturing(LM), possesses the capability to fabricate FGM with complex structure as the characteristic of additive material drop by drop and layer by layer.However, current CAD modeling systems providing 2D slicing data for RP machine is incapable of modeling FGM part, much less offering slicing files with material information. In this thesis, under the circumstances of rapid prototyping technology the problem of material representation in complex part is studied theoretically and experimentally. A visualization, slicing and tool-path planning system is designed and developed, which makes it possible to manufacture FGM by RP technology.The main contents about this thesis are summarized as follows.1. On the basis of analysis of errors and disfigurements of STL(StereoLithography), a diagnosis and repairing algorithm is presented through constructing a non-redundant data structure. For the problem of low precision of some STL model, an adaptive subdivision surfaces algorithm is proposed based on the Loop and half-edge ratio to improve the smoothness of the surface while maintaining the shape features of a model, so that we can use less data to represent more accurate STL model.2. Algorithm of voxelization of CAD mesh model are studied systematically. A voxelizatin algorithm on the basis of Quard-tree and Ray-Casting algorithm is proposed. Analysis the method of distance calculation based on digital distance transform.3. It is studied deeply of the FGM modeling theory in terms of voxel-based representation of a CAD part.A FGM modeling algorithm on the basis of the definition of distance filed is presented,which overcomes the drawback of being incapable of evaluating material in negative constant material area. A slicing algorithm based on the material information is proposed. A material resample algorithm between neighboor material slices and in a single slice is proposed based on the geometric slicing constraints,4. Based on above algorithm, a tool-path planning method with graded material based on material isoline is proposed.