Orientation Optimization Algorithm In The Ideal Material For Parts Digital Manufacturing

Ideal Functional Material Components (IFMC) is an heterogeneous object which is designed to achieve the best use function, and constructed by composition materials, period functional meso-structure (PMS), functional gradient materials (FGM) and homogeneous materials. IFMC can meet the service functional and intelligent demands of high technology, and thus, researches on designing and manufacturing of IFMC are having been a hot spot in recent years. The heterogeneous characteristic of IFMC calls for the Digital Concurrent Designing and Manufacturing (DCDM) technology. Rapid Prototyping Manufacturing (RPM) technology, one of the foundational technologies of DCDM, is an emerging technology for creating physical prototypes from CAD models layer by layer. The additive/ subtractive characteristic of RPM just meets the requirement of DCDM for IFMC, so RPM technology is one of the most feasible methods for manufacturing IFMC until now.Since the process of RPM is bottom-to-up building process, very like the growth of a plant, it is necessary to select a surface of the component as bottom before the component is built, namely, to fulfill orientation for the component model. Orientation is very important for most RPM technologies as it affects the surface finish of component, efficiency, cost, and reliability of component process. As for IFMC, apart from factors mentioned above, different orientation will have different material error. Although there is no orientation on which all the above factors can be optimized, it is possible to choose the most important one or several factors as optimization objective to determine a comparatively optimal build orientation. Because of the non-homogeneous material characteristic of IFMC, the algorithms of orientation optimization for conventional homogeneous part are not suitable for IFMC. After researching the features of IFMC, based on the optimization algorithms for conventional homogeneous part, a new algorithm of orientation optimization for IFMC is presented in this paper. In order to find the build orientation for IFMC, an optimization equation with the multi-objective of minimum slice number and maximum bottom surface area is established, under the restriction of the stability and the given stair-step error. Then, an algorithm without limitation to any particular RPM technique to solve the equation is presented.Considering the heterogeneous material characteristic of IFMC, a new data format based on simple subdivision of model with tetrahedron, instead of STL format, is applied simultaneously to describe geometry, topology and material information 'of the component. So as to realize automatization of data processing and unification of data format during the whole RPM process of IFMC. Moreover, a method of calculating gravity center coordinate of IFMC is also proposed, which is one of the important content in the algorithm of orientation optimization and, is used to determine whether the component is stable or not in this orientation.A system software module is developed with VC++ on Windows 2000 platform, it has the functions as following: displaying, moving, rotating, enlarging and reducing of 3D CAD model, and automatic orientating of IFMC based on adaptive slicing technology.