Research And Development Of Data Processing And Device Driven System For Rapid Prototyping Based On MDT

As a kind of rising integrated technologies, Rapid Prototyping (RP) technology is rapidly developing with the development of various enabling technologies, such as Computer Aided Design (CAD) and Numerical Control (NC) etc. Nowadays, nearly all types of rapid prototyping systems commonly adopt STL file as their data exchange interface. The STL file is a triangularization representation of CAD model surface. Using it to represent CAD model will reduce the part precision. The existing RP-related software include a CAD module, a data processing module, and a monitoring and controlling module, which are independent of one another. Thus, the preprocessing procedure of RP is rather complicated. Aiming at the issues above, this thesis deals with the direct and adaptive slicing methods of CAD model, and develops the data processing and device driven system based on the Mechanical Desktop (MDT) software. The work of this thesis lays a solid foundation for the integration of CAD, CAPP and RP. The main work may be summarized as follows:(1)After discussing all kinds of existing algorithms, this thesis presents a new kind of adaptive slicing algorithm that determines the slicing thickness by comprehensively considering the surface normal and the cross-sectional area. And for the same part, a comparison between the adaptive slicing and the equal-thickness slicing methods is performed. The results show that the adaptive slicing method can greatly improve the manufacturing efficiency in the equivalent precision. The adaptive slicing gains advantage over the equal-thickness slicing.(2)Based on a close research of the interior representation of CAD model in MDT, this thesis picks-up the interior topological and geometrical information of model expressed in the boundary representation (B-Rep) using the development tools of ObjectARX and MDT API offered by Autodesk Inc. The picking-up information makes it successful to implement the adaptive slicing method.(3)The direct slicing data are processed in order to accurately extract and reconstruct the data information of the 2D contours. Based on it, the radius compensation of laser beam spot, the filling contours and the optimization of the scanning paths are all implemented.(4)Based on the mechanism of SLS (Selected Laser Sintering), a matching rule between scanning velocity and laser power is established so as to realize the laser power matching in different scanning velocities.(5)Aiming at the SLS technology, the relationship between the rotation angle of mirror and X, Y coordinates of scanning point are derived theoretically, according to which the CLI file can be translated into PMAC instructors.(6)Considering the SLS technological characteristics and according to the PMAC instructor rules, the automatic conversion of the CLI file into the PMAC movement program is accomplished. In the meantime, a NC system scheme for rapid prototyping machine is designed for the SLS technology based on PMAC.(7)Based on the Windows operating system, all the functional modules above are developed and integrated with Visual C++ and ObjectARX in DMT 6.0 environment. This may be relatively good integration software for RP.The work of this thesis will be theoretically and practically beneficial to improving the part quality, boosting the forming efficiency and realizing the integration of CAD, CAPP and RP.