Research On Some Key Problems Of Software And Technology For Rapid Prototyping

Through over ten years'development, great progress has been made at Rapid Prototyping (RP) technology in China. However, there is still a large gap between the domestic and the international leading companies in some technologies. Some key subjects on the RP software and technique are investigated in this dissertation, which include Boolean operations on STL models, optimization of intersection test, automatic control of temperature for SLS system, mathematics modeling and numerical Calculation of Radiation Heating. The theories and achievements contribute to the development of the RP software and equipment of Huazhong University of Science and Technology, and provide a versatile software tool for the domestic promotion of Rapid Prototyping.The realization of Boolean operation on STL models is a bottleneck of developing the excellent RP data processing software. An algorithm is proposed to realize the Boolean operation of two STL models based on loop detection. The intersected triangle pairs and intersected segments are calculated by the intersection test. Detecting the loops for determination of the valid intersection lines improves the efficiency and the reliability of the process greatly. The intersected triangles and surfaces are divided into several surface patches along the intersection loops. The inclusion prediction between a surface patch and a STL solid is taken by testing a candidate point whether inside or outside the solid region of a slice at corresponding height. Boolean operation can offer a versatile tool for editing or modifying the STL model in three dimensions to solve the involved problems for the data processing of the RP application.In the process of Boolean operation of two solids, a direct computation of intersections between two surfaces by considering all the triangles on one surface against all the triangles on the other one is an inefficient algorithm. The spatial decomposition and hierarchical bounding volume trees technique are proposed to optimize the intersection test. The detail steps of the optimization algorithms are presented, which take respectively the space decomposition with cells of equal size and the AABB bounding volume trees. The two kinds of optimization ways are to find the potential intersected region or intersected triangle pairs by rejecting quickly the triangles that do not possibly have any intersection, which can reduce drastically the number of triangle pairs that have to be computed the intersection, and improve the efficiency of the performance.It is an important developing direction to produce the functional parts by sintering the polyamide composites, which has a broad application prospect. But the evenness of the temperature field cannot meet the need of temperature conditions of sintering the polyamide materials, which hinders the experimental research and the popularization of its application in China. The mathematic model is build for the tubular radiation heater of the HRPS series SLS systems, by which some diagrams are achieved through computing the distribution, evenness degree and maximum deviation of the temperature field at different mounting height of the heater. Some measures are put forward to improve the uniformity of the preheating temperature field according to the regularity summarized from the results of the numerical calculation. The analyzing method can be well used for reference to develop advanced heater with homogeneous energy distribution.It is a crucial problem to inhibit the curling of the parts, which is a ubiquitous destructive phenomenon in the process of Selective Laser Sintering the polymer materials. The conventional way in which the preheating temperature is adjusted manually, increases greatly the intensity of the labor, and affects the intelligence and automation level of the SLS system badly. According to the developing regularity of the curling, the layers are classified as general layers and key layers based on the different temperature requests. The means of combining of hardware and software is adopted to realize the functions of predicting the key layers, measuring of the temperature automatically, adjusting the speed of the heating-up or cooling and so on. Thereby the preheating temperature can be adjusted automatically according to different attribute of each layer, and the real automation of the SLS processing is implemented.