Irregular Surface Fitting And Rapid Development Base On Phase Mearsurement

The 3D modeling, machining and rapid developing of irregular and complex surface have always been difficult for products design and manufacture, and it has become research emphasis recently. Combining reverse engineering and positive processing technology is a good way to solve these problems. It fundamentally changes the traditional mode for product development and manufacturing. It solves the difficulty in modeling and manufacturing for some complex products. It shortens the time to develop and machine new products. Thus point clouds acquisition and pre-processing, NURBS surface reconstruction and quality analysis, surface optimization algorithm and rapid developing of the products are studied in the paper.Firstly, acquisition and pre-processing technology for 3D point clouds data are studied. Some theories based on phase measurement, such as fringe projection, phase modulation, phase demodulation and phase unwrapping are analyzed.3D scanner calibration, object positioning and the acquisition process of point cloud data are implemented in the paper. Then the point clouds data is pre-processed. The data is compacted applying the maximum allowable deviation method with the precision of 40%. The important details of the morphology are effectively retained. In addition, noises elimination, data smoothing and segmentation of the point clouds are conducted.Secondly, NURBS surface fitting theory is studied, and the whole surface fitting and splicing are achieved. The maximum error of point clouds-surface is 0.270mm, which meets the requirement of high precision fitting. The least-square surface optimization algorithm based on orthogonal function is proposed according to the comparison results among several surface fitting methods. With the proposed algorithm, satisfactory fitting result can be achieved only by 36 control points of 4x4 orders, and the average error of reconstruction is only 0.0461mm. Therefore, the superiority of proposed method can be verified through the comprehensive comparison with the least-square method in such aspects as surface reconstruction precision and surface smoothness. The influence of surface order and the number of control points on reconstruction precision are studied through experiments. Moreover, the surface fitting method that reasonably selects the surface order according to the number of control points is proposed.Finally,3D punch and die for surface are designed, and NC machining is simulated. Through the post processing for source files of cutting track, the NC programs of fz37 CNC machines with CNC840D control system are generated. Therefore, secondary development for irregular surface components is achieved.