Abstract: Aiming at the problem of the traditional additive manufacturing slicing algorithm easily leading to the distortion of the contour lines of the STL models of complex surface parts, a layered section contour generation algorithm for complex surface parts based on the NURBS curve is proposed. Aiming at the characteristics of large quantity of STL model data and slow layering speed, an intersection algorithm based on grouping and ranking is used to layer models, which could generate the point cloud data of the cross-sectional profile. The intersection points of the tangent plane and the STL triangle facet are used as the data points of the NURBS curve, and the weight of the data points is set. The weight factor of the NURBS curve is determined by the matrix form and the cut loss boundary conditions, and the control vertices of the NURBS curve is solved. The NURBS curve equation corresponding to the contour lines of each slicing layer are established in a matrix form, and the layer contours based on the NURBS curve are drawn. The layered section contour generation algorithm for complex surface parts based on NURBS curves is adopted to perform layering simulation and error analysis on the gas turbine medium-pressure cylinder moving blade and Ganesha model. Finally, a printing experiment of the gas turbine medium-pressure cylinder moving blade is performed. The test results show that profile deviation value of the blade printed by the algorithm of this study met the requirements and its accuracy is higher compared with the blade printed by traditional algorithm. It can be seen that layered section contour generation algorithm for complex surface parts based on the NURBS curve proposed here is feasible and accurate.

Key words: additive manufacturing, complex surface, grouping and ranking, non-uniform rational b-spline, slicing algorithm