Abstract
Aiming at the problems of over stacking, warping deformation and rapid adjustment of layer thickness in electron beam additive manufacturing, the 3D printing slicing algorithm and partition scanning strategy for numerical control systems are studied. The GPU (graphics processing unit) is used to slice the 3D model, and the STL (stereolithography) file is calculated in parallel according to the normal vector and the vertex coordinates. The voxel information of the specified layer is dynamically obtained by adjusting the projection matrix to the slice height. The MS (marching squares) algorithm is used to extract the coordinate sequence of the binary image, and the ordered contour coordinates are output. In order to avoid shaking of the electron gun when the numerical control system is forming the microsegment straight line, and reduce metal overcrowding in the continuous curve C0, the NURBS (non-uniform rational b-splines) basis function is used to perform curve interpolation on the contour data. Aiming at the deformation problem of large block components in the forming process, a hexagonal partition and parallel line variable angle scanning technology is adopted, and an effective temperature and deformation control strategy is formed according to the European-distance planning scan order of each partition. The results show that the NURBS segmentation fits closer to the original polysurface cut line, and the error is reduced by 34.2% compared with the STL file slice data. As the number of triangular patches increases, the algorithm exhibits higher efficiency, STL files with 1,483,132 facets can be cut into 4488 layers in 89 s. The slicing algorithm involved in this research can be used as a general data processing algorithm for additive manufacturing technology to reduce the waiting time of the contour extraction process. Combined with the partition strategy, it can provide new ideas for the dynamic adjustment of layer thickness and deformation control in the forming process of large parts.
Highlights
The electron beam additive manufacturing process is similar to the arc welding nology, but its energy input is higher, and the rapid cooling and heating process where p1 0, p2 0, p3 0 is the projection of the three vertices of the triangular facet on the forming process more
The results show that when the triangle tolerance is one, large parts, NURBS basis functions are used to fit the contour data to ens the segmental fitting of the slice data through the spline basis function can reduce the constant forming line speed
The results show that when the triangle tolerance is on conversion error of the STL file by 34.2%, and at the same time reduce the over-stacking segmental fitting of the slice data through basis function reduce the co phenomenon of the inflection point of the straightthe line.spline
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In order to improve the efficiency of data processing and molding accuracy, a large number of research studies on Slicing Algorithm and scanning strategy have emerged. During the execution of the algorithm, it is necessary to classify the triangular patches or even establish the topological relationship between the patches, which causes a lot of wasted time For this reason, this article proposes a direct slicing technology of a 3D model based on GPU computing, which performs parallel coloring according to the normal vector and vertex coordinates of the triangular facets in the STL data, and changes the slice position by adjusting the projection matrix to the slice height. Due to the large size of the formed part, the traditional STL slicing algorithm needs a long data processing time in the preprocessing stage, which makes it difficult to meet the deformation control requirements of real-time data adjustment. (1) The reverse ray tracing algorithm is used to slice the 3D model in parallel, and the slice position or slice direction is adjusted in real time according to the height feedback information in the forming process. (2) According to the area of the forming layer and the thickness of the part, the number of zones and the scanning sequence of the zones are planned to make the temperature field distribution relatively uniform. (3) The NURBS basis function is used to fit the slice data, combined with the high-order curve processing commands of the CNC system, to reduce the amount of G code transmission while keeping the linear velocity constant
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