EBM variable direction forming dynamic slicing method cooperated with 840D numerical control system

Abstract

The invention discloses an EBM variable direction forming dynamic slicing method cooperated with an 840D numerical control system. The EBM variable direction forming dynamic slicing method comprises the steps of establishing a vertex array object VAO, adjusting a projection matrix to the slicing height during rendering of a three-dimensional model and outputting a two-dimensional section binary image through a reverse ray tracing algorithm; acquiring data of a contour line from the binary image through a two-dimensional contour extraction method, outputting coordinates of an end-to-end closedcontour, connecting all adjacent coordinates into straight lines and connecting all the straight lines end to end to form a closed curve; and dividing the contour data into a straight line part and acurve part with the starting point of the small straight lines with the included angle of 140 degrees as the segmentation point when the triangle tolerance is one, removing neighbor points, repeated points and internal points of the same straight lines, conducting segmentation fitting on a slicing data curve through a NURBS curve and then conducting dynamic slicing through the 840D numerical control system. Through the EBM variable direction forming dynamic slicing method, the computing time and conversion errors of STL files are reduced, and meanwhile, the phenomenon of over-accumulation of straight line inflection points is reduced.

Description

technical field [0001] The invention belongs to the technical field of rapid prototyping, and in particular relates to a dynamic slicing method for EBM direction-changing forming in cooperation with an 840D numerical control system. Background technique [0002] Electron beam additive manufacturing (EBM) is widely used in the rapid manufacture of precision blank parts in the aerospace field. [0003] (1) The traditional forming method is to slice the STL file according to the specified height before processing, and it is difficult to adjust the slice height according to the actual thickness. The main limiting factor is that the single-layer slicing time is too long, which is easy to damage the forming pace; [0004] (2) Direct slicing of STL files produces too many small straight lines, and the motor starts and stops frequently during the forming process, resulting in "jitter" of the electron gun. [0005] (3) When the curvature of the curve is large, the forming method of ...

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Problems solved by technology

[0003] (1) The traditional forming method is to slice the STL file according to the specified height before processing, and it is difficult to adjust the slice height according to the actual thickness. The main limiting factor is that the single-layer slicing time is too long, which is easy to damage the forming pace;

[0004] (2) Direct slicing of STL files produces too many small straight lines, and the motor starts and stops frequently during the forming process, resulting in "vibration" of the electron gun

[0005] (3) When the curvature of the curve is large, the forming method of micro-straight line approximation will produce metal over-accumulation at the inflection point, such as figure 2 shown, causing forming to fail to continue

[0006] (4) The traditional 3-axis machine tool cannot adjust the forming posture according to the curvature change of the model. For large-curvature transition parts or overhanging parts, additional support design needs to be added. However, the energy input in EBM forming is huge and the width of the single-pass molten pool is about 5mm. Resulting in support structures that cannot be easily removed and are therefore not suitable for adding supports;

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