Image Processing Assisted Tools for Pre- and Post-Processing Operations in Additive Manufacturing

摘要

Additive Manufacturing (AM) or 3D printing (3DP) process is a layer by layer manufacturing approach for manufacturing parts with complex geometries. The STL (Stereolithography) file format is the defacto industry standard for manufacturing parts by AM/3DP. The STL file is a triangular mesh representation of CAD geometry in non-uniform rational B-spline (NURBS) surface format and thus is an approximation of actual part geometry. During the conversion of a complex CAD geometry to an STL file, geometric errors are introduced in the model. These drawbacks associated with the STL file may translate into a faulty or inaccurate final manufactured part. This paper presents a novel Image Processing (IP) based Direct CAD Slicer, IPSlicer, which can be used to manufacture components directly from CAD geometry (without converting to STL file). Using sectional image snapshots of a part, captured normal to the build direction and sectional 2D bounding box data, contour points for each section are identified by performing boundary tracing operation followed by application of Contour Mapping Algorithm (CMA). The method slices the actual NURBS geometry and thus parts manufactured by this method have reduced GD&T errors such as flatness, cylindricity, and profile error. In addition, a support removability analysis tool is developed by performing color-based segmentation on sectional image snapshots in conjunction with a pixel traversal approach. Using the segmented images and sectional bounding box, a sintering area and time calculation tool for each layer is also developed. The effectiveness of IPSlicer is verified by virtually manufacturing test components and calculating GD&T errors by the application of computational metrology algorithms on virtually manufactured data. The support removability analysis tool as well as sintering time and area calculator are validated using several test parts.