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Advanced Slicing Approaches

by Botao Zhang last modified 2016-08-29 14:43

  • Direct CAD slicing using Image Processing algorithm: IPSlicer
  • 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.

    Figure: Direct CAD slicing using Image Processing algorithm: IPSlicer

  • A K-D Tree Based Clustered Adaptive Layering Approach to Improve Part Accuracy by Varying Slice Thickness
  • A new approach of determining the variable slices using a 3D k-d tree method has been proposed in this research. The proposed approach is validated for three test parts and by comparing the volumetric, cylindricity, sphericity, and profile errors obtained from this approach with those obtained using a uniform slicing method.
    Since current AM machines are incapable of handling adaptive slicing approach directly, a “pseudo” grouped adaptive layering approach is also proposed here. This “clustered slicing” technique will enable the fabrication of a part in bands of varying slice thicknesses with each band having clusters of uniform slice thicknesses.

    Figure: K-D Tree based Adaptive Slicing and Slice Thickness based Clustering of Slices

  • Adaptive Slicing in Additive Manufacturing Process Using a Modified Boundary Octree Data Structure (MBODS)
  • This method, termed as modified boundary octree data structure (MBODS) algorithm, is used to convert the stereolithography (STL) file of an object to an octree data structure based on the part’s geometry, the machine parameters, and a user defined tolerance value.
    A subsequent algorithm computes the variable slice thicknesses using the MBODS representation of the part and virtually manufactures the part using these calculated slice thicknesses. Points sampled from the virtually manufactured part are inspected to evaluate the volumetric, profile, and cylindricity part errors

    Figure: Part Representation by MBODS

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