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Sam Anand - One of the best experts on this subject based on the ideXlab platform.

  • Additive Manufacturing Distortion Compensation Based on Scan Data of Built Geometry
    Journal of Manufacturing Science and Engineering-transactions of The Asme, 2020
    Co-Authors: Matthew Mcconaha, Sam Anand
    Abstract:

    Abstract Additive manufacturing (AM) processes such as direct metal laser sintering (DMLS) are highly attractive manufacturing processes due to the ability to create certain geometries which would be prohibitive or even impossible to manufacture by other means. However, with such high thermal gradients which are usually present in these processes, manufacturing distortions may result in the creation of unacceptable parts. This paper presents an approach to compensate input Stl Files based on registration of the point cloud from sacrificial part builds. A novel strain energy based non-rigid registration algorithm has been developed for robust registration of data points to the original computer-aided design (CAD) model. A neural network based approach is used to learn the deformation of the geometry based on the deviation of the scan geometry. This network is subsequently used to modify the Stl File to generate a new compensated Stl File. The compensated Stl File was validated by building parts and comparing the change in the part distortion.

  • Geometric Approaches to Input File Modification for Part Quality Improvement in Additive Manufacturing
    Journal of Manufacturing Processes, 2015
    Co-Authors: Sam Anand
    Abstract:

    Abstract Additive manufacturing (AM) machines use the Stereolithography (Stl) File as standard input File format to build parts. Stl model is a triangular faceted approximation of a CAD model, which represents a part with less accuracy than the CAD model. Commercial softwares have the ability to convert a CAD File into an Stl File based on a user defined threshold value to uniformly convert the entire part body into triangular facets. Increasing the geometric accuracy of Stl models is typically accomplished by decreasing the user defined threshold value, which results in an increase in Stl File size. In this research, a Surface-based Modification Algorithm (SMA) that adaptively and locally increases the facet density of an Stl model is presented. The Surface-based Modification Algorithm is an error minimization approach to modify the Stl facets locally based on chordal error, cusp height and cylindricity error for cylindrical features and is typically able to achieve a smaller File size compared to uniform export option. A novel bounding box based algorithm is developed to calculate cusp height error from the point cloud generated from the part by slicing the Stl facets or from the CAD surface. Final results show a distinct improvement in the part error of the Stl model using Surface-based Modification Algorithm (SMA) when compared to the original Stl File.

  • Increasing Part Accuracy in Additive Manufacturing Processes Using a k-d Tree Based Clustered Adaptive Layering
    Journal of Manufacturing Science and Engineering, 2014
    Co-Authors: Neeraj Panhalkar, Ratnadeep Paul, Sam Anand
    Abstract:

    Additive manufacturing (AM) is widely used in aerospace, automobile, and medical industries for building highly accurate parts using a layer by layer approach. The stereolithography (Stl) File is the standard File format used in AM machines and approximates the three-dimensional (3D) model of parts using planar triangles. However, as the Stl File is an approximation of the actual computer aided design (CAD) surface, the geometric errors in the final manufactured parts are pronounced, particularly in those parts with highly curved surfaces. If the part is built with the minimum uniform layer thickness allowed by the AM machine, the manufactured part will typically have the best quality, but this will also result in a considerable increase in build time. Therefore, as a compromise, the part can be built with variable layer thicknesses, i.e., using an adaptive layering technique, which will reduce the part build time while still reducing the part errors and satisfying the geometric tolerance callouts on the part. This paper describes a new approach of determining the variable slices using a 3D k-d tree method. The paper validates the proposed k-d tree based adaptive layering approach for three test parts and documents the results 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. The proposed k-d tree based adaptive slicing approach along with clustered slicing has been validated with simulations of the test parts of different shapes.

  • Error Minimization in Layered Manufacturing Parts by Stereolithography File Modification Using a Vertex Translation Algorithm
    Journal of Manufacturing Science and Engineering-transactions of The Asme, 2013
    Co-Authors: Gaurav Navangul, Ratnadeep Paul, Sam Anand
    Abstract:

    Layered manufacturing (LM) machines use stereolithography (Stl) Files to build parts by creating continuous slices on top of each other. An Stl File approximates the surface of a part with planar triangles. This results in geometric errors being introduced in the part surface during the conversion from the CAD model to the Stl File format, which in turn leads to errors in the LM manufactured part. CAD packages have built-in export options to reduce this CAD to Stl conversion error. However, this is applied to the entire part geometry which leads to an increase in the File size and preprocessing time in LM machines. This paper presents a new approach to locally reduce this CAD to Stl translation error. This approach, referred to as vertex translation algorithm (VTA), compares an Stl facet to its corresponding CAD surface, computes the chordal error at multiple points on the Stl surface, and translates the point with the maximum chordal error until it lies on the design surface. This translation results in the reduction of the chordal error locally without unnecessarily increasing the size of the Stl File. In addition, a facet isolation algorithm (FIA) has also been developed and presented in this paper. This isolation algorithm extracts the Stl facets corresponding to the surfaces and features of the part that have to be modified by the translation algorithm. The VTA is applied in conjunction with the FIA on a sample service part to reduce the form and proFile error of critical features of the part in order to satisfy the tolerance callouts on the part.

  • a vertex translation algorithm for adaptive modification of Stl File in layered manufacturing
    ASME 2011 International Manufacturing Science and Engineering Conference Volume 1, 2011
    Co-Authors: Gaurav Navangul, Ratnadeep Paul, Sam Anand
    Abstract:

    Rapid Prototyping (RP)/Layered Manufacturing (LM) machines typically use a Stereolithography (Stl) File as a basis to manufacture parts. However, the conversion of the part CAD File to Stl results in the distortion of the part geometry, particularly if the part consists of freeform curved surfaces. Existing algorithms and software tend to reduce this distortion globally, which increases the size and memory requirements of the Stl File. This paper presents a new approach for reducing the CAD to Stl translation error locally, using chordal error as the criteria. The algorithm presented here compares the Stl File to the design surface of the part, expressed as a NURBS surface, and computes the chordal error for multiple points on the Stl facets. The point within each Stl facet having the largest chordal error is modified to coincide with its corresponding point on the design surface. This replaces the original facet of the Stl File with three new facets with significantly lower chordal error than that of the original facet. This Vertex Translation Algorithm (VTA), reduces the chordal error in areas with high curvature and areas having tighter proFile tolerance specifications and provides the user the flexibility to selectively modify the Stl File according to the tolerance requirements. The algorithm has been validated with the help of a test case.Copyright © 2011 by ASME

Lanka Krishnanand - One of the best experts on this subject based on the ideXlab platform.

  • improve the accuracy surface smoothing and material adaption in Stl File for rp medical models
    Journal of Manufacturing Processes, 2016
    Co-Authors: A Manmadhachary, Ravi Y Kumar, Lanka Krishnanand
    Abstract:

    Abstract Manufacturing of accurate medical models from Digital Imaging and Communication in Medicine (DICOM) images is one of the useful techniques in case of complex medical surgeries. The DICOM images (voxels based data) were transformed into STereo Lithography (Stl) File (triangle based data) format. This is used for manufacturing of medical models with Rapid Prototyping (RP) technologies. However, there are always chances of having some defects like inaccuracy and rough surface finish of the RP model due to erroneous in Stl File. The proposed smoothing g algorithm is developed with combination of interpolation and mesh construction methods were used for producing an accurate and smoother Stl File. The proposed smoothening algorithm was implanted on dry mandible Stl File in the current study. The dry mandible Stl File is primarily split into slices of equal thickness along the Z -axis direction. Each slice contour data information was created as a Common Layer Interface (CLI) File. These contour data points are increased further improved contour accuracy by Fast Fourier Transform (FFT) method. As well as, these contour data points are used to generate a surface and Stl File simultaneously by the Delaunay triangulation method. By applying this novel combination method, the generated Stl File accuracy and smoothness were improved when compared to the initial Stl File. Furthermore, this algorithm is applicable for trimming and hole-filling operations in Stl Files by changing the triangulation angle.

Brent E Stucker - One of the best experts on this subject based on the ideXlab platform.

  • Software Issues for Additive Manufacturing
    Additive Manufacturing Technologies, 2015
    Co-Authors: Ian Gibson, David W Rosen, Brent E Stucker
    Abstract:

    This chapter deals with the software that is commonly used for additive manufacturing technology. In particular we will discuss the Stl File format that is commonly used by many of the machines to describe the model input data. These Files are manipulated in a number of machine-specific ways to create slice data and for support generation and the basic principles are covered here including some discussion on common errors and other software that can assist with Stl Files. Finally, we consider some of the limitations of the Stl format and how it may be replaced by something more suitable in the future like the newly developed Additive Manufacturing File format.

L I Aiping - One of the best experts on this subject based on the ideXlab platform.

A Manmadhachary - One of the best experts on this subject based on the ideXlab platform.

  • improve the accuracy surface smoothing and material adaption in Stl File for rp medical models
    Journal of Manufacturing Processes, 2016
    Co-Authors: A Manmadhachary, Ravi Y Kumar, Lanka Krishnanand
    Abstract:

    Abstract Manufacturing of accurate medical models from Digital Imaging and Communication in Medicine (DICOM) images is one of the useful techniques in case of complex medical surgeries. The DICOM images (voxels based data) were transformed into STereo Lithography (Stl) File (triangle based data) format. This is used for manufacturing of medical models with Rapid Prototyping (RP) technologies. However, there are always chances of having some defects like inaccuracy and rough surface finish of the RP model due to erroneous in Stl File. The proposed smoothing g algorithm is developed with combination of interpolation and mesh construction methods were used for producing an accurate and smoother Stl File. The proposed smoothening algorithm was implanted on dry mandible Stl File in the current study. The dry mandible Stl File is primarily split into slices of equal thickness along the Z -axis direction. Each slice contour data information was created as a Common Layer Interface (CLI) File. These contour data points are increased further improved contour accuracy by Fast Fourier Transform (FFT) method. As well as, these contour data points are used to generate a surface and Stl File simultaneously by the Delaunay triangulation method. By applying this novel combination method, the generated Stl File accuracy and smoothness were improved when compared to the initial Stl File. Furthermore, this algorithm is applicable for trimming and hole-filling operations in Stl Files by changing the triangulation angle.