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Research Papers

Adaptive Slicing in Additive Manufacturing Process Using a Modified Boundary Octree Data Structure

[+] Author and Article Information
Nandkumar Siraskar

Center for Global Design and Manufacturing,
Department of Mechanical and
Materials Engineering,
University of Cincinnati,
Cincinnati, OH 45221
e-mail: siraskarns@gmail.com

Ratnadeep Paul

Center for Global Design and Manufacturing,
Department of Mechanical and
Materials Engineering,
University of Cincinnati,
Cincinnati, OH 45221
e-mail: paulrp@ucmail.uc.edu

Sam Anand

Center for Global Design and Manufacturing,
Department of Mechanical and
Materials Engineering,
University of Cincinnati,
Cincinnati, OH 45221
e-mail: sam.anand@uc.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received August 10, 2013; final manuscript received September 10, 2014; published online November 26, 2014. Assoc. Editor: Jack Zhou.

J. Manuf. Sci. Eng 137(1), 011007 (Feb 01, 2015) (11 pages) Paper No: MANU-13-1306; doi: 10.1115/1.4028579 History: Received August 10, 2013; Revised September 10, 2014; Online November 26, 2014

In additive manufacturing (AM) processes, the layer-by-layer fabrication leads to a staircase error resulting in dimensional inaccuracies in the part surface. Using thinner slices reduces the staircase error and improves part accuracy but also increases the number of layers and the build time for manufacturing the part. Another approach called adaptive slicing uses slices of varying thicknesses based on the part geometry to build the part. A new algorithm to compute adaptive slice thicknesses using octree data structure is presented in this study. 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. The MBODS based slicing algorithm is validated by comparing it with the uniform slicing approach using various slice thicknesses for different parts. The developed MBODS algorithm is observed to be more effective in improving the part quality while using lesser number of slices.

Copyright © 2015 by ASME
Topics: Algorithms , Errors , Octrees
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References

Figures

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Fig. 1

(a) Example 3D object, (b) octree decomposition, and (c) tree representation

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Fig. 2

(a) Part model, (b) quadtree representation, and (c) extended quadtree representation

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Fig. 3

Cube edge and triangle facet intersection

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Fig. 4

Cube face and triangle edge intersection

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Fig. 5

Cube with intersecting triangles parallel or perpendicular to the cube faces

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Fig. 6

Rays casted in a gray cube

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Fig. 7

Test to determine if point is (a) inside the part volume or (b) outside the part volume

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Fig. 8

Determination of point with no intersections

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Fig. 9

Segments for rays originating from points lying (a) outside the part and (b) inside the part

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Fig. 10

Slice thickness calculations

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Fig. 11

Division of a cube octant into multiple regions

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Fig. 12

Redivision of octant and calculation of residual slice thickness

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Fig. 13

Cube overlapping with already fixed slice thicknesses

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Fig. 14

(a) CAD model, (b) STL file, and (c) MBODS representation for test part 1

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Fig. 15

(a) CAD model, (b) STL file, and (c) MBODS representation for test part 2

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Fig. 16

(a) Test part 3, (b) MBODS representation, and (c) sampled points on virtually manufactured surface

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Fig. 17

(a) Surface under consideration in test part 1 and (b) points sampled from virtually manufactured surface

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Fig. 18

(a) STL format of cylinder with 45 deg the Z-axis and (b) Points dataset for cylindricity evaluation

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