Research Papers

Design of a New Parametric Path Plan for Additive Manufacturing of Hollow Porous Structures With Functionally Graded Materials

[+] Author and Article Information
Ibrahim T. Ozbolat

Mechanical and Industrial Engineering,
The University of Iowa,
2130 Seamans Center,
Iowa City, IA 52242
The Center for Computer-Aided Design,
The University of Iowa,
216 Engineering Research Facility,
Iowa City, IA 52242

A. K. M. B. Khoda

Industrial and Manufacturing
Engineering Department,
North Dakota State University,
202F CIE Building,
Fargo, ND 58102

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF COMPUTING AND INFORMATION SCIENCE IN ENGINEERING. Manuscript received August 1, 2013; final manuscript received August 17, 2014; published online September 10, 2014. Assoc. Editor: Charlie C.L. Wang.

J. Comput. Inf. Sci. Eng 14(4), 041005 (Sep 10, 2014) (13 pages) Paper No: JCISE-13-1144; doi: 10.1115/1.4028418 History: Received August 01, 2013; Revised August 17, 2014

In this paper, a novel path planning approach is proposed to generate porous structures with internal features. The interconnected and continuous deposition path is designed to control the internal material composition in a functionally graded manner. The proposed layer-based algorithmic solutions generate a bilayer pattern of zigzag and spiral toolpath consecutively to construct heterogeneous three-dimensional (3D) objects. The proposed strategy relies on constructing Voronoi diagrams for all bounding curves in each layer to decompose the geometric domain and discretizing the associated Voronoi regions with ruling lines between the boundaries of the associated Voronoi regions. To avoid interference among ruling lines, reorientation and relaxation techniques are introduced to establish matching for continuous zigzag path planning. In addition, arc fitting is used to reduce over-deposition, allowing nonstop deposition at sharp turns. Layer-by-layer deposition progresses through consecutive layers of a ruling-line-based zigzag pattern followed by a spiral path deposition. A biarc fitting technique is employed through isovalues of ruling lines to generate G1 continuity along the spiral deposition path plan. Functionally graded material properties are then mapped based on a parametric distance-based weighting technique. The proposed approach enables elimination or minimization of over-deposition of materials, nonuniformity on printed strands and discontinuities on the toolpath, which are shortcomings of traditional zigzag-based toolpath plan in additive manufacturing (AM). In addition, it provides a practical path for printing functionally graded materials.

Copyright © 2014 by ASME
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Fig. 1

Shortcomings of traditional toolpath planning in Cartesian coordinates such as jumps and independency of material blending direction from the deposition direction in Cartesian coordinates

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Fig. 2

(a) Voronoi diagram generation. (b) Voronoi cell contour for corresponding internal feature. (c) Voronoi cell contour for the external feature.

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Fig. 3

Curve matching and ruling line generation between the features and the Voronoi cells

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Fig. 4

Matching between property changing lines based on an objective function

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Fig. 5

Matching of property changing lines between Voronoi cells

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Fig. 6

Relaxation of property changing lines to alleviate over-deposition

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Fig. 7

(a) Arc fitting for smooth and uniform deposition and (b) arc fitted PCLs for smooth deposition

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Fig. 8

Simulation of toolpath plan in Rhinoceros 4.0 for the deposition along PCLs

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Fig. 9

Feasible PCLs for spiral path planning resulting in generation of knot points and piecewise spiral curve

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Fig. 10

Biarc fitting: (a) C-shape biarc, (b) S-shape biarc, and (c) determining number of points with error control

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Fig. 15

A porous structure: (a) a continuous toolpath with two-hollowing features, (b) the structure is designed in 3D; a complex-shaped structure: (c) a continuous toolpath with four internal hollowing features, (d) the structure is designed in 3D; another complex-shaped structure: (e) a continuous toolpath with a concave hollowing feature, and (f) the structure is designed in 3D.

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Fig. 14

A CAD model of an anonymous human heart is (a) sliced, and the new methodology is applied to generate continuous toolpath for a section enclosing right and left ventricle (b) based on the material requirements as functions of parametric distances from features. Toolpaths with (c) a double layer and (d) multiple layers are developed for demonstration purposes.

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Fig. 13

(a) Medical imaging is used to generate (b) a 3D CAD model of an aorta, which (c) is then sliced into layers for (d) and (e) toolpath generation in two consecutive steps based on material requirements defined by a function. (f) A 32-layer scaffold is also developed for demonstration purposes.

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Fig. 12

Femur bone CAD model is generated: (a) using medical imaging and then (b) sliced into layers. (c) The proposed methodology is applied based on material needs (d) to generate continuous toolpath for femoral artery section of the femur. (e) Uniform porosity, where the porous space is controlled by controlling the distance between zigzag and spiral curves by applying the algorithms developed in our earlier work [10].

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Fig. 11

Mapping of the material domain to the geometric domain by function g to obtain material composition




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