Research Papers

Automatic Toolpath Generation for Heterogeneous Objects Manufactured by Directed Energy Deposition Additive Manufacturing Process

[+] Author and Article Information
Xinyi Xiao

Department of Industrial and
Manufacturing Engineering,
The Pennsylvania State University,
University Park, PA 16801
e-mail: xfx5020@psu.edu

Sanjay Joshi

Department of Industrial and
Manufacturing Engineering,
The Pennsylvania State University,
University Park, PA 16801
e-mail: sbj4@psu.edu

Manuscript received August 7, 2017; final manuscript received February 20, 2018; published online April 6, 2018. Assoc. Editor: Sam Anand.

J. Manuf. Sci. Eng 140(7), 071005 (Apr 06, 2018) (12 pages) Paper No: MANU-17-1503; doi: 10.1115/1.4039491 History: Received August 07, 2017; Revised February 20, 2018

A heterogeneous object (HO) refers to a solid component consisting of two or more material primitives distributed either continuously or discontinuously within the object. HOs are commonly divided into three categories. The first category has distinct material domains separating the different materials. The second, called functionally graded materials (FGMs), has continuous variation of material composition that produces gradient in material properties. The third category allows for any combinations of the first two categories within the same part. Modeling and manufacturing of HOs has recently generated more interest due to the advent of additive manufacturing (AM) technology that makes it possible to build such parts. Directed energy deposition (DED) processes have the potential for depositing multiple powdered materials in various compositions in the process of creating a single layer of material. To make this possible, tool paths that provide proper positioning of the deposition head and proper control over the material composition are required. This paper presents an approach for automatically generating the toolpath for any type of HO considering the material composition changes that are required on each layer. The toolpath generation takes into account the physical limitations of the machine associated with powder delivery and ability to continually grade the materials. Simulation results using the toolpath generation methodology are demonstrated by several example parts.

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Fig. 1

Direct energy deposition process scheme [1]

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Fig. 2

FGM representation varied in dimensional linear, nonlinear change in material distribution

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Fig. 3

Three categories of HO parts: (a) discrete multimaterial part, (b) linear FGM part, and (c) FGM part with partial heterogeneous material part

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Fig. 4

Slice representation of a hook with material changing in 2D plane

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Fig. 5

Toolpath in one slice: (a) linear, (b) zigzag, and (c) contour [14]

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Fig. 6

(a) Type I, scheme of laser deposition process [1] and (b) type II, scheme of LENS powder feeding process

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Fig. 7

Toolpath generation flowchart

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Fig. 8

(a) and (b): 2D radial material change from the center (3D model and one slice view) and (c) and (d): Materials distributed with distinct boundary (3D model and one slice view)

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Fig. 9

Examples of choosing different staring points on first slice

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Fig. 10

Algorithm of calculating next pixel laser traveling time and material switch time

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Fig. 11

Algorithm of choosing next optimal pixel position when the laser stops and the nozzle repositions itself without depositing materials

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Fig. 12

(a) FGM part with linear material gradient along with x-axis and (b) single slice view along with XY plane in Z height = 0.5 in

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Fig. 13

(a) Discrete multimaterial part with two materials in diffusion reaction pattern and (b) Single slice view along with XY plane in Z height = 0.1 in

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Fig. 14

(a) FGM part has two directions of material gradients with a homogenous material section and (b) single slice view along with XZ plane in Y-axis = 0.5 in

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Fig. 15

(a) FGM cylinder with material change radically and (b) single slice view along with XY plane in Z-axis = 0.2 in

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Fig. 16

Toolpath in XY slice for FGM part shown in Fig. 12

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Fig. 17

Toolpath in circle with rapid laser travel speed = 500 mm/s, switching material time = 11.2 s

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Fig. 18

Toolpath in circle with rapid laser travel speed = 100 mm/s, switching material time = 11.2 s

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Fig. 19

Toolpath in XY slice for HO part shown in Fig. 13

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Fig. 20

Toolpath shown in circle in Fig. 19

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Fig. 21

Toolpath in YZ slice for FGM part shown in Fig. 14

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Fig. 22

Toolpath shown in circle in Fig. 21 at laser scanning speed = 40 mm/s and fast traveling speed = 200 mm/s

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Fig. 23

Toolpath shown in circle in Fig. 21 at laser scanning speed = 60 mm/s and fast traveling speed = 150 mm/s

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Fig. 24

Toolpath in XY slice for FGM part shown in Fig. 15

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Fig. 25

Cylinder with two hollow cylinders slice view

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Fig. 26

Toolpath generation for the slice shown in Fig. 25



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