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Research Papers

Layer-to-Layer Height Control for Laser Metal Deposition Process

[+] Author and Article Information
Lie Tang

Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, MO 65401-0050ltx8d@mst.edu

Robert G. Landers

Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, MO 65401-0050landersr@mst.edu

J. Manuf. Sci. Eng 133(2), 021009 (Mar 15, 2011) (9 pages) doi:10.1115/1.4003691 History: Received December 17, 2009; Revised February 05, 2011; Published March 15, 2011; Online March 15, 2011

A laser metal deposition height control methodology is presented in this paper. The height controller utilizes a particle swarm optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. Using the estimated model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using iterative learning control (ILC). The model parameter estimation performance using PSO is evaluated using a four-layer single track deposition, and the powder flow rate reference generation performance using ILC is tested using simulation. The results show that PSO and ILC perform well in estimating model parameters and generating powder flow rate references, respectively. The proposed height control methodology is then tested experimentally for tracking a constant height reference with constant traverse speed and constant laser power. The experimental results indicate that the controller performs well in tracking constant height references in comparison with the widely used fixed process parameter strategy. The application of layer-to-layer height control produces more consistent layer height increment and a more precise track height, which saves machining time and increases powder efficiency.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 4

Experimental and simulation results for estimation performance test experiment (layers 1 and 2)

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Figure 5

Reference powder flow rate profile generation methodology

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Figure 6

Measured speed profile from execution of a clockwise circle (r=25.4 mm and v=4.23 mm/s) on CNC machine

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Figure 7

Layer height simulation result and corresponding powder flow rate profile generated by ILC for circular deposition (r=25.4 mm and v=4.23 mm/s)

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Figure 8

Height profiles for experiment using layer-to-layer height control (Hrt=5 mm)

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Figure 9

Height profiles for experiment using m=3.73 g/min(Hrt=5 mm)

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Figure 10

Track photos: using layer-to-layer height control (top) and using constant powder flow rate (bottom)

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Figure 11

Track morphology for track built using layer-to-layer height control with three slice planes located at 8 mm, 24 mm, and 40 mm, - ∗ is the first slice plane, -○ is the second slice plane, and -◇ is the third slice plane

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Figure 12

Track morphology for track built using m=3.73 g/min with three slice planes located at 8 mm, 24 mm, and 40 mm, - ∗ is the first slice plane, -○ is the second slice plane, and -◇ is the third slice plane

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Figure 13

Width cross sections comparison using three slices, from left: slice 1, slice 2, and slice3, ∗ is the layer-to-layer height control and ○ is the constant powder flow rate

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Figure 14

Width cross sections in the vertical and horizontal directions using three slices: layer-to-layer height control (left) and constant powder flow rate (right), ∗ is the first slice plane, ○ is the second slice plane, and ◇ is the third slice plane

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Figure 15

Transverse-section microstructure at middle part of the sample fabricated using layer-to-layer height control (400×)

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Figure 16

Transverse-section microstructure at middle part of the sample fabricated using constant powder flow rate (400×)

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Figure 17

Estimated temperature and height for layer 4 of experiment using layer-to-layer height control

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Figure 18

Layer 4 height and powder flow rate profiles using layer-to-layer height control: H is the measured layer height, Hr is the reference height, and Hs is the simulated height profile based on predicted powder flow rate profile

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Figure 1

Laser metal deposition process system

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Figure 2

Laser metal deposition height controller structure

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Figure 3

(a) Measured track height profiles for estimation performance test experiment and (b) measured temperature profiles for estimation performance test experiment

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