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Research Papers

Melt Pool Temperature Control for Laser Metal Deposition Processes—Part II: Layer-to-Layer Temperature Control

[+] 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 132(1), 011011 (Jan 21, 2010) (9 pages) doi:10.1115/1.4000883 History: Received August 07, 2009; Revised December 17, 2009; Published January 21, 2010; Online January 21, 2010

Heat input regulation is crucial for deposition quality in laser metal deposition (LMD) processes. To control the heat input, melt pool temperature is regulated using temperature controllers. Part I of this paper showed that, although online melt pool temperature control performs well in terms of tracking the temperature reference, it cannot guarantee consistent track morphology. Therefore, a new methodology, known as layer-to-layer temperature control, is proposed in this paper. The idea of layer-to-layer temperature control is to adjust the laser power profile between layers. The part height profile is measured between layers, and the temperature is measured online. The data are then utilized to identify the parameters of a LMD process model using particle swarm optimization. The laser power profile is then computed using iterative learning control, based on the estimated process model and the reference melt pool temperature of the next layer. The deposition results show that the layer-to-layer temperature controller is capable of not only tracking the reference temperature, but also producing a consistent track morphology.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Layer-to-layer temperature controller structure

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Figure 2

Measured track height profiles for estimation performance experiment

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Figure 3

Measured temperature profiles for estimation performance experiment

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Figure 4

Experimental and simulation results comparison for estimation performance experiment (Layers 1 and 2)

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Figure 5

Laser power profile generation using ILC

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Figure 6

Layer eight temperature profile for experiment using q=736.4 W

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Figure 7

Layer eight temperature and power profiles using layer-to-layer temperature control; T—measured melt pool temperature; Tr—reference temperature; Ts—simulated temperature based on the computed laser power profile

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Figure 8

Layer eight temperature profile for experiment using q=736.4 W correlated with the track side view

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Figure 9

Frequency content of temperature measurement of layer eight in experiment using q=736.4 W

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Figure 10

Tracks deposited for experiment using layer-to-layer temperature control (top) and q=736.4 W (bottom)

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Figure 11

Height profiles for experiment using q=736.4 W

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Figure 12

Height profiles for experiment using layer-to-layer temperature control.

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Figure 13

Track morphology for experiment using q=736.4 W with three slice planes located at 8 mm, 29 mm, and 43 mm; –: first slice plane; – o: second slice plane; ◻: third slice plane

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Figure 14

Track morphology for experiment using layer-to-layer temperature control with three slice planes located at 8 mm, 29 mm, and 43 mm; –: first slice plane; – o: second slice plane; ◻: third slice plane

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Figure 15

Width cross sections in the vertical direction using three slices; constant laser power (left) and layer-to-layer temperature control (right); *: first slice plane; o: second slice plane; ◇: third slice plane.

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Figure 16

Width cross sections at the middle length of the track: track deposited using q=736.4 W (left) and track deposited using layer-to-layer temperature control (right)

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Figure 17

Deposition direction and sample position of the experiments with Tr=2140 K.

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Figure 18

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

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Figure 19

Transverse-section microstructure at the middle part of the sample deposited using q=736.4 W(400×)

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