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Research Papers

Melt Pool Temperature Control for Laser Metal Deposition Processes—Part I: Online 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), 011010 (Jan 21, 2010) (9 pages) doi:10.1115/1.4000882 History: Received August 07, 2009; Revised December 17, 2009; Published January 21, 2010; Online January 21, 2010

Melt pool temperature is of great importance to deposition quality in laser metal deposition processes. To control the melt pool temperature, an empirical process model describing the relationship between the temperature and process parameters (i.e., laser power, powder flow rate, and traverse speed) is established and verified experimentally. A general tracking controller using the internal model principle is then designed. To examine the controller performance, three sets of experiments tracking both constant and time-varying temperature references are conducted. The results show the melt pool temperature controller performs well in tracking both constant and time-varying temperature references even when process parameters vary significantly. However a multilayer deposition experiment illustrates that maintaining a constant melt pool temperature does not necessarily lead to uniform track morphology, which is an important criteria for deposition quality. The reason is believed to be that different melt pool morphologies may have the same temperature depending on the dynamic balance of heat input and heat loss.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Laser metal deposition process system setup

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Figure 2

Measured and simulated temperatures and laser power profile for validation experiment with m=4 g/min and v=1.7 mm/s

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Figure 3

Melt pool temperature closed-loop control system block diagram

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Figure 4

Plots of filtered and measured temperature signals using Kalman filter (λ=0, Rγ=2500 K2, and Qw=25 K2) with m=4 g/min and v=1.7 mm/s

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Figure 5

Open-loop temperature response for Tr(t)=2100 K with q=537.6 W, m=6 g/min, and v=2.54 mm/s

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Figure 6

Closed-loop temperature response for Tr(t)=2100 K with m=6 g/min and v=2.54 mm/s

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Figure 7

Open-loop temperature response for Tr(t)=2100+50 sin(t) K with m=6 g/min and v=2.54 mm/s

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Figure 8

Closed-loop temperature response for Tr(t)=2100+50 sin(t) K with m=6 g/min and v=2.54 mm/s

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Figure 9

Time-varying traverse speed profile of a circular motion under command traverse speed of 2.54 mm/s (R=25.4 mm)

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Figure 10

Closed-loop temperature response for Tr(t)=2000 K for circular part with m=6 g/min and time-varying traverse speed given in Fig. 9

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Figure 11

Schematic of temperature sensor blockage when temperature sensor and deposition direction are parallel

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Figure 12

Closed-loop temperature response for Tr(t)=2000+100 sin(t) K for circular part with m=6 g/min and time-varying traverse speed shown in Fig. 9.

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Figure 13

Time-varying powder flow rate profile Pr(t)=6+2 sin(t) g/min

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Figure 14

Closed-loop temperature response for Tr(t)=2000 K with powder flow rate given in Fig. 1 and traverse speed profile in Fig. 9

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Figure 15

Closed-loop temperature response for Tr(t)=2000+100 sin(t) K with powder flow rate given in Fig. 1 and traverse speed profile given in Fig. 9

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Figure 16

Height profiles of five-layer deposition using online temperature control with m=6 g/min, v=2.54 mm/s, and Tr=2000 K

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Figure 17

Five-layer track deposited using online temperature control with m=6 g/min, v=2.54 mm/s, and Tr=2000 K

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Figure 18

Layer 1 temperature tracking results in multilayer deposition using online temperature control with m=6 g/min, v=2.54 mm/s, and Tr=2000 K

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Figure 19

Layer 5 temperature tracking results in multilayer deposition using online temperature control with m=6 g/min, v=2.54 mm/s, and Tr=2000 K

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Figure 20

Layer 5 temperature tracking results and track height profile of multilayer deposition experiment with m=6 g/min, v=2.54 mm/s, and Tr=2000 K

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Figure 21

Multilayer single track deposition using online temperature control with m=4 g/min, v=3.4 mm/s, and Tr=2275 K

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Figure 22

Layer 4 temperature tracking results using online temperature control with m=4 g/min, v=3.4 mm/s, and Tr=2275 K

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