Layer-to-layer height control of Laser Metal Deposition processes

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.

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Variable Powder Flow Rate Control in Laser Metal Deposition Processes

ASME 2008 Dynamic Systems and Control Conference, Parts A and B ◽

10.1115/dscc2008-2112 ◽

2008 ◽

Author(s):

Lie Tang ◽

Jianzhong Ruan ◽

Robert G. Landers ◽

Frank Liou

Keyword(s):

Transport System ◽

Flow Rate ◽

Rate Control ◽

Metal Deposition ◽

Powder Flow ◽

Laser Metal Deposition ◽

Motion System ◽

Powder Flow Rate ◽

Deposition Processes ◽

Flow Rate Control

This paper proposes a novel method, called Variable Powder Flow Rate Control (VPFRC), for the regulation of powder flow rate in laser metal deposition processes. The idea of VPFRC is to adjust the powder flow rate to maintain a uniform powder deposition per unit length even when disturbances occur (e.g., the motion system accelerates and decelerates). Dynamic models of the powder delivery system motor and the powder transport system (i.e., five–meter pipe, powder dispenser, and cladding head) are constructed. A general tracking controller is then designed to track variable powder flow rate references. Since the powder flow rate at the nozzle exit cannot be directly measured, it is estimated using the powder transport system model. The input to this model is the DC motor rotation speed, which is estimated on–line using a Kalman filter. Experiments are conducted to examine the performance of the proposed control methodology. The experimental results demonstrate that the VPFRC method is successful in maintaining a uniform track morphology, even when the motion system accelerates and decelerates.

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Melt Pool Temperature Control for Laser Metal Deposition Processes—Part I: Online Temperature Control

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4000882 ◽

2010 ◽

Vol 132 (1) ◽

Cited By ~ 37

Author(s):

Lie Tang ◽

Robert G. Landers

Keyword(s):

Temperature Control ◽

Process Parameters ◽

Process Model ◽

Dynamic Balance ◽

Metal Deposition ◽

Time Varying ◽

Laser Metal Deposition ◽

Melt Pool ◽

Melt Pool Temperature ◽

Deposition Processes

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.

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Interplay between powder catchment efficiency and layer height in self-stabilized laser metal deposition

Optics and Lasers in Engineering ◽

10.1016/j.optlaseng.2021.106817 ◽

2022 ◽

Vol 149 ◽

pp. 106817

Author(s):

Simone Donadello ◽

Valentina Furlan ◽

Ali Gökhan Demir ◽

Barbara Previtali

Keyword(s):

Metal Deposition ◽

Laser Metal Deposition ◽

Layer Height

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

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4000883 ◽

2010 ◽

Vol 132 (1) ◽

Cited By ~ 15

Author(s):

Lie Tang ◽

Robert G. Landers

Keyword(s):

Temperature Control ◽

Heat Input ◽

Laser Power ◽

Process Model ◽

Metal Deposition ◽

Laser Metal Deposition ◽

Melt Pool ◽

Power Profile ◽

Melt Pool Temperature ◽

Deposition Processes

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.

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Melt pool temperature modeling and control for Laser Metal Deposition processes

2009 American Control Conference ◽

10.1109/acc.2009.5160415 ◽

2009 ◽

Author(s):

Lie Tang ◽

Robert G. Landers

Keyword(s):

Metal Deposition ◽

Laser Metal Deposition ◽

Modeling And Control ◽

Melt Pool ◽

Temperature Modeling ◽

Melt Pool Temperature ◽

Deposition Processes ◽

And Control

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Variable Powder Flow Rate Control in Laser Metal Deposition Processes

Journal of Manufacturing Science and Engineering ◽

10.1115/1.2953074 ◽

2008 ◽

Vol 130 (4) ◽

Cited By ~ 18

Author(s):

Lie Tang ◽

Jianzhong Ruan ◽

Robert G. Landers ◽

Frank Liou

Keyword(s):

Transport System ◽

Flow Rate ◽

Rate Control ◽

Metal Deposition ◽

Powder Flow ◽

Laser Metal Deposition ◽

Motion System ◽

Powder Flow Rate ◽

Deposition Processes ◽

Flow Rate Control

This paper proposes a novel method, called variable powder flow rate control (VPFRC), for the regulation of powder flow rate in laser metal deposition processes. The idea of VPFRC is to adjust the powder flow rate to maintain a uniform powder deposition per unit length even when disturbances occur (e.g., the motion system accelerates and decelerates). Dynamic models of the powder delivery system motor and the powder transport system (i.e., 5m pipe, powder dispenser, and cladding head) are constructed. A general tracking controller is then designed to track variable powder flow rate references. Since the powder flow rate at the nozzle exit cannot be directly measured, it is estimated using the powder transport system model. The input to this model is the dc motor rotation speed, which is estimated online using a Kalman filter. Experiments are conducted to examine the performance of the proposed control methodology. The experimental results demonstrate that the VPFRC method is successful in maintaining a uniform track morphology, even when the motion system accelerates and decelerates.

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