Study on Evolution Behavior of Geometrical Accuracy Based on Dynamic Characteristics of Molten Pool in Laser-based Direct Energy Deposition

Tang, Zijue; Liu, Weiwei; Yan, Zhaorui; Wang, Hao; Zhang, Hongchao

doi:10.3901/jme.2019.15.039

Cited by 14 publications

(4 citation statements)

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“…When using MP video diagnostics, there are a number of interfering factors, which include: Luminescent glow of oxides or slag on the MP surface, glow of plasma and metal vapors and reflection of laser radiation from the melt surface [22,28,29]. The use of selective optical filters makes it possible to exclude or reduce the influence of these factors.…”

Section: Methodsmentioning

confidence: 99%

Short Time Correlation Analysis of Melt Pool Behavior in Laser Metal Deposition Using Coaxial Optical Monitoring

Zavalov

Dubrov

2021

Sensors

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The development and improvement of monitoring and process control systems is one of the important ways of advancing laser metal deposition (LMD). The control of hydrodynamic, heat and mass transfer processes in LMD is extremely important, since these processes directly affect the crystallization of the melt and, accordingly, the microstructural properties and the overall quality of the synthesized part. In this article, the data of coaxial video monitoring of the LMD process were used to assess the features of melt dynamics. The obtained images were used to calculate the time dependences of the characteristics of the melt pool (MP) (temperature, width, length and area), which were further processed using the short-time correlation (STC) method. This approach made it possible to reveal local features of the joint behavior of the MP characteristics, and to analyze the nature of the melt dynamics. It was found that the behavior of the melt in the LMD is characterized by the presence of many time periods (patterns), during which it retains a certain ordered character. The features of behavior that are important from the point of view of process control systems design are noted. The approach used for the analysis of melt dynamics based on STC distributions of MP characteristics, as well as the method for determining the moments of pattern termination through the calculation of the correlation power, can be used in processing the results of online LMD diagnostics, as well as in process control systems.

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Section: Methodsmentioning

confidence: 99%

Short Time Correlation Analysis of Melt Pool Behavior in Laser Metal Deposition Using Coaxial Optical Monitoring

Zavalov

Dubrov

2021

Sensors

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“…Orthogonal experiments are used as the design tool to streamline experimental steps and improve data utilization. According to the previous research [20] , the process parameters are selected as shown in Tab 3. area, it is necessary to calibrate the shooting of the CMOS camera. Since the CMOS camera used in this paper is positioned perpendicular to the deposition substrate, the distortion caused by the camera angle is negligible.…”

Section: Controllability Analysismentioning

confidence: 99%

“…Considering the molten pool is approximately a semi-elliptical model [19] , at present, researches mainly focus on closed-loop control of molten pool width and height. However, molten pool area, as an instantaneous characteristic parameter that can comprehensively characterize the dynamic balance of melting, flow, and solidification of the molten pool [20] , has a coupling relationship between molten pool length, width, and height [21] . Relevant research is still lacking at present.…”

Section: Introductionmentioning

confidence: 99%

Real-time closed-loop control of molten pool transient area in direct laser deposition via PID algorithm with enhanced robustness

Liu,

Xia

et al. 2024

Int J Adv Manuf Technol

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In the direct laser deposition (DLD) process, it is common to employ constant processing parameters. The utilization of the constant parameters may lead to fluctuations in the dynamic evolution of the molten pool, primarily due to the intricate thermal effects involved, which will significantly impact the processing quality. To address this issue, this study proposed a closedloop control approach that effectively modifies processing parameters in real-time by targeting on the molten pool transient area. The most suitable processing parameter to control the molten pool area was found to be the laser power by a set of orthogonal experiments. Then the dynamic response relationship between laser power and the molten pool area was mathematically characterized by a third-order transfer function model to simplify the complex physical model of the DLD process. Subsequently, a PID controller with a filtering coefficient and anti-windup compensation was chosen compared with the other controller. In the validation experiments, it was observed that the closed-loop processing group demonstrated improved stability in maintaining the molten pool transient area, with a notable decrease of 33.7% in variability compared to the open-loop processing group. As a result, the deposited layer of the closed-loop processing group exhibited a much more satisfying surface quality and heat affect zone than the open-loop group. This study provides a fundamental basis for improving the consistency of the direct laser deposition processing quality through the implementation of real-time feedback control of molten pool physics.

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“…Following the previous work that studied the influence of different laser powers and scanning speeds on the state of a single-track melt pool [35], this paper divides the state of the melt pool into four categories: overheating (OH), intact (IT), irregularity (IR), and incomplete (IC).…”

Section: Data Collection and Pre-processingmentioning

confidence: 99%

In-suit monitoring melt pool states in direct energy deposition using ResNet

Liu¹,

Yuan²,

Peng³

et al. 2022

Meas. Sci. Technol.

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One critical challenge of directed energy deposition (DED) in additive manufacturing (AM) is the lack of comprehension of the relationship between the part parameters and the formation quality. Components fabricated by the inappropriate manufacturing parameters will be too unreliable to satisfy the strict requirements of industrial applications. To address these issues, the present study established an experiment with a coaxial high-speed CCD camera to monitor the 316L deposition process and developed a data-driven model with ResNet101 to identify different melt pool states. We adopted the t-distributed Stochastic Neighbor Embedding (t-SNE) clustering algorithm, accuracy rate, and normalized confusion matrix (NCM) to evaluate the performance of ResNet101. Furthermore, the visualization technique class activation mapping (CAM) was used to analyze the morphological characteristics of the melt pool formed under different experimental parameters, explained the classification behavior of the ResNet101 model. The result indicated that RseNet101 gains better feature extraction and higher capability to classify different melt pool states with an average accuracy of 99.07%, compared with other CNNs (LeNet, GoogLeNet, AlexNet, ResNet34, and ResNet50) model. This demonstrated the effectiveness of ResNet101 in monitoring the DED process and the potential to reduce fabrication costs in DED.

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Study on Evolution Behavior of Geometrical Accuracy Based on Dynamic Characteristics of Molten Pool in Laser-based Direct Energy Deposition

Cited by 14 publications

References 0 publications

Short Time Correlation Analysis of Melt Pool Behavior in Laser Metal Deposition Using Coaxial Optical Monitoring

Short Time Correlation Analysis of Melt Pool Behavior in Laser Metal Deposition Using Coaxial Optical Monitoring

Real-time closed-loop control of molten pool transient area in direct laser deposition via PID algorithm with enhanced robustness

In-suit monitoring melt pool states in direct energy deposition using ResNet

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