On-line melt pool temperature control in L-PBF additive manufacturing

2021 ◽  
Author(s):  
Hossein Rezaeifar ◽  
M. A. Elbestawi
Keyword(s):  
Additive Manufacturing ◽  
Temperature Control ◽  
Melt Pool ◽  
On Line ◽  
Melt Pool Temperature

Defect detection in additive manufacturing via a toolpath overlaid melt-pool-temperature tomography

2020 ◽  
Vol 32 (2) ◽  
pp. 022055
Author(s):  
R. Bernhard ◽  
P. Neef ◽  
H. Wiche ◽  
C. Hoff ◽  
J. Hermsdorf ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Defect Detection ◽  
Melt Pool ◽  
Melt Pool Temperature

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

2010 ◽  
Vol 132 (1) ◽  
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.

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

2010 ◽  
Vol 132 (1) ◽  
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.

In-situ monitoring of optical emission spectra for microscopic pores in metal additive manufacturing Submitted for Publication

2021 ◽  
pp. 1-21
Author(s):  
Wenbo Sun ◽  
Zhenhao Zhang ◽  
Wenjing Ren ◽  
Jyoti Mazumder ◽  
Jionghua (Judy) Jin
Keyword(s):  
Additive Manufacturing ◽  
Emission Spectra ◽  
Optical Emission ◽  
In Situ Monitoring ◽  
Melt Pool ◽  
Multiple Processes ◽  
Melt Pool Temperature ◽  
Optical Emission Spectra

Abstract Quality assurance techniques are increasingly demanded in additive manufacturing. Going beyond most of the existing research that focuses on the melt pool temperature monitoring, we develop a new method that monitors the in-situ optical emission spectra signals. Optical emission spectra signals have been showing a potential capability of detecting microscopic pores. The concept is to extract features from the optical emission spectra via deep auto-encoders, and then cluster the features into two quality groups to consider both unlabelled and labelled samples in a semi-supervised manner. The method is integrated with multitask learning to make it adaptable for the samples collected from multiple processes. Both a simulation example and a case study are performed to demonstrate the effectiveness of the proposed method.

scholarly journals Additive Manufacturing of Bulk Nanocrystalline FeNdB Based Permanent Magnets

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 538
Author(s):  
Dagmar Goll ◽  
Felix Trauter ◽  
Timo Bernthaler ◽  
Jochen Schanz ◽  
Harald Riegel ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Melt Spinning ◽  
Permanent Magnets ◽  
Maximum Energy ◽  
Laser Melting ◽  
Powder Bed ◽  
Melt Pool ◽  
Bulk Nanocrystalline ◽  
Ribbon Structures ◽  
Nanocrystalline Ribbon

Lab scale additive manufacturing of Fe-Nd-B based powders was performed to realize bulk nanocrystalline Fe-Nd-B based permanent magnets. For fabrication a special inert gas process chamber for laser powder bed fusion was used. Inspired by the nanocrystalline ribbon structures, well-known from melt-spinning, the concept was successfully transferred to the additive manufactured parts. For example, for Nd16.5-Pr1.5-Zr2.6-Ti2.5-Co2.2-Fe65.9-B8.8 (excess rare earth (RE) = Nd, Pr; the amount of additives was chosen following Magnequench (MQ) powder composition) a maximum coercivity of µ0Hc = 1.16 T, remanence Jr = 0.58 T and maximum energy density of (BH)max = 62.3 kJ/m3 have been achieved. The most important prerequisite to develop nanocrystalline printed parts with good magnetic properties is to enable rapid solidification during selective laser melting. This is made possible by a shallow melt pool during laser melting. Melt pool depths as low as 20 to 40 µm have been achieved. The printed bulk nanocrystalline Fe-Nd-B based permanent magnets have the potential to realize magnets known so far as polymer bonded magnets without polymer.

Accelerating Large-Format Metal Additive Manufacturing: How Controls R&D Is Driving Speed, Scale, and Efficiency

2020 ◽  
Author(s):  
Brian T. Gibson ◽  
Paritosh Mhatre ◽  
Michael C. Borish ◽  
Justin L. West ◽  
Emma D. Betters ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Large Scale ◽  
Closed Loop ◽  
Size Control ◽  
Pool Size ◽  
Large Format ◽  
Layer Height ◽  
Melt Pool ◽  
The Impact ◽  
Melt Pool Size

Abstract This article highlights work at Oak Ridge National Laboratory’s Manufacturing Demonstration Facility to develop closed-loop, feedback control for laser-wire based Directed Energy Deposition, a form of metal Big Area Additive Manufacturing (m-BAAM), a process being developed in partnership with GKN Aerospace specifically for the production of Ti-6Al-4V pre-forms for aerospace components. A large-scale structural demonstrator component is presented as a case-study in which not just control, but the entire 3D printing workflow for m-BAAM is discussed in detail, including design principles for large-format metal AM, toolpath generation, parameter development, process control, and system operation, as well as post-print net-shape geometric analysis and finish machining. In terms of control, a multi-sensor approach has been utilized to measure both layer height and melt pool size, and multiple modes of closed-loop control have been developed to manipulate process parameters (laser power, print speed, deposition rate) to control these variables. Layer height control and melt pool size control have yielded excellent local (intralayer) and global (component-level) geometry control, and the impact of melt pool size control in particular on thermal gradients and material properties is the subject of continuing research. Further, these modes of control have allowed the process to advance to higher deposition rates (exceeding 7.5 lb/hr), larger parts (1-meter scale), shorter build times, and higher overall efficiency. The control modes are examined individually, highlighting their development, demonstration, and lessons learned, and it is shown how they operate concurrently to enable the printing of a large-scale, near net shape Ti-6Al-4V component.

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