Beyond the Toolpath: Site-Specific Melt Pool Size Control Enables Printing of Extra-Toolpath Geometry in Laser-Wire Directed Energy Deposition

A variety of techniques have been utilized in metal additive manufacturing (AM) for melt pool size management, including modeling and feed-forward approaches. In a few cases, closed-loop control has been demonstrated. In this research, closed-loop melt pool size control for large-scale, laser-wire based Directed Energy Deposition is demonstrated with a novel modification: site-specific changes to the controller set-point were commanded at trigger points, the locations of which were generated by the projection of a secondary geometry onto the primary 3D-printed component geometry. The present work shows that, through this technique, it is possible to print a specific geometry that occurs beyond the actual toolpath of the print head. This is denoted as an extra-toolpath geometry and is fundamentally different from other methods of generating component features in metal AM. A proof-of-principle experiment is presented in which a complex oak leaf geometry was embossed on an otherwise ordinary double-bead wall made from Ti-6Al-4V. The process is introduced and characterized primarily from a controls perspective with reports on the performance of the control system, the melt pool size response, and the resulting geometry. The implications of this capability, which extend beyond localized control of bead geometry to the potential mitigations of defects and functional grading of component properties, are discussed.

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Beyond the Toolpath: Site-Specific Melt Pool Size Control Enables Printing of Extra-Toolpath Geometry in Laser Wire-Based Directed Energy Deposition

Applied Sciences ◽

10.3390/app9204355 ◽

2019 ◽

Vol 9 (20) ◽

pp. 4355

Author(s):

Brian T. Gibson ◽

Bradley S. Richardson ◽

Tayler W. Sundermann ◽

Lonnie J. Love

Keyword(s):

Energy Deposition ◽

Closed Loop ◽

Size Control ◽

Pool Size ◽

Bead Geometry ◽

Site Specific ◽

Melt Pool ◽

Directed Energy Deposition ◽

Directed Energy ◽

Melt Pool Size

A variety of techniques have been utilized in metal additive manufacturing (AM) for melt pool size management, including modeling and feed-forward approaches. In a few cases, closed-loop control has been demonstrated. In this research, closed-loop melt pool size control for large-scale, laser wire-based directed energy deposition is demonstrated with a novel modification, i.e., site-specific changes to the controller setpoint were commanded at trigger points, the locations of which were generated by the projection of a secondary geometry onto the primary three-dimensional (3D) printed component geometry. The present work shows that, through this technique, it is possible to print a specific geometry that occurs beyond the actual toolpath of the print head. This is denoted as extra-toolpath geometry and is fundamentally different from other methods of generating component features in metal AM. A proof-of-principle experiment is presented in which a complex oak leaf geometry was embossed on an otherwise ordinary double-bead wall made from Ti-6Al-4V. The process is introduced and characterized primarily from a controls perspective with reports on the performance of the control system, the melt pool size response, and the resulting geometry. The implications of this capability, which extend beyond localized control of bead geometry to the potential mitigations of defects and functional grading of component properties, are discussed.

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Melt pool size control through multiple closed-loop modalities in laser-wire directed energy deposition of Ti-6Al-4V

Additive Manufacturing ◽

10.1016/j.addma.2019.100993 ◽

2020 ◽

Vol 32 ◽

pp. 100993 ◽

Cited By ~ 2

Author(s):

B.T. Gibson ◽

Y.K. Bandari ◽

B.S. Richardson ◽

W.C. Henry ◽

E.J. Vetland ◽

...

Keyword(s):

Energy Deposition ◽

Closed Loop ◽

Size Control ◽

Pool Size ◽

Melt Pool ◽

Directed Energy Deposition ◽

Directed Energy ◽

Melt Pool Size

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

Volume 2A: Advanced Manufacturing ◽

10.1115/imece2020-23322 ◽

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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Ultrasonic Frequency Effects on the Melt Pool Formation, Porosity, and Thermal-Dependent Property of Inconel 718 Fabricated by Ultrasonic Vibration-Assisted Directed Energy Deposition

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4048515 ◽

2020 ◽

Vol 143 (5) ◽

Author(s):

Fuda Ning ◽

Dayue Jiang ◽

Zhichao Liu ◽

Hui Wang ◽

Weilong Cong

Keyword(s):

Ultrasonic Vibration ◽

Inconel 718 ◽

Energy Deposition ◽

Pool Size ◽

Peak Temperature ◽

Ultrasonic Frequency ◽

Melt Pool ◽

Directed Energy ◽

Pool Formation ◽

Melt Pool Size

Abstract Ultrasonic vibration-assisted (UV-A) directed energy deposition (DED) has become a promising technology to improve the as-built quality and mechanical performance of metal parts. Ultrasonic frequency, a critical parameter of the ultrasonic vibration, can remarkably affect the ultrasonic vibration behaviors in assisting DED processes. However, leveraging varied ultrasonic frequencies in UV-A DED attracts little attention, and the effects of ultrasonic frequency have been thus overlooked. Linking ultrasonic frequency and part performance emphasizes the need for an understanding of the underlying thermodynamics in the melt pool due to the key role of thermal history in the DED process. In this work, we fabricated Inconel 718 (IN718) parts using the UV-A DED process under different levels of ultrasonic vibration frequency (including 0, 25 kHz, 33 kHz, and 41 kHz). For the first time, melt pool size, temperature distribution, and peak temperature within the melt pool, as well as the peak temperature fluctuation within a layer deposition, were studied. Porosity and thermal-dependent properties including grain size and microhardness were also investigated. The results indicated that the increase in ultrasonic frequency led to an increase in both melt pool size and peak temperature. Moreover, the lowest porosity was obtained at an ultrasonic frequency of 25 kHz, while grain refinement and microhardness enhancement were achieved at the highest frequency of 41 kHz. This investigation provides great insights into the link among ultrasonic frequency, melt pool formation, temperature field, porosity, and thermal-dependent properties in the UV-A DED-built IN718 parts.

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From mine to part: directed energy deposition of iron ore

Rapid Prototyping Journal ◽

10.1108/rpj-10-2020-0243 ◽

2021 ◽

Vol 27 (11) ◽

pp. 37-42

Author(s):

Himani Naesstroem ◽

Frank Brueckner ◽

Alexander F.H. Kaplan

Keyword(s):

Additive Manufacturing ◽

Laser Beam ◽

High Speed ◽

Iron Ore ◽

Energy Deposition ◽

Content Type ◽

Melt Pool ◽

Directed Energy Deposition ◽

Directed Energy ◽

Melt Pool Size

Purpose This paper aims to gain an understanding of the behaviour of iron ore when melted by a laser beam in a continuous manner. This fundamental knowledge is essential to further develop additive manufacturing routes such as production of low cost parts and in-situ reduction of the ore during processing. Design/methodology/approach Blown powder directed energy deposition was used as the processing method. The process was observed through high-speed imaging, and computed tomography was used to analyse the specimens. Findings The experimental trials give preliminary results showing potential for the processability of iron ore for additive manufacturing. A large and stable melt pool is formed in spite of the inhomogeneous material used. Single and multilayer tracks could be deposited. Although smooth and even on the surface, the single layer tracks displayed porosity. In case of multilayered tracks, delamination from the substrate material and deformation can be seen. High-speed videos of the process reveal various process phenomena such as melting of ore powder during feeding, cloud formation, melt pool size, melt flow and spatter formation. Originality/value Very little literature is available that studies the possible use of ore in additive manufacturing. Although the process studied here is not industrially useable as is, it is a step towards processing cheap unprocessed material with a laser beam.

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Closed loop control of melt pool width in robotized laser powder–directed energy deposition process

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-019-04195-y ◽

2019 ◽

Vol 104 (5-8) ◽

pp. 2887-2898 ◽

Cited By ~ 6

Author(s):

Meysam Akbari ◽

Radovan Kovacevic

Keyword(s):

Energy Deposition ◽

Closed Loop ◽

Deposition Process ◽

Closed Loop Control ◽

Loop Control ◽

Melt Pool ◽

Directed Energy Deposition ◽

Directed Energy

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Numerical investigation on heat transfer of melt pool and clad generation in directed energy deposition of stainless steel

International Journal of Thermal Sciences ◽

10.1016/j.ijthermalsci.2021.106954 ◽

2021 ◽

Vol 165 ◽

pp. 106954

Author(s):

Y.M. Zhang ◽

C.W.J. Lim ◽

C. Tang ◽

B. Li

Keyword(s):

Heat Transfer ◽

Stainless Steel ◽

Numerical Investigation ◽

Energy Deposition ◽

Melt Pool ◽

Directed Energy Deposition ◽

Directed Energy

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Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire

Metals ◽

10.3390/met11040634 ◽

2021 ◽

Vol 11 (4) ◽

pp. 634

Author(s):

Agnieszka Kisielewicz ◽

Karthikeyan Thalavai Pandian ◽

Daniel Sthen ◽

Petter Hagqvist ◽

Maria Asuncion Valiente Bermejo ◽

...

Keyword(s):

Heat Input ◽

Energy Deposition ◽

Fine Tuning ◽

Hot Wire ◽

Process Stability ◽

Electrical Signals ◽

Melt Pool ◽

Directed Energy Deposition ◽

Directed Energy ◽

The Stability

This study investigates the influence of resistive pre-heating of the feedstock wire (here called hot-wire) on the stability of laser-directed energy deposition of Duplex stainless steel. Data acquired online during depositions as well as metallographic investigations revealed the process characteristic and its stability window. The online data, such as electrical signals in the pre-heating circuit and images captured from side-view of the process interaction zone gave insight on the metal transfer between the molten wire and the melt pool. The results show that the characteristics of the process, like laser-wire and wire-melt pool interaction, vary depending on the level of the wire pre-heating. In addition, application of two independent energy sources, laser beam and electrical power, allows fine-tuning of the heat input and increases penetration depth, with little influence on the height and width of the beads. This allows for better process stability as well as elimination of lack of fusion defects. Electrical signals measured in the hot-wire circuit indicate the process stability such that the resistive pre-heating can be used for in-process monitoring. The conclusion is that the resistive pre-heating gives additional means for controlling the stability and the heat input of the laser-directed energy deposition.

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