Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

Please note that all times are shown in the time zone of the conference. The current conference time is: 29th Jan 2022, 06:04:09am CET

Only Sessions at Location/Venue 
Program for LiM 2021
Location: Room 2
ICM Second Floor 60
Date: Monday, 21/June/2021
3:30pm - 4:45pmJoint Session with CLEO/Europe: Welding and Cutting
Location: Room 2
Session Chair: Prof. Uwe Reisgen, RWTH Aachen University, Germany
Room 2 
3:30pm - 3:45pm

3-dimensional beam shaping for dynamic adjustment of focus position and intensity distribution for laser welding and cutting

Axel Jahn1, Dirk Dittrich1, Stephan Boerner1, Jens Standfuss1, Patrick Herwig1, Claudia Reinlein2

1Fraunhofer Institute for Material and Beam Technology IWS, Germany; 2Robust AO GmbH, Germany

Beam shaping, using highly dynamic beam oscillation, offers a high potential for the process control and thus the adaptation to specific process requirements. The realization of beam oscillation in 3 spatial directions opens up new possibilities for specific adjustment of the energy distribution in the melting zone and also creates prerequisites for high dynamic 3D welding and cutting.

A novel 3D optical system will be presented containing galvo-x/y-scanners combined with a new piezo-driven focus modulation (z-modul). This concept enables a synchronous high-frequency axis-control of the 3 spatial directions in a compact optics design.

In the lecture, construction concept and mode of operation of the 3D-system as well as achievable complex 3D energy distributions will be presented. Further, results of process investigations for welding Al alloys and 3D contours are shown and advantages in process stability and joint quality are derived.

3:45pm - 4:00pm

On-the-fly laser beam shaping with acousto-optofluidics

Martí Duocastella1,2, Alessandro Zunino2,3, Salvatore Surdo2

1Department of Applied Physics, Universitat de Barcelona, Spain; 2CHT, Istituto Italiano di Tecnologia, Italy; 3Department of Physics, University of Genoa, Italy


4:00pm - 4:15pm

Ultra-high quality through-transmission micro-welding and cutting of glass with ultrashort pulse lasers

Terence Hollister, Jim Bovatsek

MKS Spectra-Physics, United States of America

In recent years, glass has seen a renaissance of sorts, expanding into a wide variety of thicknesses, shapes, compositions and uses. Novel forms of glass are now widely used in microelectronics packaging, mobile device, automotive and bio-medical applications. Technologies to process glass have evolved as well, with ultrashort pulse (USP) laser technology becoming an important capability. Ultrashort pulse widths offer precision processing with controlled heat input that can minimize or even eliminate chipping and cracking. Combined with Bessel beam optics, high quality cutting of ultrathin glass (UTG) down to 100 µm thick can be realized. Operating at high pulse repetition frequencies, controlled thermal phenomena allows micro-welding of glass-to-glass and other materials. In this work, we demonstrate UTG cutting with roughness in the 10s of nm and ~1 m/s throughput as well as glass-glass and glass-aluminum micro-welding, with throughput approaching 500 mm/s and line widths of 10s of µm.

Date: Tuesday, 22/June/2021
10:00am - 11:00amAdditive Manufacturing: Directed Energy Deposition 1
Location: Room 2
Session Chair: Prof. Jean Pierre Bergmann, Technische Universität Ilmenau, Germany
Room 2 
10:00am - 10:15am

Development of laser-arc hybrid process for additive manufacturing of aluminum alloy and copper alloy

Dehua Liu, Shengnan Wu, Guangyi Ma, Fangyong Niu, Dongjiang Wu

Dalian University of Technology, Dalian, People's Republic of China

Laser-arc hybrid process was recently suggested as a feasible method for 3D printing the metal structural with high properties and low defects. To promote an understanding of the effect of laser on manufacturing process, this paper are performed to preparing aluminum alloy and cooper alloy using the integrating laser beam and tungsten inert gas (TIG) arc system. The microstructure evolution of aluminum alloy and copper alloy under different laser power are analyzed. Moreover, the elongation of the deposited aluminum alloy is improved on the higher tensile strength. The elongation of copper alloy sample is more than 40%. Relationship between the employed laser-arc manufacturing strateries and microstructure characteristics and mechanical properties are established. Laser-arc hybrid provides a new idea for additive manufacturing materials which are difficult to manufacture (high reflectivity, high thermal conductivity, et al.), and expand the application of laser additive manufacturing.

10:15am - 10:30am

Acoustic emissions of laser metal deposited NiTi structures

Julian Ulrich Weber1, Alexander Bauch1, Johannes Jahnke1, Claus Emmelmann2

1Fraunhofer IAPT, Hamburg, Germany; 2Institute of Laser and System Technologies (iLAS), Hamburg, Germany

Laser Metal Deposition (LMD) is an additive manufacturing process that enables the metal part production of complex near net-shape parts. Precise material deposition increases material efficiency and prevents the excessive use of costly materials. In a fully automated manufacturing process with minimized scrap production, these benefits are enabled by material specific process monitoring and parameter development.

Acoustic emissions were monitored for the LMD process of the costly shape memory alloy. Acoustic emission monitoring values were defined and evaluated regarding of NiTi structural defect formation. For the evaluation of defect formation, the degree of delamination for each specimen has been identified. Concurrent measurement of the oxygen content in the process chamber was carried out to correlate defects to the process atmosphere.

Distinct defect frequencies were detected for NiTi structures indicating delamination and cracks. The acquired data was used to design an LMD process control concept based on acoustic emission monitoring.

10:30am - 10:45am

Effect of atmosphere conditions on additive manufacturing of Ti4Al6V by coaxial W-DED-LB process

Eva Vaamonde, Rosa Arias, Pilar Rey, Iago Troncoso

AIMEN Technology Center, Spain

Additive Manufacturing is being a strategic tool for industrial applications even for large size structural parts where high deposition rates, as achieved by Directed Energy Deposition (DED) techniques based on wire deposition, are required. However, manufacturing of large components on reactive materials as titanium alloys requires specific atmosphere conditions to reach the specified properties on the deposited material. In this paper coaxial laser wire deposition (W-DED-LB) of titanium grade 5 alloy has been studied to achieve the highest deposition rate and process stability and the effect of protective conditions has been assessed. Three different configurations (local, inert chamber, local + inert chamber) were tested in order to bring a deep understanding of the influence of protective conditions on process stability, surface quality, metallurgy, hardness and oxygen content of deposited material.

10:45am - 11:00am

Processing of a low-alloyed case-hardening steel by means of DED-LB/M

Dominic Bartels1,2, Wolfgang Burgmayr1, Jonas Dauer1, Oliver Hentschel1,2, Michael Schmidt1,2

1Institute of Photonic Technologies (LPT), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Konrad-Zuse-Straße 3/5, 91052 Erlangen, Germany; 2Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 6, 91052 Erlangen, Germany

Low-alloyed steels are typically exposed to additional case-hardening post-processing to improve the mechanical properties in the case area of the material for increased hardness and wear resistance. Another possibility for improving these material properties is provided by in-situ alloying using laser-based directed energy deposition of metals (DED-LB/M). However, this requires basic understanding of the mechanisms when processing the base material. Within this work, different processing strategies for defect-free fabrication of a low-alloyed case-hardening steel are presented. This includes the correlation of geometrical properties and internal defects like pores or cracks with the applied process parameters. It is found that track geometry and diffusion zone are highly dependent on laser power and scanning speed. Additionally, hardness measurements are performed for analyzing the influence of different processing strategies on material properties. It is found that the corresponding material hardness varies inside a layer and that a hardness gradient is formed.

11:15am - 12:30pmAdditive Manufacturing: Systems Engineering
Location: Room 2
Session Chair: Prof. Peter Loosen, Fraunhofer Institute for Laser Technology ILT, Germany
Room 2 
11:15am - 11:30am

RECILS: high resolution and high-speed SLA 3D printer using a plane building platform and a cylindrical glass window

Kentaro Soeda, Hirosuke Suzuki, Shuichi Yokobori, Kuniaki Konishi, Hiroharu Tamaru, Norikatsu Mio, Makoto Kuwata-Gonokami, Junji Yumoto

The University of Tokyo, Japan

We propose a novel stereolithography 3D printer configuration, called RECILS, achieved by combining a plane building platform (BP) and a cylindrical glass window (CW). The BP is deployed above the sidewall of the CW placed horizontally with a gap of 10 micrometer to 40 micrometer. UV curable resin is supplied into the gap and cured by the UV laser light passing through the CW. The UV laser light with a spot size of 10 micrometer is scanned lineally along the gap by a polygon mirror. The UV light is modulated by the STL data, and the BP is translated in a direction perpendicular to the laser-scan direction, synchronized exactly with the laser scan. This operation is equivalent to a raster scan. The subsequent layers are formed below the previous layer and accurate 3D-modeling is enabled. Additionally, the use of a CW eliminates peeling process and greatly reduces the manufacturing time.

11:30am - 11:45am

Additive manufacturing & the need to get the laser beam right

Nicolas Meunier

MKS Instruments - Ophir Brand, Germany

Is additive manufacturing ready for mass-production? The answer really boils down to reproducibility. When it comes to selective laser melting, the constancy of the laser parameters is of great importance. Both, the manufacturers of the laser systems and the users thereof should be aware of the quality of the focused beam. As measuring a (high power) laser beam in the limited space of a production chamber is a challenge, new measurement technology had to be developed. Today, different technologies are available to measure the focused beam quickly and cost-effectively within the process.

Nicolas Meunier, Business Development Manager High Power und Automotive Products Ophir, introduces key measurement techniques, outlines their impact on the way to mass production and explains how to achieve reproducibility in laser-based additive manufacturing.

11:45am - 12:00pm

Arrangement for the benchmarking of in situ process monitoring of topographical process signatures within the laser powder bed fusion process

Karen Schwarzkopf1,2, Eric Eschner1,2, Michael Schmidt1,2

1Institute of Photonic Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Konrad-Zuse-Str. 3/5, 91052 Erlangen, Germany; 2Graduate School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 6, 91052 Erlangen, Germany

Additive manufacturing technologies such as powder bed fusion of metals by a laser beam (PBF-LB/M) offer great potential for production of geometrically complex components. Yet, physical defect mechanisms lack fundamental understanding. Crucial for broadening process knowledge is in-situ monitoring of observable process signatures related to the powder heating, melting, and solidification processes. Whereas the geometry and temperature profile of the melt pool have been intensively examined, little is known about topographical process signatures occurring in PBF-LB/M. In this paper we (i) identify topographical process signatures within PBF-LB/M, (ii) relate them to physical defect mechanisms and (iii) evaluate monitoring approaches proposed in literature to access them. Based on that, we present an experimental set-up with high spatial and temporal resolution consisting of a high-speed imaging (HSI) camera and a low coherence imaging (LCI) system. The coaxial arrangement enables simultaneous observation of the melt pool behavior and topographical process features within PBF‑LB/M.

12:00pm - 12:15pm

Spatially resolved melt pool monitoring for process characterization in laser powder bed fusion (LPBF)

Dieter Tyralla, Peer Woizeschke, Thomas Seefeld

BIAS - Bremer Institut für angewandte Strahltechnik GmbH, Germany

Laser powder bed fusion (LPBF) is a frequently used manufacturing process for complex shaped geometries, e.g. bionic structures. The part quality often depends not only on process parameters but also on geometrically induced changes in thermal conditions. Thus, already identified parameters may need to be adjusted to the geometry. Here, a temperature measurement provides information about the current process state due to its recognition of heat input, accumulation and flux during build-up and thus assists the parameter development.

The present work applies a spatially resolved temperature measurement for process monitoring in LPBF using 2-channel-pyrometry. A lateral resolution of 10 µm is achieved within the complete build-up volume of 250x250x250 mm³ by the coaxial integration of the pyrometric camera system into the beam path of a LPBF machine. The melt pool area was identified as a suitable indicator which enables the prediction of part density during build-up process.

12:15pm - 12:30pm

The final steps towards guaranteed quality and first-time-right - 3D printing with powder and wire enabled by OCT sensor technology

Markus Kogel-Hollacher1, Frédéric Adam1, Christian Staudenmaier1, Rüdiger Moser1, Steffen Boley2

1Precitec GmbH & Co. KG, Germany; 2Institut für Strahlwerkzeuge (IFSW), University of Stuttgart, Germany

Today’s manufacturing processes, especially 3D printing with powder or wire, presuppose Industry 4.0 solutions, which require supervision of every single production step. Transforming machine elements into intelligent cyber physical systems involves the integration of smart sensors for condition and process monitoring. As photonic solutions are by nature contact free processes it would be advantageous if the sensor is based on light as well, if the light could be coupled into the beam path of the processing laser and if the sensor can really measure surface topography in micrometer resolution. In this case the production process can be directly connected to the CAD data set, the process could be controlled to eliminate geometrical deviations to the desired geometry and first-time-right is not a pious hope anymore. We talk about controlled individualized lot size 1 production based on OCT sensor technology.

1:30pm - 2:30pmAdditive Manufacturing: Innovations for Powderbed Fusion
Location: Room 2
Session Chair: Dr. Dirk Herzog, Hamburg University of Technology, Germany
Room 2 
1:30pm - 2:00pm

Invited Talk: Advances on the Laser Powder Bed Fusion of Structural Materials: microstructure, processing and material strength

Sergio Amancio

Institute of Materials Science, Joining and Forming, Graz University of Technology, Austria


2:00pm - 2:15pm

Laser-based powder bed fusion with 16 kW

Artur Leis1,2, Stefan Bechler1, Rudolf Weber1, Thomas Graf1

1Institut für Strahlwerkzeuge (IFSW), University of Stuttgart, Germany; 2Graduate School of Excellence advanced Manufacturing Engineering (GSaME), University of Stuttgart, Germany

Laser-based Powder Bed Fusion (LPBF) is typically performed at laser powers between 500-1000W, and laser beam diameters between 50-500µm. The generation of parts therefore requires a significant amount of time because the average power basically defines the productivity. To reduce the processing time, the laser power was set to 16kW and the laser beam diameter was adjusted to produce continuous melt beads. Additively manufactured samples of AlSi10Mg were used for the high-power experiments. The melting process was recorded with a high-speed camera. The generated beads were analysed metallographically to determine the extent and shape of the molten region, the crystallographic structure and the porosity. It was found that it was possible to generate continuous melt beads with laser beam diameters between 2.5-3.8mm at feed rates between 0.5-1.5m/s with a laser power of 16kW, at the expense of hydrogen-induced porosity. In the talk, the results will be presented and discussed.

2:15pm - 2:30pm

Manufacturing knowledge: model instead of experience, a big step towards reproducibility and first-time-right in the production of complex component geometries using PBF-LB/M

Hannes Korn1, Stefan Holtzhausen2, Claudia Ortmann3, Felix Gebhardt1, Ralph Stelzer2, Welf-Guntram Drossel1

1Fraunhofer Institute for Machine Tools and Forming Technology IWU, Germany; 2Technical University of Dresden, Institute of Machine Elements and Machine Design, Germany; 3Mathys Orthopädie GmbH, Germany

The cost structure and geometry freedom of laser powder bed fusion (PBF-LB/M) holds great potential for lightweight-capabilities, customization and on-demand manufacturing of metal parts. Obstacles currently exist in first-time-right manufacturing and reliable reproducibility under changing process conditions. Reasons are the many setting variables (laser-parameters, process-parameters, scan-strategy) and disturbance variables (powder-batch, operator, ambient conditions), which have a difficult to quantify influence on the quality characteristics of the component (warpage, surface-roughness, porosity).

Compared to the so far widespread experience-based parameterization of the process, statistical modeling has great potential for describing and understanding the effects of the setting- and disturbance variables on the quality characteristics quantitatively. The influence of scan-strategy and laser-parameters on the warpage and surfaces of PBF-LB/M-components is evaluated on cantilever-like bridge specimens according to an optimized experimental plan. The relation between setting variables and quality characteristics is quanified in a linear model approach afterwards and its predictive power is evaluated.

2:45pm - 4:00pmAdditive Manufacturing: Innovations
Location: Room 2
Session Chair: Prof. Michael F. Zaeh, Technical University of Munich, Germany
Room 2 
2:45pm - 3:00pm

Fabrication strategies with fixed diffractive optical elements for high speed two-photon polymerization

Francisco Gontad, Sara M. Vidal, Nerea Otero-Ramudo, Pablo Romero-Romero

AIMEN Technology Centre, O Porriño, ES36418, Pontevedra, Spain

The benefits of Two-Photon Polymerization (TPP) are well known for the fabrication of 3D structures with micron and even submicron sizes. However, the fabrication time of these structures is still far from being competitive with other techniques. In this work, the use of fixed Diffractive Optical Elements (DOEs) is presented as a valid approach to boost the fabrication speed of TPP. In this way, the fabrication strategy for different 2.5D and 3D microstructures, taking advantage of the use of DOEs with different optical configurations, is presented and discussed. The results of this study suggest that the fabrication speed can be increased up to 20 times through the correct combination of DOE and path planning, without the need of an excessive average power.

3:00pm - 3:15pm

Process strategies on laser-based melting of glass powder

Thomas Schmidt1, Susanne Kasch1, Fabian Eichler2, Laura Katharina Thurn2

1ifw Jena GmbH, Germany; 2Fachhochschule Aachen, Germany

This paper presents the laser-based powder bed fusion (L-PBF) using various glass powders (borosilicate, quartz glass). Compared to metals, these require adapted process strategies. First, the glass powders were characterized by means of various methods with regard to their material properties and their processability in the powder bed. This was followed by investigations of the melting behavior of the glass powders with different laser wavelengths (10.6µm, 1070nm). In particular, the experimental setup of a CO2 laser was adapted for the processing of glass powder. An experimental setup with integrated coaxial temperature measurement/control and an inductively heatable build platform was created. This allowed the L-PBF process to be carried out at the transformation temperature of the glasses. Furthermore, the component’s material quality was analyzed on three-dimensional test specimen with regard to porosity, roughness, density and component accuracy in order to evaluate the developed L-PBF parameters and to open up possible applications.

3:15pm - 3:30pm

Comparison of different density measurement techniques for laser assisted powder bed fusion

Lisa Schade1, Gabor Matthäus1, Hagen Kohl1, Burak Yürekli1, Tobias Ullsperger1, Brian Seyfarth1, Stefan Nolte1,2

1Friedrich-Schiller-Universität Jena, Germany; 2Fraunhofer Institute for Applied Optics and Precision Engineering, IOF Jena, Germany

One of the major quality control criteria for additively manufactured parts is the density achieved. Besides fundamental properties like microstructure, residual strain or impurities, the density fundamentally defines how the final product matches the intended material properties. In general, mostly surface inspections of randomly prepared cross sections are undertaken. On the one hand side, this approach delivers important information regarding the morphology and distribution of pores, however, on the other hand side, this characterization only considers a small fraction of the entire sample volume and therefore cannot reflect the true density without a significant level of uncertainty. In this work, we investigate three different measurement techniques, light microscopy, x-ray tomography and pycnometry with a focus on their advantages and disadvantages. The results show significant differences of the obtained density values with deviations in the range of several percent depending on the underlying material.

3:30pm - 3:45pm

Developing process parameters through CFD simulations

Pareekshith Allu1, Frieder Semler2

1Flow Science Inc., United States of America; 2Flow Science Deutschland GmbH, Germany

Laser-material interaction is complex, and to accurately simulate it requires implementing the physics models that are relevant at these temporal and spatial scales. Process parameters such as laser power, scanning velocity, geometric scanning path, pre-heating temperature and powder size distribution influence the melt pool dynamics, which controls the stability of the additive manufacturing process. In this presentation, we will look at underlying mechanisms behind the formation of defects such as balling, porosity and spatter using computational thermal-fluid dynamics models built in FLOW-3D AM. While low energy densities can lead to lack of fusion defects, high energy densities result in strong recoil pressure and unstable keyholes that can lead to the formation of porosity and spatter. In addition to helping with process parameter development for both LPBF and DED processes, such models also output thermal gradient and cooling rate data that can be used to predict microstructure evolution.

3:45pm - 4:00pm

Laser-induced forward transfer (LIFT) of micro-LED devices

Alberto Piqué, Ray Auyeung, Kristin Charipar, Heungsoo Kim, Michael Malito, Nicholas Charipar

U.S. Naval Research Laboratory, United States of America

We explore the application of laser-induced forward transfer (LIFT) techniques for laser printing of micro-LED devices. LIFT enables printing of functional materials ranging from silver nano-inks to working devices such as bare-die semiconductor components over a wide range of surfaces in an additive fashion achieving high transfer throughputs. LIFT is a non-mechanical, non-contact device transfer process operating beyond the size limits of pick-and-place methods. That is, LIFT offers a ‘lase-and-place’ approach for transferring the building blocks required for the fabrication of a wide range of functional circuits. LIFT techniques are being investigated by the U.S. Naval Research Laboratory to print micro-LED devices for applications in hybrid electronics. Examples of structures and circuits made by LIFT and their role in the development of next generation laser micro processing techniques will be presented.

This work was funded by the Office of Naval Research (ONR) through the Naval Research Laboratory Basic Research Program.

Date: Wednesday, 23/June/2021
10:00am - 11:00amAdditive Manufacturing: Powderbed, Metal 1
Location: Room 2
Session Chair: Dr. Peer Woizeschke, BIAS – Bremer Institut für angewandte Strahltechnik GmbH, Germany
Room 2 
10:00am - 10:15am

Investigation of Kovar in PBF-LB/M

Arvid Abel1, Jakob Pufal1, Vitaly Rymanov2, Christian Hoff1, Jörg Hermsdorf1, Stefan Kaierle1, Andreas Stöhr2,3, Sumer Maklouf3, Jörg Lackmann3

1Laser Zentrum Hannover e.V., Germany; 2Microwave Photonics GmbH, Germany; 3Universität Duisburg-Essen, Zentrum für Halbleitertechnik und Optoelektronik, Germany

The iron-nickel-cobalt alloy Kovar is highly desirable in glass-to-metal hybrid components, e.g., hermetic seals, or as packaging material in high-frequency microsystems due to its thermal expansion coefficient similar to borosilicate glass. Hitherto, the processability of Kovar in additive manufacturing has only been insufficiently investigated, leaving the potential of this material for functional integrated components unused. This paper describes the processing in PBF-LB/M and the understanding of the process parameters to achieve a relative density over 99.9 % in test specimens, large volumes, and complex structures. The investigated factors were laser power, scanning speed, and hatch distance. The initial experiments were done as full factorial designs. Subsequent investigations were done within the design of experiments to develop an empirical process model for the fabrication of Kovar in the PBF-LB/M. The best results were fabricated with volumetric energy densities between 200 to 350 to achieve a maximum density of 99.94 %.

10:15am - 10:30am

Machine-comprehensive study of comparability and reproducibility for laser powder bed fusion of corrosion resistant steel 316L/1.4404

Florian Bittner1, Bernhard Müller1, Maximilian Zinke2, Aitor Echaniz3, Sebastian Matthes4, Burghardt Klöden5, Christian Kolbe6

1Fraunhofer IWU - Institute for Machine Tools and Forming Technology; 2AM metals GmbH; 3Robert Bosch GmbH; 4ifw Jena - Günter Köhler-Institut für Fügetechnik und Werkstoffprüfung; 5Fraunhofer IFAM - Institute for Manufacturing Technology and Advanced Materials, Location Dresden; 6FKT GmbH

Additive Manufacturing of metallic components by laser powder bed fusion (LPBF) earns increasingly importance for industrial applications. However, for further industrial penetration different challenges have to be overcome. The most urging challenge is the warranty and control of a constant high quality, which includes machine-comprehensive comparability of components goodness. Important factors are the respective machine concept, used powder as well as respective processing parameters.

The results of a standard VDI 3405-2 based round robin test for steel 316L (1.4404) are discussed, at which five partners with different machines participated. The implementation is not based on ideal conditions, but addresses the respective individual best practise. Thereby, the differences between included machine concepts and scattering within a manufacturing order are discussed. With this, the existing gap of standardisation of properties for LPBF of the well-established material 316L/1.4404 shall be closed analogue to a series of other materials within the VDI-standard family 3405.

10:30am - 10:45am

Oxide dispersion strengthened steel manufactured by laser powder bed fusion and directed energy deposition

Carlos Doñate-Buendia1,2, Philipp Kürnsteiner3,4, Markus Benjamin Wilms5, Baptiste Gault3,6, Bilal Gökce1,2

1Department of Materials Science and Additive Manufacturing, University of Wuppertal, 42119 Wuppertal, Germany; 2Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany; 3Department Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany; 4Christian Doppler Laboratory for Nanoscale Phase Transformations, Center for Surface and Nanoanalytics (ZONA), Johannes Kepler UniversityLinz, Altenberger Straße 69, 4040 Linz, Austria; 5Fraunhofer Institute for Laser Technology, 52074 Aachen, Germany; 6Department of Materials, Royal School of Mines, Imperial College, Exhibition Road, London, SW7 2AZ, UK

Additive manufacturing technologies appear ideal for the generation of custom geometries and parts. In the context of specific applications such as high-temperature industrial processes like gas turbines or furnaces, the development of parts with enhanced high-temperature strength and oxidation resistance is highly desired. Oxide dispersion strengthened (ODS) steels are considered as suitable materials for such high temperature application. To assess the effect of the processing technique on the manufacturing of ODS steels and its properties, an Fe-Cr based steel powder decorated with a 0.08 wt% of laser generated Y2O3 nanoparticles is processed by laser powder bed fusion (LPBF) and directed energy deposition (DED). We show that the produced specimens show superior mechanical properties at 600ºC compared to the reference part built without nanoparticle-addition. The enhanced mechanical properties are explained by the microstructure and nanoparticle dispersion in the generated ODS steels and confirmed by melt pool simulations.

11:15am - 12:30pmAdditive Manufacturing: Powderbed, Metal 2
Location: Room 2
Session Chair: Dr. Peer Woizeschke, BIAS – Bremer Institut für angewandte Strahltechnik GmbH, Germany
Room 2 
11:15am - 11:45am

Invited Talk: Insight into fatigue behaviour of additively manufactured alloys: results of the DREAM project

Elena Bassoli

Department of Engineering „Enzo Ferrari“, Univ. Modena e Reggio Emilia, Italy


11:45am - 12:00pm

3D printing of Al-Li with increased Li content using laser assisted powder bed fusion

Burak Yürekli1, Dongmei Liu2, Tobias Ullsperger1, Hagen Kohl1, Lisa Schade1, Gabor Matthäus1, Markus Rettenmayr2, Stefan Nolte1,3

1Institute of Applied Physics, Friedrich Schiller University Jena, Germany; 2Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Germany; 3Fraunhofer Institute for Applied Optics and Precision Engineering, IOF Jena, Germany

Based on the extremely low atomic mass of Li, the binary alloy Al-Li holds high potential for future light-weight alloys. In particular, the elastic modulus significantly increases with rising Li content, offering the potential of extremely high stiffness as compared to conventional Al alloys. However, due to the limited solubility of Li accompanied by the formation of brittle δ-AlLi phase during solidification, the maximum Li content is generally limited to about 2 wt. %. Here we present laser assisted 3D printing using Al-Li with an increased Li content of 4 wt. %. The process is based on custom-made Al-Li powder, which is characterized in terms of powder particle size, density, absorption, and thermal conductivity. In contrast to common approaches, here, ultrashort laser pulses are used for the melting process, delivering 3D printed parts with a drastically reduced fraction δ-AlLi phase due to the increased solidification rates of the melt pool.

12:00pm - 12:15pm

Adjusting the surface roughness of WE43 components manufactured by laser-based powder bed fusion

Tjorben Griemsmann, Niclas Söhnholz, Christian Hoff, Jörg Hermsdorf, Stefan Kaierle

Laser Zentrum Hannover e.V., Germany

The outstanding characteristics of magnesium alloys make them promising materials for biomedical or lightweight construction applications, especially in combination with the advantages of laser-based powder bed fusion. While most research in this field focusses porosity and microstructural properties, the surface quality is left out. Because the surface is an important factor for corrosion and notch effects, this work addresses the adjustment of the surface roughness from parts made out of a WE43 alloy. Using design of experiments contour scan trials are carried out for vertical and down skin surfaces. As a result, the roughness of vertical surfaces is reduced from approximately 27.1 µm (Ra) and 172.2 µm (Rz) without contour scans to 10.9 µm and 87.4 µm with contour scans. The applicability of the contour parameters is approved by cross sections to investigate the porosity of the contour volume interface and a topology optimized gear housing is manufactured for validation.

12:15pm - 12:30pm

Influence of process-relevant parameters and heat treatments on the microstructure and resulting mechanical behavior of additively manufactured AlSi10Mg via laser powder bed fusion

Andreas Kempf1, Leonardo Agudo Jácome2, Kai Hilgenberg3

1Volkswagen AG, Werkstofftechnik, 38436 Wolfsburg, Deutschland; 2Bundesanstalt für Materialforschung und -prüfung (BAM), Division 5.1 – Materialographie, Fraktographie und Alterung technischer Werkstoffe, 12205 Berlin, Deutschland; 3Bundesanstalt für Materialforschung und -prüfung (BAM), Division 9.6 – Additive manufacturing of metallic components, 12205 Berlin, Deutschland

Within the group of additive manufacturing (AM) technologies for metals, laser powder bed fusion (L-PBF) has a leading position. Nevertheless, reproducibility of part properties has not reached sufficient maturity hindering the use for industrial applications especially for safety-relevant components. This article presents the results of various experimental tests performed with the aluminium alloy AlSi10Mg identifying reasons for the high deviations in mechanical properties. Herein, it is discussed how microstructure is influenced by different process parameters (laser power, scanning speed, energy density, building time) and how it can be adjusted by suitable post process heat treatments. The impact of resulting changes in microstructure on the mechanical behavior is shown by quasistatic and cyclic tests considering samples manufactured with different L-PBF machines.

1:30pm - 2:30pmAdditive Manufacturing: Directed Energy Deposition 2
Location: Room 2
Session Chair: Prof. Stephan Barcikowski, University of Duisburg-Essen, Chemical Technology, Germany
Room 2 
1:30pm - 1:45pm

In-situ clad geometry measurement in wire laser metal deposition process

Iker Garmendia, Jon Flores, Carlos Soriano, Mikel Madarieta

Tekniker, Spain

Wire Laser Metal Deposition (w-LMD) is a promising technique that could generate significant cost reductions. However, process control still needs to be developed to ensure product quality. Due to the high temperature of the melt pool and the resulting light radiation, current commercial equipment can only measure the geometry of the clad after the process or between the deposition of different layers, which affects the heating and cooling cycles of the part and the manufacturing time. In this work, a measurement system based on a side mounted vision camera and laser light projection is developed, which allows an in-situ measurement of the clad geometry data. This enables to know the nozzle-to-part distance, the surface where the successive layers are deposited, or bead parameters related to the quality of the deposition.

1:45pm - 2:00pm

Structure-borne acoustic process monitoring of laser metal deposition

Irene Buchbender, Christian Hoff, Jörg Hermsdorf, Volker Wesling, Stefan Kaierle

Laser Zentrum Hannover e.V., Germany

Acoustic emissions have been used as a means for process monitoring and non-destructive testing in welding to determine process characteristics, detect anomalies and infer the quality of the welded part. While air-borne noise has been studied extensively, research on the application of body-borne sound in the process monitoring of laser metal deposition remains limited. This paper examines the use of structure-borne sound for in-process monitoring of the deposition of the Nickel-based Superalloy CMSX-4. Due to the low weldability of the material and its susceptibility to hot-cracking, there arises a need for an in-process, non-destructive method for monitoring cracking. A high-frequency-impulse-measuring device (QASS GmbH) up to 50 MHz was attached to the substrate mount. The frequency data of the signal over time was evaluated by analysing the Short-Time Fourier transform (STFT) of the raw acoustic data, the acoustic characteristics of the process were determined, acceptable thresholds set and cracking detected.

2:00pm - 2:15pm

Studies on the direction-independent temperature measurement of a coaxial laser metal deposition process with wire

Avelino Zapata, Christian J. Bernauer, Melanie Hell, Michael F. Zaeh

Technical University of Munich, Germany

Among the Directed Energy Deposition (DED) processes, the Laser Metal Deposition with wire (LMD-w) combines the advantages of a high precision and a high deposition rate. Recently, optical systems have been developed that form an annular laser spot, facilitating a direction-independent process. However, when a pyrometer is coupled to the optical system, also the measurement spot assumes the form of a ring. This work studies the inline temperature signal of a pyrometer with a ring-shaped measurement spot for the LMD-w process. High-speed videos are used to interpret the signals based on process observations. The two modalities of a single and a two-color measurement are compared regarding their reliability. The measurement setup is varied to study the influence of different process conditions on the signal. At last, a configuration is identified that allows a valid measurement. The reliable inline temperature measurement opens the opportunity to monitor and control the process.

2:15pm - 2:30pm

Process development for laser hot-wire deposition welding with high-carbon cladding material AISI 52100

Laura Budde, Marius Lammers, Jörg Hermsdorf, Stefan Kaierle, Ludger Overmeyer

Laser Zentrum Hannover e.V., Hollerithallee 8, D-30419 Hannover, Germany

An increase in wear resistance and thus an increase in service life is of great importance for many components. The production of hybrid components with high-carbon steel as cladding material offers the possibility of achieving these goals. However, materials with a carbon equivalent of more than 0.65 are considered difficult to weld due to their tendency to crack. In this study, a laser hot-wire deposition welding process with bearing steel AISI 52100 as cladding material is used to investigate the influence of laser power, wire feed speed, scanning speed, overlap ratio and wire preheating as well as interactions of these parameters on process stability, the formation of cracks and pores, the cladding waviness and the dilution. Layers of eight adjacent weld seams are welded onto an austenitic stainless steel. A stable process is observed for most parameter combinations except for samples with low wire feed speed and major wire preheating.

2:45pm - 4:00pmAdditive Manufacturing: Non-metal
Location: Room 2
Session Chair: Leander Schmidt, Technische Universität Ilmenau, Germany
Room 2 
2:45pm - 3:00pm

Additive manufacturing of magnetic parts by laser powder bed fusion of iron oxide nanoadditivated polyamide powders

Carlos Doñate-Buendia1,2, Alexander Sommereyns3,4, Jochen Schmidt5, Michael Schmidt3,4, Stephan Barcikowski2, Bilal Gökce1,2

1Department of Materials Science and Additive Manufacturing, University of Wuppertal, 42119 Wuppertal, Germany; 2Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Universitaetsstrasse 7, 45141 Essen, Germany; 3Institute of Photonic Technologies (LPT), Friedrich-Alexander Universität Erlangen-Nürnberg, Konrad-Zuse-Str. 3-5, 91052 Erlangen, Germany; 4Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander Universität Erlangen-Nürnberg, Germany; 5Institute of Particle Technology (LFG), Friedrich-Alexander Universität Erlangen-Nürnberg, Cauerstr. 4, 91058 Erlangen, Germany

Laser powder bed fusion allows the processing of polymer powders with design freedom, achieving highly complex geometry required for medical and aerospace applications. The characteristics of the generated parts and processability depends on the initial polymer powder properties. A route to achieve a controlled modification of the polymer powders and adapt the properties of the final parts to the desired application is the nanoadditivation of the powders. The generation of superparamagnetic iron oxide nanoparticles by laser fragmentation and supporting on polyamide (PA12) is shown to transfer the magnetic response to the resulting nanoadditivated powder even when the nanoparticle loading is only 0.1 wt%. The characterization of the as built parts confirms that the saturation magnetization and structure of the iron oxide nanoparticles are not influenced by laser powder bed fusion processing, proving the successful transfer of the initial nanoparticle properties to the 3D-printed part.

3:00pm - 3:15pm

Polymer powders with enhanced absorption in the NIR for laser powder bed fusion with diode lasers

Michael Willeke, Carlos Donate-Buendia, Tim Hupfeld, Stephan Barcikowski, Bilal Gökce

Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Universitaetsstrasse 7, 45141 Essen, Germany

Additive manufacturing techniques represent an ideal manufacturing process for series components, for example in the automotive industry when good mechanical properties and precision are needed. In that sense, Laser Powder Bed Fusion (LPBF) is a manufacturing technique already employed in several applications where polymer parts with complex geometries are required. However, since the employed polymer powders exhibit a low absorption in the visible and NIR wavelength range, the laser sources employed in polymer LPBF are limited.

To address this difficulty, the addition of near-infrared absorbing LaB6 nanoparticles is proposed and tested on the most employed polymer powder for LPBF, i.e. polyamide 12 (PA12). The nanoparticles are generated by laser ablation in liquid and homogeneously dispersed on the polymer surface by dielectrophoretic deposition. The resulting nanoadditivated polymer powder exhibits an absorption maximum at 800 nm, suitable for its processability by LPBF with NIR laser sources.

3:15pm - 3:30pm

Powder bed fusion of ultra-high molecular weight polyethylene using ultra-short laser pulses

Tobias Ullsperger1, Yannick Wencke2, Burak Yürekli1, Gabor Matthäus1, Gerrit Luinstra2, Stefan Nolte1,3

1Institute of Applied Physics, Friedrich-Schiller University Jena; 2Institute for Technical and Macromolecular Chemistry, University of Hamburg; 3Fraunhofer Institute for Applied Optics and Precision Engineering, IOF Jena

Laser powder bed fusion (L-PBF) of ultra-high molecular weight polyethylene (UHMWPE) is a new approach to fabricate complex components for medical implants. CO2 laser radiation is the method of choice to selectively heat up the powder particles above the melting point. Although previous studies have shown the feasibility to fuse UHMWPE, the produced sprecimen lack of warping and material degradation. Moreover the achievable geometrical resolution is limited by the large spot size of several 100 µm.

In this paper, we demonstrate an alternative approach for L-PBF of UHMWPE by using 500 fs laser pulses at a wavelength of 1030 nm. The peak intensity of several 100 MW/cm2 allows for an efficient multi-photon absorption in the transparent polymer. Thus, it was possible to completely melt the powder with less degradation. Furthermore, the achieved tensile strength of 4 MPa is 60 % higher in comparison to produced samples using conventional CO2 L-PBF.

3:30pm - 3:45pm

Experimental investigations on lateral path overlay and the degree of mixing of additively manufactured soda-lime and borosilicate glass structures

Fabian Fröhlich, Jörg Hildebrand, Jean Pierre Bergmann

Technische Universität Ilmenau, Production Technology Group, Germany

In this scientific paper, the influence of the lateral distance between the welding lines on the geometric dimensions and the degree of mixing of the additively manufactured glass structure is investigated. Initial experimental investigations have shown that the additive manufacturing of quartz, soda-lime and borosilicate glass is possible when material- and process-specific process parameters are taken into account. Using a CO2-laser, the silicate glasses and the rod-based additive material are melted. For this experimental investigation, the ratio between welding and feeding speed of the filler material, as well as the laser power, is kept constant. The fabricated structures are subjected to post heat treatment to relieve thermally induced stresses and are examined with photoelasticity. Geometrical dimensions, such as layer height, width and bond angle, as well as the degree of mixing are quantified after materialogprahy sample preparation. The knowledge is used to optimise near-net-shape additive manufacturing of glass components.

3:45pm - 4:00pm

Manufacturing of fused silica volume parts by means of laser glass deposition

Katharina Rettschlag1,2, Simon Stieß1, Peter Jäschke1, Stefan Kaierle1, Roland Lachmayer1,2

1Laser Zentrum Hannover e.V., Germany; 2Institute for product development, Leibniz University Hannover, Germany

Additive manufacturing (AM) of polymers and metals is already established in the industry. Materials such as glass create significant challenges based on their material properties. Especially mechanical and thermal properties as well as the viscosity behavior are difficult to handle. So far, only few specialized glass AM processes exist and are established in research and development.

The Laser Glass Deposition (LGD) process offers the possibility to deposit glass fibers without using binder materials. For the application area of optical components, manufactured parts must fulfill high requirements for transparency, surface quality, material purity and homogeneity of the material. Investigations on the printing of individual single-layer quartz glass structures have already been carried out with the LGD process. Within this article the influence of laser power, axis speed and fiber feeding speed on the deposition characteristics is investigated shortly. Subsequently, a multilayer deposition is investigated to manufacture solids with an optical transparency.

Date: Thursday, 24/June/2021
10:00am - 11:00amAdditive Manufacturing: Directed Energy Deposition 3
Location: Room 2
Session Chair: Nicole Emminghaus, Laser Zentrum Hannover e.V., Germany
Room 2 
10:00am - 10:15am

Analysis and recycling of bronze grinding waste to produce maritime components using directed energy deposition

Vinzenz Müller1, Angelina Marko1, Tobias Kruse2, Max Biegler1, Michael Rethmeier1,3

1Fraunhofer Institute for Production Systems and Design Technology IPK, Germany; 2Mecklenburger Metallguss GmbH, Germany; 3Bundesanstalt für Materialforschung und -prüfung (BAM), Germany

Additive manufacturing promises a high potential for the maritime sector. Directed Energy Deposition (DED) in particular offers the opportunity to produce large-volume maritime components like propeller hubs or blades without the need of a costly casting process. The post processing of such components usually generates a large amount of aluminum bronze grinding waste. The aim of the presented project is to develop a sustainable circular AM process chain for maritime components by recycling aluminum bronze grinding waste to be used as raw material to manufacture ship propellers with a laser-powder DED process. In the present paper, the main challenges and promising measures and methods to recycle metallic grinding waste are shown. Two types of grinding waste are investigated using a CamSizer particle analysis system and compared to commercial DED powder. To be able to compare the material quality and to verify DED process parameters, semi-academic sample geometries are manufactured.

10:15am - 10:30am

Evaluation of steady state via thermography during laser and wire based directed energy deposition

Anton Emil Odermatt, Nikolai Kashaev

Helmholtz-Zentrum Geesthacht, Institute of Materials Mechanics, Department of Laser Processing and Structural Assessment

Additive manufacturing of structures in one continuous deposition process is appealing because defects at the start and end-points of a track are avoided. For the evaluation of process stability, a steady state process needs to be reached. A methodology for the determination of the interpass temperature for processes using a positioner for movement of the work piece has been developed. This methodology was applied to a laser and wire based directed energy deposition process. The approach of the steady state process can be described by an exponential growth law. From the interpass temperature a cooling rate can be calculated. The evolution of the interpass temperature can be used for process control and the cooling rate can be related to material properties. A comparison with results from the literature shows that the convergence rate is mainly dependent on the power level of the energy source and the size of the structure.

10:30am - 10:45am

Influence analysis of the layer orientation on mechanical and metallurgic characteristics of DED manufactured parts

Florian M. Dambietz1, Tobias S. Hartwich1, Julian Scholl-Corrêa2, Dieter Krause1, Peter Hoffmann2

1Hamburg University of Technology, PKT; 2ERLAS Erlanger Lasertechnik GmbH

With an increasing trend in product individualization, manufacturing custom-designed solutions and focusing on the explicit industry’s needs are crucial to the manufacturer’s success. Especially within high-tech industries such as aerospace industry, high-strength, large-sized but still lightweight metal parts are required. Although the Direct-Energy-Deposition (DED)-technology offers a proven outset point for targeting this issue, there are few material-, metallurgic-, process-, and geometry specific data available to support the initial design process of such parts. This contribution presents a profound study of different steel- and aluminium materials with respect to their metallurgic and mechanical characteristics. Using a state-of-the art DED-Laser system, tensile test specimens have been manufactured with alternative layer orientations. These specimens are analysed with regard to the required milling oversize, heat-induced stress deformation, metallurgic characteristics and their tensile characteristics. As a result of this investigation, a suitable baseline for the future generation of a DED design-by-feature catalogue is given.

10:45am - 11:00am

Investigation on laser cladding of rail steel without preheating

Christian Brunner-Schwer1, Max Biegler1, Michael Rethmeier3,1,2

1Fraunhofer Institute for Production Systems and Design Techology, Pascalstraße 8-9, 10587, Berlin, Germany; 2Bundesanstalt für Materialforschung und –prüfung, Unter den Eichen, 87 12205, Berlin, Germany; 3Institute of Machine Tools and Factory Management, Technische Universität Berlin, Pascalstraße 8-9, 10587, Berlin, Germany

The contact between train wheels and rail tracks is known to induce material degradation in the form of wear, and rolling contact fatigue in the railhead. Rails with a pearlitic microstructure have proven to provide the best wear resistance under severe wheel-rail interaction in heavyhaul application. High speed laser cladding, a state-of-the-art surface engineering technique, is a promising solution to repair damaged railheads. However, without appropriate preheating or processing strategies, these steel grades lead to martensite formation and cracking during deposition welding.

In this study, laser cladding of low-alloy steel at very high speeds were investigated, without preheating the railheads. Process speeds of up to 27 m/min and Laser power of 2 kW are used. The clad, heat affected zone and base material are examined for cracks and martensite formation by hardness tests and metallographic inspections. A methodology for process optimization is presented and the specimens are characterized for suitability.

11:15am - 12:30pmAdditive Manufacturing: Powderbed, Copper
Location: Room 2
Session Chair: Dr. Stefan Kaierle, Laser Zentrum Hannover e.V., Germany
Room 2 
11:15am - 11:30am

Development of SLM 3D printing system using galvano scanner for pure copper additive manufacturing by 200W blue diode laser

Keisuke Takenaka1, Yuji Sato1, Koji Tojo2, Masahiro Tsukamoto1

1Joining and Welding Research Institute, Osaka University, Japan; 2Shimadzu Corporation, Japan

Selective laser melting (SLM) is one of laser additive manufacturing technologies. Because absorptance of blue light on pure copper materials is higher than that of conventional near-infrared light, a blue diode laser is expected to effective in shaping pure copper parts. In our previous study, we developed a high power and high intensity blue diode laser with the wavelength of 450 nm. Output power and fiber core diameter was 200 W and 100 µm, respectively. In this study, we have developed a SLM machine using galvano laser scanner with the 200 W blue diode laser. The laser power and the scanning speed were changed to form a pure copper parts in the SLM method, and the influence of them on the cross-sectional area of the parts was investigated.

11:30am - 11:45am

3D printing of high-density copper parts using common NIR CW laser systems at moderate powers

Hagen Kohl1, Lisa Schade1, Gabor Matthäus1, Tobias Ullsperger1, Burak Yürekli1, Brian Seyfarth1,2, Bernd Braun3, Stefan Nolte1,2

1Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Germany; 2Fraunhofer Institute for Applied Optics and Precision Engineering IOF, Center of Excellence in Photonics, Germany; 3Nuremberg Institute of Technology Georg Simon Ohm, Germany

Additive manufacturing (AM) of pure copper using laser assisted powder bed fusion (LPBF) at a wavelength of 1070 nm is demonstrated. In comparison to established LPBF materials, pure copper exhibits an extremely high reflectivity for wavelengths around 1 µm and the highest thermal conductivity among other AM materials. Although, pure copper is one of the most interesting materials for AM, the interplay of these characteristics still prevents copper to be applied using common laser-based AM machines. In this work, we demonstrate a wide processing window for 3D-printing of high-density copper parts based on a fiber laser as widely used in common AM machines. These achievements were obtained with the help of a self-developed numerical model that guided our experimental studies during the LPBF process. After process optimization, relative densities over 99 % can be demonstrated without the help of intense preheating or post processing like hot isostatic pressing.

11:45am - 12:00pm

Energy coupling in laser powder bed fusion of copper using different laser wavelengths

Klaus Behler2, Daniel Heussen1, Marvin Kupper1, Nobert Pirch1, Tim Lantzsch1, Johannes Henrich Schleifenbaum3

1Fraunhofer-Institut für Lasertechnik ILT, Aachen, Germany; 2Technische Hochschule Mittelhessen, Friedberg, Germany; 3RWTH Aachen University Lehrstuhl für Digital Additive Production DAP

Highly conductive pure copper is crucial for high current applications in electrical and mechanical engineering. The additive manufacturing of components from pure copper using laser powder bed fusion (LPBF) with conventional machine technology and "infrared" laser radiation (λ ≈ 1070 nm) is challenging due to the high reflectivity of copper for infrared laser light. Fraunhofer ILT has been investigating possibilities to use lasers within the visible spectral range (green @ λ=515 nm and blue @ λ=450 nm) in the LPBF process. It has been shown that there is a potential to improve energy coupling and process stability applying such lasers in the LPBF process. In this paper calorimetric absorptivity measurements are presented, showing the influence of wavelength and process parameters as well as material conditions on the effective energy input for the melting of copper substrate material as well as of powder material.

12:00pm - 12:15pm

Laser powder bed fusion (L-PBF) of pure copper using a 1000 W green laser TruDisk

Guillaume Nordet1,2, Cyril Gorny1, Pierre Lapouge1, Albin Effernelli2, Etienne Blanchet2, Frederic Coste1, Patrice Peyre1

1PIMM Laboratory - ENSAM Paris; 2AddUp

Additive manufacturing of pure copper with lasers is complex using usual near IR laser wavelength, due to a high reflectance (~95 % at 1.07µm) combined with a high conductivity. This results in limited parts density, never exceeding 99%, whereas other metals can easily reach 99.9 % density. A possible way of improvement is to reduce the laser wavelength (from near IR to green) to enhance laser absorption and reduce the power needed to provide deep and stable tracks. In the current work, a detailed study was carried out with the use of a 1 kW cw green laser implemented on a L-PBF prototype. Two objectives were considered: (1) investigating the laser absorbance during single L-PBF tracks at various energy densities and welding regimes (conduction, keyhole) and (2) building various 3D parts and optimizing their density. Finally, parametric study allowed obtaining up to 99.9 % dense parts from pure copper powder.

12:15pm - 12:30pm

Additive manufacturing of conductive copper traces on 3D geometries by laser-sintering

Ejvind Olsen, Ludger Overmeyer

Leibniz Universität Hannover, Germany

These days, additive manufacturing processes cover an extensive range of materials. A new trend is a growing interest in the implementation of additional functions like electrical circuits. Combining full-surface primer and copper ink coating from printed electronics with laser processing enables integrating conductive traces directly on the surface of 3D-printed components. Priming reduces the roughness of the 3D printed (multi-jet modeling) circuit carrier below 100 nm. Afterward, the metal-containing ink is dip-coated, dried, and sintered locally by laser processing. The used laser system includes a focused and pulsed 1064 nm laser beam controlled by a scanner with three optical axes (x, y and z-direction). This research presents a detailed investigation on the influence of 3D geometrical factors like radii and sidewall angle on the resulting conductive trace resistance. Electron beam imaging technology with energy dispersive x-ray spectroscopy characterizes the conductive tracks regarding geometric and material properties.

1:30pm - 2:30pmAdditive Manufacturing: LIFT
Location: Room 2
Session Chair: Antoni Artinov, BAM Federal Institute for Materials Research and Testing, Germany
Room 2 
1:30pm - 1:45pm

Cavitation phenomena in BA-LIFT

Juan José Moreno Labella1,2, Miguel Morales Furió1,2, David Muñoz Martín1,3, Carlos Molpeceres Álvarez1,2

1Centro Láser, Universidad Politécnica de Madrid, Spain; 2Escuela Técnica Superior de Ingenieros Industriales, Universidad Politécnica de Madrid, Spain; 3Escuela Técnica Superior de Ingeniería y Diseño Industrial, Universidad Politécnica de Madrid, Spain

Blister-Actuated Laser-Induced Forward Transfer (BA-LIFT) allows transferring high-resolution voxels or droplets of fluids with a wide range of viscosities. When compared to similar techniques, BA-LIFT stands out in its flexibility in design and the absence of a nozzle that may get clogged. The physics involved in the process is not easy to understand, so image acquisition systems and simulation are the main methods to gain insight into the dynamics of the process. The simulation of the transference process using a Phase-Field Finite-Element Model aids the task of understanding how the transferred material behaves. BA-LIFT long-time secondary effects, such as bulgy shapes and secondary jets, have been simulated including the effects that a mechanically-induced cavitation bubble would induce. An evaluation of its appearance causes has been carried out. Finally, the bubble has been photographed by modifying the setup to avoid optical distortion.

1:45pm - 2:00pm

Laser technologies for the production of microLEDs

Markus Müller, Uwe Wagner, Mandy Gebhardt

3D-Micromac AG, Germany

MicroLEDs have a tremendous potential for future displays. However, there are several technical challenges to overcome prior to widespread deployment of MicroLEDs. One key hurdle is developing a process to release the dies from the sapphire growth wafer. Another is a process to transfer these to the display substrate with micron level precision and reliability.
Laser processing offers several opportunities for MicroLED display production, such as Laser Lift-Off (LLO) to separate the finished MicroLEDs from the sapphire growth wafer and Laser Induced Forward Transfer (LIFT) to move the devices from a donor to the substrate.
In this presentation, laser-based system solutions for the different manufacturing steps for MicroLEDs, will be presented. Integrated process control and monitoring is used to assure stable and reliable operation to ensure high throughput and low yield losses.

2:00pm - 2:30pm

Invited Talk: Additive Manufacturing of Electronics by LIFT

Alberto Piqué

U.S. Naval Research Laboratory, United States of America

Laser-induced forward transfer (LIFT) techniques have generated significant interest for applications in Additive Manufacturing of Electronics (AME). LIFT enables printing of functional materials ranging from silver nano-inks to working devices such as bare-die semiconductor components over a wide range of surfaces in an additive fashion achieving high transfer throughputs. This technique is a non-mechanical, non-contact direct-write process capable of operating in additive and subtractive modes ideally suited for applications in 3D microscale fabrication and in printed electronics. LIFT techniques are well suited for IoT applications as exemplified by their use in prototyping of hybrid electronics and embedded components. This presentation will provide an overview of the current state-of-the-art through examples of structures and circuits made by LIFT and discuss their role in the development of next generation laser-based techniques for AME.

This work was funded by the Office of Naval Research (ONR) through the Naval Research Laboratory Basic Research Program.

2:45pm - 4:00pmAdditive Manufacturing: Directed Energy Deposition 4
Location: Room 2
Session Chair: Dr. Elena Lopez, AGENT-3D e.V., Germany
Room 2 
2:45pm - 3:00pm

Optical monitoring sensor system for laser-based directed energy deposition

Bohdan Vykhtar, Alexander Marek Richter

Fraunhofer Research Institution for Additive Manufacturing Technologies IAPT

To achieve homogeneous material properties and thus high-quality components, a constant melt pool geometry and temperature are essential during the laser-based directed energy deposition processes. Especially at high deposition rates, process instabilities can appear, which lead to deviations in melt pool properties consequently resulting in the discrepancy in the target/actual comparison and, in the worst case, in the disposal of the component. To monitor the continuity of the melt pool properties, this paper presents an optical monitoring sensor system, which is capable of monitoring the process by guiding, filtering, and analyzing the optical signals of the melt pool. The presented sensor system is mounted on-axis to accomplish image acquisition and monitor the melt pool emissions but is also off-axis integrable in hybrid and wire-arc-based (AM)-processes. The system is demonstrated for melt pool monitoring while processing stainless steel and an outlook is given on using that information to control the whole process.

3:00pm - 3:15pm

A measuring system based on chromatic confocal displacement sensor integrated with laser head for monitoring of laser metal deposition process

Piotr Koruba, Adrian Zakrzewski, Piotr Jurewicz, Michał Ćwikła, Jacek Reiner

Wroclaw University of Science and Technology, Poland

The measurement of geometrical properties of a sample during laser material processing is still an open research issue. Thus, the knowledge about the laser focus in relation to sample before, during and after the process is considered as one of the most crucial parameters. In this study, we indicate that the chromatic confocal displacement sensor integrated with laser head can serve as an alternative for current solutions used in monitoring of laser metal deposition process. Therefore, the design procedures of measuring system is described, consisting in numerical modelling, selection of system components. Moreover, in order to determine the functionality parameters of the system it was experimentally characterized in two regimes i.e. off-line and on-line (with and without presence of laser beam, respectively). Additionally, the various methods for spectral data processing were presented. Finally, the preliminary measurement results obtained with the measuring system during laser metal deposition were presented and discussed.

3:15pm - 3:30pm

Rotary straightening of fine wire for LMD-W applications

Sirko Pamin, Maximilian Grafe, Marius Lammers, Jörg Hermsdorf, Stefan Kaierle, Ludger Overmeyer

Laser Zentrum Hannover e.V., Germany

In wire-based high-precision laser applications as micro welding or micro laser metal deposition the straightness of the wire used plays an essential role. Small process windows require constant input conditions and thus straight wire without deformations. Uncoiled commercial wire exhibits a spatial, often helix-like curvature as a result of previous recoil processes on comparatively small reels. With the rotary straightener developed in this work, stainless steel wires with diameters of 75 µm and 100 µm, respectively, were straightened from average curvature levels of 22.56 1/m down to 0.61 1/m by alternating bending. This cold forming process causes crystallographic irregularities (dislocations) and residual stresses, which additionally lead to a rise in hardness and yield strength of the wire. For subsequent laser processes the changed material properties are advantageous, as they increase process robustness and enable a longer wire stick-out.

3:30pm - 3:45pm

Height variation in scanned hot-wire laser surfacing processes

Alexander Barroi, Kai Biester, Laura Budde, Marius Lammers, Jörg Hermsdorf, Ludger Overmeyer

Laser Zentrum Hannover e.V., Germany

The use of hot wire in laser cladding can raise the energy efficiency and the deposition rate of the process drastically. This study shows that when using hot wire, the process faces stronger restrictions to one of the process parameters, the wire nozzle height. A change of three millimeters in wire nozzle height can double the dilution. This is because of the impact of stick out length on the wire heating. But not only the heating has an effect when changing the height, it also changes the wire positioning, a parameter which is sensible for the process stability.

3:45pm - 4:00pm

Automatic changing of weld deposit for additive manufacturing of hybrid metal-glass components using direct laser deposition

Marius Lammers1,2, Kai Biester1, Nick Schwarz1,2, Jörg Hermsdorf1, Stefan Kaierle1, Henning Ahlers2

1Laser Zentrum Hannover e.V., Germany; 2Hochschule Hannover – University of Applied Sciences and Arts, Germany

Direct Laser Deposition is a manufacturing process, which enables Additive Manufacturing of nearly any fusible material. For example metal or glass materials can be processed.

For generating hybrid components out of metal and fused silica, systems technology with coaxial beam guidance using different laser beam sources can be used enabling direct manufacturing of optical, structural and thermal elements. To suit both processes, a wide velocity range regarding the weld material feed from 0.1 to 5 m/min is required.

In this paper a prototype machine for material feeding and changing is presented. The system is designed for metal wire and glass fibre feeding. In order to determine process-critical parameters, preliminary tests are carried out to determine the requirements for the system. The paper also shows how the prototype system performs in terms of changing and conveying the wires as well as fibers with a focus on wear and changing cycles.


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