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