Fraunhofer Institute for Laser Technology

Aachen, Germany

Fraunhofer Institute for Laser Technology

Aachen, Germany
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Petring D.,Fraunhofer Institute for Laser Technology
2016 Conference on Lasers and Electro-Optics, CLEO 2016 | Year: 2016

Laser cutting models provide solutions, varying from analytical steady-state equations based on singular physical sub-processes easily to be calculated, to fully numerical time dependent simulations requiring several days for the calculation of a single cut. In order to solve this dilemma CALCut calculates the three-dimensional, steady-state process including all relevant sub-processes by a combination of semi-analytical and semi-numerical algorithms. Systematic parameter screening is enabled. © 2016 OSA.

Bi G.,Singapore Institute of Manufacturing Technology | Gasser A.,Fraunhofer Institute for Laser Technology
Physics Procedia | Year: 2011

In this paper, restoration of nickel-base turbine blade knife-edges with controlled Laser Aided Additive Manufacturing (LAAM) process was investigated. The alloy contains about 9 weight percent Ti/Al composition, which makes it difficult to repair due to the cracking issue. Infrared temperature signal emitted from melt pool was adopted for process control. The deposition with and without process control was compared. The deposition with process control can avoid the hot-cracking which often occurs during deposition of nickel-base super-alloys. The results showed that the process control can also guarantee a better dimensional accuracy. The microstructure of the deposited layers in the cross-section was examined under both microscope and SEM. It displayed directionally solidified fine columnar dendrites which grew following the change of the heat conduction condition. The EDX line scanning verified that chemical composition remained homogeneous distribution in the deposited thin wall. Spot EDX analysis identified that TiC is most likely the main type of carbides formed at the grain boundaries. The results demonstrated that the LAAM process is feasible for the recondition of the gas turbine blade knife-edges. © 2011 Published by Elsevier Ltd.

Bi G.,Singapore Institute of Manufacturing Technology | Sun C.N.,Singapore Institute of Manufacturing Technology | Gasser A.,Fraunhofer Institute for Laser Technology
Journal of Materials Processing Technology | Year: 2013

In this paper, the process monitoring and control in laser aided additive manufacturing (LAAM) were studied. Some key issues which affect the process monitoring and control were revealed and discussed in detail. The results show that the geometry of the parts affects the melt-pool temperature, especially where the heat dissipation is strongly limited. The power density distribution plays an important role for controlled LAAM process. The laser beam can only be defocused to a certain extent to avoid the insufficient power density due to the excessively enlarged beam size. This can cause defects on the clad surface and in the clad layer. Surface oxidation must be avoided during the process control, because surface oxidation can deteriorate the LAAM process, as indicated by the disturbances of the measured melt pool temperature. With the path-dependant process control, the dimensional accuracy of the deposition can be significantly improved. © 2012 Elsevier B.V.

Gu D.D.,Nanjing University of Aeronautics and Astronautics | Gu D.D.,Fraunhofer Institute for Laser Technology | Meiners W.,Fraunhofer Institute for Laser Technology | Wissenbach K.,Fraunhofer Institute for Laser Technology | Poprawe R.,Fraunhofer Institute for Laser Technology
International Materials Reviews | Year: 2012

Unlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM processed components needs to be clarified. The present review initially defines LS/LM/LMD processes and operative consolidation mechanisms for metallic components. Powder materials used for AM, in the categories of pure metal powder, prealloyed powder and multicomponent metals/alloys/MMCs powder, and associated densification mechanisms during AM are addressed. An in depth review is then presented of material and process aspects of AM, including physical aspects of materials for AM and microstructural and mechanical properties of AM processed components. The overall objective is to establish a relationship between material, process, and metallurgical mechanism for laser based AM of metallic components. © 2012 Institute of Materials, Minerals and Mining and ASM International.

Kumstel J.,Fraunhofer Institute for Laser Technology | Kirsch B.,RWTH Aachen
Physics Procedia | Year: 2013

Polishing of metals by remelting with laser radiation is a method for automated polishing of 3D surfaces. A thin surface layer is molten and the surface tension leads to a material flow from the peaks to the valleys. The achievable polishing quality depends on the material and its quality. Results for polishing of titanium- and nickel-based alloys with cw laser radiation are represented in this paper. Starting from a roughness of Ra=1μm a Ra value of 0.16 μm is achieved in 7 s/cm2 for Ti6Al4V and a Ra value of 0.11 μm is achieved in 10 s/cm2 for Inconel718. © 2013 The Authors.

Schneider F.,Fraunhofer Institute for Laser Technology | Wolf N.,Fraunhofer Institute for Laser Technology | Petring D.,Fraunhofer Institute for Laser Technology
Physics Procedia | Year: 2013

Glass fiber and carbon fiber reinforced polymers with thermoplastic matrix enable high volume production with short cycle times. Cutting and trimming operations in these production chains require the use of high average laser power for an efficient cutting speed, but employment of high laser power runs the risk to induce a wide heat affected zone (HAZ). This paper deals with investigations with cw and ns-pulsed CO2-laser radiation in the kilowatt range in single-pass and multiple-pass processes. Using multi-pass processing at high processing speeds of 100 m/min and above a reduced heat affected zone in the range of 100 μm to 200 μm could be achieved by the ns-pulsed radiation. With cw radiation at the same average power of 1 kW however, the HAZ was 300-400 μm. Also employing ns-pulses in the kW-range average power leads to heat accumulation in the material. Small HAZ were obtained with sufficient break times between subsequent passes. © 2013 The Authors.

Thombansen U.,RWTH Aachen | Ungers M.,Fraunhofer Institute for Laser Technology
Physics Procedia | Year: 2014

Process control for laser-material-processing requires access to characteristic features which qualify the operating-point of the process. For laser-based manufacturing-processes, this can either be achieved by detecting the emission of the process or by detecting geometric properties of the process-work piece interaction. Such illumination is usually provided by lasers emitting in the near-infrared. Inherent properties like coherence of these sources and complex optical systems prohibit a wide adoption. The technological advance in sources such as led's has the potential to deploy small light sources directly to the processing heads but bears new problems in light-ray-delivery, emitter-protection against secondary radiation and cooling. From a scientific point of view, the properties of illumination sources are compared with a special focus on the specific requirements of process observation. © 2014 The Authors. Published by Elsevier B.V.

Nusser C.,Fraunhofer Institute for Laser Technology | Wehrmann I.,RWTH Aachen | Willenborg E.,Fraunhofer Institute for Laser Technology
Physics Procedia | Year: 2011

Laser micro polishing with pulsed laser radiation is a process to reduce the micro roughness of surfaces. During polishing the properties of the laser radiation have a great influence on the results. In this publication the influence of the type of intensity distribution (near-Gaussian, top-hat), of its geometry (circular, square), and of the pulse duration (≈100-1400ns) on the roughness of tool steel (1.2343) surfaces is investigated. Additionally, the influence of the pulse duration on the maximal polishable spatial wavelength is examined. © 2011 Published by Elsevier Ltd.

Petring D.,Fraunhofer Institute for Laser Technology | Goneghany V.N.,Fraunhofer Institute for Laser Technology
Physics Procedia | Year: 2011

Copper materials gain in importance e.g. in view of the coming electro-mobility and therefore also related joining methods for well conducting, fatigue-proof, corrosion resistant and sealing connections are sought after. Welding of copper is generally considered to be difficult, particularly due to its high heat conductivity. Regarding welding with lasers the hitherto unknown coupling efficiency and fear of damaged optics, beam guidance and laser source due to back-reflections make potential users insecure. These are good reasons to systematically investigate copper welding capabilities of the latest generation of fiber-coupled lasers at powers up to 10 kW. The influence of beam power, intensity and material properties on welding depth and seam width versus speed is determined theoretically and practically. © 2011 Published by Elsevier Ltd.

Brandl E.,Airbus | Heckenberger U.,Airbus | Holzinger V.,Airbus | Buchbinder D.,Fraunhofer Institute for Laser Technology
Materials and Design | Year: 2012

In order to produce serial parts via additive layer manufacturing, the fatigue performance can be a critical attribute. In this paper, the microstructure, high cycle fatigue (HCF), and fracture behavior of additive manufactured AlSi10Mg samples are investigated. The samples were manufactured by a particular powder-bed process called Selective Laser Melting (SLM) and machined afterwards. 91 samples were manufactured without (30 °C) and with heating (300 °C) of the building platform and in different directions (0°, 45°, 90°). Samples were tested in the peak-hardened (T6) and as-built condition. The Wöhler curves were interpolated by a Weibull distribution. The results were analysed statistically by design of experiments, correlation analysis, and marginal means plots. The investigations show that the post heat treatment has the most considerable effect and the building direction has the least considerable effect on the fatigue resistance. The fatigue resistance of the samples, however, is high in comparison to the standard DIN EN 1706. The combination of 300 °C platform heating and peak-hardening is a valuable approach to increase the fatigue resistance and neutralize the differences in fatigue life for the 0°, 45°, and 90° directions. © 2011 Elsevier Ltd.

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