Investigation of process improvements through laser preheating in extrusion-based additive manufacturing process
Dennis Meisner, Lukas Forstner, Nikitas Kaftiranis, Stefan Hierl

Fused layer modeling (FLM) is widely used and is gaining more acceptance in the industry mainly due to its material variety and low costs. However, the usage is limited by a process-related anisotropy of the produced parts. The strength and ductility of the printed parts are significantly lower in the build-up direction than perpendicular to it. This is caused by insufficient interlayer bonding resulting from a reduced surface temperature in the process zone. To overcome this problem, a diode laser is integrated into the conventional FLM process to increase the surface temperature between the already printed surface and the newly applied substrate directly at the deposition zone. The investigations carried out show a significant improvement in the mesostructure, as well as a clear reduction in the anisotropy of the printed test specimens.

Keywords: fused layer modeling; laser preheating; anisotropy; interlayer bonding; mesostructure

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Laser polishing as a post-processing tool for DED-LB/P
Yunus Kutlu, Marvin Schuleit, Magnus Thiele, Cemal Esen, Andreas Ostendorf

In this study, the use of laser polishing as a post-processing technique for polyamide 12 samples generated by Directed Energy Deposition (DED-LB/P/PA12) is investigated. The effects of laser power and number of runs on surface roughness as well as mechanical properties are analyzed. Our results show that laser polishing can effectively reduce surface roughness and improve the mechanical performance of DED-LB/P/PA12 samples. Young’s modulus and Ultimate tensile strength increase significantly. In addition, anisotropic behavior was observed, where the mechanical properties were found to be dependent on the orientation of the applied tensile force relative to the DED-layer orientation. Overall, this study demonstrates the potential of laser polishing as a viable post-processing technique for improving the surface quality and mechanical performance of DED-LB polymer parts.

Keywords: DED-LB; polymers; laser polishing, post-processing, additive manufacturing

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Towards integrated optical systems with glass-based additive manufacturing by Laser Glass Deposition
Khodor Sleiman, Fabian Kranert, Axel Günther, Katharina Rettschlag, Moritz Hinkelmann, Peter Jäschke, Jörg Neumann, Dietmar Kracht, Wolfgang Kowalsky, Bernhard Roth, Ludger Overmeyer, Stefan Kaierle

Laser Glass Deposition as an additive manufacturing method is a promising alternative to conventional manufacturing processes for individualized optical components. This process uses a CO2 laser as a heat source to melt fused silica filaments for additive manufacturing. By adapting the process strategy, optical components can be produced, such as waveguides or beam shaping lenses. In this paper, on-chip production of additively manufactured optical waveguides and lenses is demonstrated, paving the way for sophisticated glass-based photonic integration. For this purpose, investigations on the manufacturing of the components under variation of laser power, filament feed rate and line spacing are presented. The focus is to preserve the optical properties of waveguides and lenses and at the same time exploit design flexibility in an automated production environment. The printing of the lenses through fusion of several layers must result in a homogeneous topography. The functionality of the printed components is verified by optical and geometric characterization.

Keywords: Glass additive manufacturing; Direct energy deposition; Laser 3D printing; Integrated photonics; Laser etching

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Additive manufacturing of a titanium flap track by coaxial laser Wire Directed Energy Deposition process
Eva Vaamonde, Pilar Rey, Monica Salgueiro, Marcos Diez

Wire Directed Energy Deposition (W-DED) process is becoming a key manufacturing process in aerospace industry, mainly due to higher deposition rate, ability to build larger structures and high efficiency in material compared with other usual AM technologies, as PBF, or powder-based DED processes (p-DED). Manufacturing of medium-/large-sized metal components is still challenging, especially by laser-based W-DED process, due to a complex heat management along with the requirement of specific atmosphere conditions to reach the specified properties on the deposited material. In this paper coaxial laser wire deposition (W-DED-LB) of Ti6Al4V alloy has been studied to manufacture a large component for the aeronautic industry. Process parameters and different manufacturing strategies have been developed and optimized to reduce the distortion of the final component. Selection of the manufacturing strategy for the manufacturing of the final demonstrator was also supported by simulation. Metallurgy and mechanical behaviour of deposited material was also analysed.

Keywords: laser additive manufacturing; coaxial wire; titanium alloy; distortion; mechanical behaviour

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SLA 3D printer, RECILS enables low-cost and low-loss waveguide bandpass filters for electromagnetic waves at 200-400GHz band
Kentaro Soeda, Kazunori Naganuma, Yoshinori Yamaguchi, Kuniaki Konishi, Hiroharu Tamaru, Norikatsu Mio, Hiroshi Ito and Junji Yumoto

We have successfully fabricated hollow waveguides designed for electromagnetic waves at 200-400 GHz band. These waveguides, with a cross-section of 0.86 × 0.43mm2 and a length of 25.4-mm long formed by our SLA (Stereo-Lithography-Type)-3D printer, RECILS which is featured by its ability to produce palm-sized objects with a high resolution of 20-30 μm at high speed (100 cm3/hour). The surfaces of the hollow structures made of UV-cured resin are copper-plated to confine electromagnetic waves. Experimental evidence confirms that our 25.4mm RECILS-produced, copper-plated waveguides exhibit an insertion loss of just 0.5–1.0 dB within the 200–400GHz band, an efficiency that competes with commercially available metal waveguides. Bandpass filter characteristics of the waveguides in which sub-mm-scale coupled resonator structures are formed by RECILS are in good agreement with the simulation results adopting corresponding models of bulk copper-metal bandpass filter waveguides. These results indicate that the combination of RECILS and metal plating could offer efficient solutions for producing multifunctional sub-THz waveguide devices of any shape at low cost and in a short time.

Keywords: Sub-THz; Electromagnetic Wave; Waveguide; Bandpass Filter Waveguide; SLA 3D Printing; Metal Plating

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Manufacturing of a Fresnel axicon on a millimeter scale using two-photon polymerization
Felix Behlau, Jan Marx, Cemal Esen, Andreas Ostendorf

Two-Photon Polymerization (2PP) is an additive manufacturing process capable of manufacturing arbitrary three-dimensional structures with sub-micrometer resolution, making it an ideal technology for the fabrication of custom optical elements. However, the size of the fabricated optical elements is limited by the field of view of the lens system used during manufacturing. To manufacture large optical elements on the millimeter scale, stitching of the laser paths is required. This paper presents a stitching algorithm that incrementally divides each laser path into areas equal to the field of view of the microscope objective used (500 μm x 500 μm) by calculating the intersections of the laser paths with the area boundaries. Thus, user-defined optics can be automatically fabricated area by area, resulting in millimeter scale custom optics. As a proof of concept, a 3.5 mm diameter Fresnel axicon is fabricated using 2PP. This axicon was used for generation of a ring beam, which is analyzed with a beam profiler.

Keywords: two-photon polymerization; additive manufacturing; Fresnel optics; axicon; beam shaping

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The steady state of the residual temperature in additive manufacturing processes
Christian Hagenlocher, Patrick O’Toole, Rudolf Weber, Wei Xuc, Milan Brandt, Mark Easton, Andrey Molotnikov

The periodic energy input during additive manufacturing results in an accumulation of heat. The residual heat in previously added layers or beads increases the local temperature as new hot material is added. This may results in inhomogeneous distortion and inhomogeneous grain structures in subsequent layers or beads. In this work, the local temperature increase is described by an analytical model to compute the convergence of the residual temperature to a steady state for different additive manufacturing processes. The model is validated by means of infrared imaging during direct energy deposition and thermo-couple measurements during laser powder bed fusion. We demonstrate that the presence of a steady state temperature distribution during additive manufacturing is strongly dependent upon the thermal diffusivity of the material. Furthermore, the model indicates that materials with a high thermal diffusivity, for example Aluminium, require high laser power and high velocity to achieve steady state temperature during additive manufacturing.

Keywords: Additive Manufacturing; Direct Energy Deposition; Heat Accumulation; Cladding; Temperature Field

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Laser deposition and sintering for the fabrication of a multicomponent microelectronic device with Barium Titanate as dielectric component
Maria Canillas, David Canteli, C. Muñoz, Miguel Angel Rodriguez, Miguel Morales, Carlos Molpeceres

This work aims the fabrication of a multicomponent device by using laser technology. The process requires, first, shaping step by additive manufacturing and, second, consolidation step by sintering. In this study, the multicomponent device is a microcapacitor which comprises a dielectric component based on Barium Titanate (BTO) sandwiched between the metallic electrodes. The manufacturing is carried out in two main steps, layer-by-layer deposition of the different components by Laser Induced Forward Transfer (LIFT), and the layer-by-layer sintering by Selective Laser Sintering (SLS). Suitable conditions were achieved for the LIFT deposition of the dielectric and metallic phases. In the case of dielectric component, the conditions and parameters were optimized to print in 3D. For the first time, 2 layers of the in column of a ceramic component were deposited by LIFT. For the sintering step, the conditions for the SLS of the metallic component were achieved while the SLS treatments on the dielectric component were compared with conventional methods.

Keywords: Laser-Induced Forward Transfer; Selective Laser Sintering; Microfabrication; Dielectrics; Multicomponent devices.

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Characterization of polymer waveguides in cavities on 3D substrates manufactured using the Mosquito method
Christian Zander, Laura Fütterer, Ejvind Olsen, Gerrit Hohenhoff, Peter Jäschke, Stefan Kaierle, Ludger Overmeyer

The amount of data to be transmitted is increasing in all technical areas, so that optical transmission lines are also becoming more and more interesting on three-dimensional Mechatronic Integrated Devices (3D-MID). An innovative manufacturing approach for optical waveguides is the additive manufacturing using the mosquito method. In this process a liquid polymer, which serves as the cladding material of the waveguide, is applied into a cavity. A micro dispensing needle is then stitched into the liquid cladding. The material for the waveguide core is dispensed into the cladding and the waveguide is realized by a relative movement of the dispensing needle and the substrate. Finally, the entire structure is cured with UV radiation. This method allows it to create waveguides with different core diameters down to single-mode waveguides. The printed waveguides are characterized regarding dimension and optical transmission behavior.

Keywords: optical waveguides, additive manufacturing, mosquito method, dispensing, polymers