Ceramics 3D Printing by Selective Inhibition Sintering

Selective Inhibition Sintering (SIS) has been proven effective in producing polymeric and metallic parts. Due to the low cost and high quality of SIS printing, the impact of SIS printing in the 3D printing industry could be disruptive. The potential of SIS is further extended to ceramics, an important but hard to print material, by the same mechanism of creating an easy-to-break sacrificial mold. Due to the high sintering temperature of ceramics, fluid based inhibitors delivered by inkjet printing tend to not be effective in SIS for ceramics. Accordingly, the new concept of inhibition by dry powder delivery is implemented. Preliminary experiments have shown the feasibility and ease of printing of simple ceramic parts. Additional experiments are underway to increase the possible part complexity and accuracy, and to optimize the sintering process.Mechanical Engineerin

Laser melting manufacturing of large elements of lunar regolith simulant for paving on the Moon

The next steps for the expansion of the human presence in the solar system will be taken on the Moon. However, due to the low lunar gravity, the suspended dust generated when lunar rovers move across the lunar soil is a significant risk for lunar missions as it can affect the systems of the exploration vehicles. One solution to mitigate this problem is the construction of roads and landing pads on the Moon. In addition, to increase the sustainability of future lunar missions, in-situ resource utilization (ISRU) techniques must be developed. In this paper, the use of concentrated light for paving on the Moon by melting the lunar regolith is investigated. As a substitute of the concentrated sunlight, a high-power CO2 laser is used in the experiments. With this set-up, a maximum laser spot diameter of 100 mm can be achieved, which translates in high thicknesses of the consolidated layers. Furthermore, the lunar regolith simulant EAC-1A is used as a substitute of the actual lunar soil. At the end of the study, large samples (approximately 250 × 250 mm) with interlocking capabilities were fabricated by melting the lunar simulant with the laser directly on the powder bed. Large areas of lunar soil can be covered with these samples and serve as roads and landing pads, decreasing the propagation of lunar dust. These manufactured samples were analysed regarding their mineralogical composition, internal structure and mechanical properties

Selective laser melting of glass powders

Glass material is extensively utilized in various industrial fields due to its unique properties such as high melting temperature, transparency, as well as high compression strength; however, conventional glass production processes are not optimum for freeform fabrication applications. As such, fabrication of complex geometries in a time and cost effective manner is not currently realizable. Nevertheless, existing fabrication methods and corresponding constraints may be augmented by Additive Manufacturing (AM) techniques in which free form geometries are fabricated based on Computer Aided Design (CAD) data in a layer-wise manner. With respect to this, this study investigates the feasibility of Selective Laser Melting (SLM) of soda-lime and borosilicate glass powder followed by fabrication of test geometries for industrial applications ranging from micrometer to decimeter in size. Initially, SLM process parameter and scan strategy investigations and optimization for different powder particles sizes of soda-lime glass are carried out. SLM fabricated parts are analyzed regarding their bulk density and surface roughness. Furthermore, systematic SLM process parameter optimization both analytically and experimentally, powder rheology, and analysis of the sintering behavior of the borosilicate glass under various atmospheric conditions with the aim of evaluating the density and surface roughness of the SLM processed parts are among the main objectives of this study. Regarding this, process parameter optimization as well as scan strategy adaptation are carried out using different powder particles. Furthermore, powder rheology is analyzed using Hausner Ratio (HR) and dynamic angle of repose (avalanche angle) measurements. With respect to this, bulk and tapped densities as well as the avalanche angle of powders with different particle sizes, distributions, and shapes are studied and classified regarding their powder flow regimes based on the obtained experimental layer-wise lamination results. Moreover, using Hot Stage Microscopy (HSM) viscosity points of different powder particles sizes and distributions are studied and applied for developing an analytical model which is validated by the systematic process parameter SLM study as well as on site thermal process monitoring. Furthermore, SLM optimum process parameters are applied under different working atmospheres with the aim of studying the surface morphology of the SLM fabricated parts. Finally powder bed’s bulk density is optimized by polydisperse powder mixture preparation while keeping the powders’ lamination quality in the desirable flow regime. Results have shown, although developed optimum scan strategy can be applied for a wide range of powder particle sizes, process parameters need to be optimized for each powder individually. The SLM fabricated parts led to an amorphous structure (within the conducted measurement range of 20 ° ≤ 2θ ≤ 160 ° using CrKα radiation) regardless of the powder particle size. SLM fabricated samples from soda-lime glass powders yield a maximum density of 2.43 g/cm3 and a surface roughness (Ra) of 0.88 µm using a 60 W laser power, 0.067 m/s scan speed, 50 µm hatch spacing and a 150 µm layer thickness. Regarding SLM of borosilicate material, optimum flow lamination quality is achieved by creating angular shape monodisperse powders of 200 µm - 212 µm with a HR of 1.21 and an average avalanche angle of approximately 39 °. However, comparison of the flow dynamics of the rounded edge particles to the angular shape particles concluded that the SLM lamination quality could be further improved by using spherical powders. Using optimum process parameters in which the powder bed reaches the viscosity of the half ball point temperature, parts with a bulk density of 1.86 g/cm³ and a surface roughness (Ra) of 10.75 µm are fabricated. Final part’s bulk density of 2.13 g/cm³ is achieved under synthetic air using the volumetric mixed bidisperse particles of 63 µm - 90 µm and 200 µm - 212 µm powders in a ratio of 42 % and 58 % respectively. The surface roughness (Ra) of the fabricated part is improved from 2 µm to 0.9 µm using the CO2 laser polishing process. For demonstration purposes, complex glass geometries have been manufactured, promoting the possibilities of manufacturing custom, complex components via the SLM process

Additive Manufacturing of Flexible Material for Pneumatic Actuators Application

In this paper, endurance of peristaltic linear pneumatic actuators was studied using different hose geometries. Towards this goal, different hose geometries were additively manufactured using Fused Layer Manufacturing techniques of Thermoplastic Polyurethane Elastomer. Material properties of the elastomer were studied using Differential Scanning Calorimetry and the tensile test. The relations between the sample’s print temperature and build direction on the actuator endurance were investigated. Lastly, the relation between the geometry design of the PLPA actuator and its endurance is also discussed. Based on this methodology, authors present results showing that the use of a customized shaped hose with geometrical reinforcement at sides leads to a considerable rise in the hose endurance, when compared with the conventional circular design

3D printing and its applications

Eine zunehmende Anzahl von Artikeln in Publikumszeitschriften und Journalen rückt die direkte Herstellung von Bauteilen und Figuren immer mehr in das Bewusstsein einer breiten Öffentlichkeit. Leider ergibt sich nur selten ein einigermaßen vollständiges Bild davon, wie und in welchen Lebensbereichen diese Techniken unseren Alltag verändern werden. Das liegt auch daran, dass die meisten Artikel sehr technisch geprägt sind und sich nur punktuell auf Beispiele stützen. Dieser Beitrag geht von den Bedürfnissen der Menschen aus, wie sie z.B. in der Maslow’schen Bedürfnispyramide strukturiert dargestellt sind und unterstreicht dadurch, dass 3D Printing (oder Additive Manufacturing resp. Rapid Prototyping) bereits alle Lebensbereiche erfasst hat und im Begriff ist, viele davon zu revolutionieren.An increasing amount of popular articles focus on making models and sculptures by 3D Printing thus making more and more even private users aware of this technology. Unfortunately they mostly draw an incomplete picture of how our daily life will be influenced by this new technology. Often this is caused by a very technical point of view based on not very representative examples. This article focuses on the peoples needs as they have been structured by the so-called Maslow pyramid. Doing so, it underlines that 3D Printing (called Additive Manufacturing or Rapid Prototyping as well) already touches all aspects of life and is about to revolutionize most of them

3D Drucken und die Anwendungen

Eine zunehmende Anzahl von Artikeln in Publikumszeitschriften und Journalen rückt die direkte Herstellung von Bauteilen und Figuren immer mehr in das Bewusstsein einer breiten Öffentlichkeit. Leider ergibt sich nur selten ein einigermaßen vollständiges Bild davon, wie und in welchen Lebensbereichen diese Techniken unseren Alltag verändern werden. Das liegt auch daran, dass die meisten Artikel sehr technisch geprägt sind und sich nur punktuell auf Beispiele stützen. Dieser Beitrag geht von den Bedürfnissen der Menschen aus, wie sie z.B. in der Maslow’schen Bedürfnispyramide strukturiert dargestellt sind und unterstreicht dadurch, dass 3D Printing (oder Additive Manufacturing resp. Rapid Prototyping) bereits alle Lebensbereiche erfasst hat und im Begriff ist, viele davon zu revolutionieren.An increasing amount of popular articles focus on making models and sculptures by 3D Printing thus making more and more even private users aware of this technology. Unfortunately they mostly draw an incomplete picture of how our daily life will be influenced by this new technology. Often this is caused by a very technical point of view based on not very representative examples. This article focuses on the peoples needs as they have been structured by the so-called Maslow pyramid. Doing so, it underlines that 3D Printing (called Additive Manufacturing or Rapid Prototyping as well) already touches all aspects of life and is about to revolutionize most of them

Prozessoptimierung des SLM-Prozesses mit hoch-reflektiven und thermisch sehr gut leitenden Materialien durch systematische Parameterfindung und begleitende Simulationen am Beispiel von Silber

Additive Manufacturing durch Aufschmelzen von Metallpulvern hat sich auf breiter Front als Herstellverfahren, auch für Endprodukte, etabliert. Besonders für die Variante des Selective Laser Melting (SLM) sind Anwendungen in der Zahntechnik bereits weit verbreitet und der Einsatz in sensitiven Branchen wie der Luftfahrt ist in greifbare Nähe gerückt. Deshalb werden auch vermehrt Anstrengungen unternommen, um bisher nicht verarbeitete Materialien zu qualifizieren. Dies sind vorzugsweise Nicht-Eisen- und Edelmetalle, die sowohl eine sehr hohe Reflektivität als auch eine sehr gute Wärmeleitfähigkeit aufweisen – beides Eigenschaften, die die Beherrschung des Laser-Schmelzprozesses erschweren und nur kleine Prozessfenster zulassen. Die Arbeitsgruppe SLM des Lehr- und Forschungsgebietes Hochleistungsverfahren der Fertigungstechnik hat sich unter der Randbedingung einer kleinen und mit geringer Laserleistung ausgestatteten SLM Maschine der Aufgabe gewidmet und am Beispiel von Silber die Parameterfelder für Einzelspuren und wenig komplexe Geometrien systematisch untersucht. Die Arbeiten wurden von FEM Simulationen begleitet und durch metallographische Untersuchungen verifiziert. Die Ergebnisse bilden die Grundlage zur schnellen Parameterfindung bei komplexen Geometrien und bei Veränderungen der Zusammensetzung, wie sie bei zukünftigen Legierungen zu erwarten sind. Die Ergebnisse werden exemplarisch auf unterschiedliche Geometrien angewandt und entsprechende Bauteile gezeigt.Additive manufacturing by melting of metal powders is a method that has been established even for the manufacturing of final products. In particular, Selective Laser Melting (SLM) is currently applied for prosthetic dentistry. In the near future, this technology will access sensitive industries like aerospace engineering. This leads to the need to process new materials. Therefore, especially non-ferrous metals and noble metals must be determined and qualified. These materials have in common a very high reflectivity and an excellent thermal conductivity. In general, these two properties counteract the control of the melt pool and contribute to very narrow process windows. The “SLM” research team of the Aachen University of Applied Science, AcUAS (FH Aachen) systematically investigated process parameter fields for silver. The work focused on a small SLM desktop machine with comparably low laser power. The results are verified using FEA and metallographic inspections and will support future set-ups for complex geometries. Furthermore, the obtained parameter fields are applied to make different geometric objects and to manufactured parts, which are presented

Recycling PA12 powder from laser powder bed fusion through producing filament for fused deposition modelling

The laser-powder bed fusion (L-PBF) process presents advantages over other polymer additive manufacturing processes in terms of part strength and high production rate possible with the technology. The high cost and limited re-use of nylon powder used in the process however limit the large-scale adoption of the technology in industry. This paper investigated the re-use of PA12 powder that is no longer suitable for the L-PBF process through producing filament for the fused deposition modelling (FDM) process. Results from the study showed that parts with good mechanical strength and reasonable dimensional accuracy can be produced using FDM