Design for Wire + Arc Additive Manufacture: design rules and build orientation selection

Wire + Arc Additive Manufacture (WAAM) is an additive manufacturing technology that can produce near net-shape parts layer by layer in an automated manner using welding technology controlled by a robot or CNC machine. WAAM has been shown to produce parts with good structural integrity in a range of materials including titanium, steel and aluminium and has the potential to produce high value structural parts at lower cost with much less waste material and shorter lead times that conventional manufacturing processes. This paper provides an initial set of design rules for WAAM and presents a methodology for build orientation selection for WAAM parts. The paper begins with a comparison between the design requirements and capabilities of WAAM and other additive manufacturing technologies, design guidelines for WAAM are then presented based on experimental work. A methodology to select the most appropriate build orientation for WAAM parts is then presented using a multi attribute decision matrix approach to compare different design alternatives. Two aerospace case study parts are provided to illustrate the methodology

Funktionelle Charakterisierung antioxidativer Enzyme aus Toxoplasma gondii

Im Stamm Apicomplexa, zu dem der obligat intrazelluläre Parasit Toxoplasma gondii gehört, waren bis zum Beginn dieser Doktorarbeit noch keine Peroxisomen beschrieben, ein in fast allen eukaryontischen Zellen vorkommendes Organell. Das Markerprotein von Peroxisomen ist das Enzym Katalase, welches Wasserstoffperoxid (H2O2) detoxifiziert. Nach Vorarbeiten in meiner Diplomarbeit wurden Cosmide zur Verfügung gestellt, die die genomische Sequenz der Katalase enthielten. In dieser Doktorarbeit wurde die Sequenz der T. gondii Katalase ermittelt, bei der es sich um eine typische Katalase handelt. Darüber hinaus befindet sich am C-Terminus ein sogenanntes PTS1-Signal, welches für den Import in Peroxisomen notwendig ist. Es wurden Antikörper hergestellt, um die Katalase innerhalb der Zelle zu lokalisieren und mögliche Peroxisomen zu identifizieren. Die vier Seren detektierten im Westernblot eine distinkte Bande, in der Immunfluoreszenzanalyse (IFA) jedoch unterschiedliche Epitope, die einzige Gemeinsamkeit war eine zytosolische, zellzyklus-abhängige Färbung der Zellen. Eines der Seren detektierte eine apikale Struktur in der IFA, welche ein mögliches Peroxisom darstellte. Durch Doppelimmunfluoreszenzanalyse konnte gezeigt werden, dass es sich um eine noch nicht identifizierte Struktur handelte. In dieser Doktorarbeit durchgeführte Fraktionierungsmethoden, sowie Importstudien mit GFP-PTS1 Fusionsproteinen ließen auf eine zytosolische Lokalisation der Katalase schließen. Durch das Ausschalten des Katalase-Gens konnte gezeigt werden, dass die Katalase in T. gondii tatsächlich zytosolisch ist und zellzyklus-abhängig exprimiert wird. Die Funktionalität der Katalase wurde durch einen Enzym-Assay überprüft und die Empfindlichkeit Katalase-defizienter Toxoplasmen gegenüber H2O2 getestet. Durch die Infektion von Mäusen wurden Hinweise für Unterschiede in der Virulenz von Wildtyp und Katalase-defizienten Toxoplasmen gewonnen. Diese Ergebnisse lassen, zusammen mit der ungewöhnlichen Lokalisation der T. gondii Katalase, auf eine Rolle dieses Enzyms unter oxidativen Stressbedingungen schließen. Peroxisomen konnten bisher nich identifiziert werden. Außerdem wurden die Gene zweier weiterer antioxidativer Enzyme aus T. gondii kloniert und in der Zelle lokalisiert, um ihre potentielle Rolle im Zusammenspiel mit der Katalase zu ermitteln. Es handelt sich um Proteine aus der Familie der Peroxidoxime, die in der Lage sind, diverse Peroxide zu detoxifizieren. Eventuell ist eines davon auch in der Lage, als Phospholipase A2 zu wirken. Ihre funktionelle Charakterisierung sowie die Identifizierung weiterer Komponenten des antioxidativen Systems in T. gondii sollten wertvolle Hinweise über das Zusammenspiel zwischen Wirt und Parasit liefern

Enhanced electrochemiluminescence from a stoichiometric ruthenium(II)-iridium(III) complex soft salt

The authors thank NSERC, CFI, FQRNT, PREA, and The University of Western Ontario for generous financial support to this research.Electrochemiluminescence (ECL) and electrochemistry are reported for a heterometallic soft salt, [Ru(dtbubpy)3][Ir(ppy)2(CN)2]2 ([Ir][Ru][Ir]), consisting of a 2:1 ratio of complementary charged Ru and Ir complexes possessing two different emission colors. The [Ru]2+ and [Ir]− moieties in the [Ir][Ru][Ir] greatly reduce the energy required to produce ECL. Though ECL intensity in the annihilation path was enhanced 18× relative to that of [Ru(bpy)3]2+, ECL in the co-reactant path with tri-n-propylamine was enhanced a further 4×. Spooling spectroscopy gives insight into ECL mechanisms: the unique light emission at 634 nm is due to the [Ru]2+* excited state and no [Ir]−* was generated in either route. Overall, the soft salt system is anticipated to be attractive and suitable for the development of efficient and low-energy-cost ECL detection systems.PostprintPeer reviewe

Effect of Tool-Path on Morphology and Mechanical Properties of Ti-6Al-4V Fabricated by Wire and Arc Additive Manufacturing

Ti-6Al-4V components are widely used in aerospace industry. However, it’s not economic to manufacture them in traditional subtractive methods. Wire and arc additive manufacturing (WAAM) is a promising alternative technology for fabricating it efficiently and economically. Tool-path planning strategy is a very important step in WAAM process. This paper investigated the influence of the lap way between layers and layers in tool-path on the Ti-6Al-4V samples fabricated by WAAM. It has been found that the lap way between layers and layers in tool-path do influence the forming quality and especially mechanical properties of the fabricated samples. Samples have different surface quality (smooth or undulating) and defects inside or on the surface of the components. The highest and smallest ultra tensile strength of the fabricated samples are respectively 907.86 MPa, 684.82 MPa. But it has few effect on the grains of the fabricated samples, and they all have cross-sectional columnar grains

The application of knowledge based engineering to design for Wire+Arc Additive Manufacture (WAAM)

Wire+Arc Additive Manufacture (WAAM) is well suited to Aerospace applications, due to its ability to produce medium to large structural parts with good structural integrity, and lower manufacturing cost/ waste material than conventional manufacturing processes. However, designers of WAAM parts need expert knowledge of WAAM to maximise the benefits, and substantial modelling effort is required to develop the digital models that are needed for design assessment and manufacturing. This paper introduces Knowledge Based Engineering (KBE) as an approach to automate WAAM design assessment and manufacturing planning for aircraft structural parts. A prototype KBE tool for WAAM has been developed that can check adherence to WAAM design guidelines, perform cost estimations and automatically generate the CAD models that are required for design assessment and manufacturing planning. The paper also includes a case study design assessment for an aircraft structural part

Residual stress and texture control in Ti-6Al-4V wire + arc additively manufactured intersections by stress relief and rolling

Additively manufactured intersections have the theoretical risk to contain hydrostatic tensile residual stresses, which eventually cannot be thermally stress relieved. The stresses in Ti-6Al-4V wire + arc additively manufactured (WAAM) intersections are lower compared to single pass walls and stresses in continuous walls are larger compared to discontinuous walls with otherwise identical geometry. Thermal stress relief was found to virtually eliminate them. Inter-pass rolling can yield the desired grain refinement, without having any noteworthy influence on the development of residual stresses. The strain measurement itself by neutron diffraction is facilitated by the refined microstructure, because the otherwise textured microstructure produces anisotropic peak intensity, not allowing Pawley refinement. Without rolling, the {101¯1} and {101¯3} family of hcp planes are the only ones that diffract consistently in the three principal directions

A modular path planning solution for Wire + Arc Additive Manufacturing

Wire + Arc Additive Manufacturing (WAAM) has proven its capability to build medium to large metallic parts thanks to its high-rate deposition and its potentially unlimited build volume. Moreover, the low-cost equipment and the ability to deposit various metals make WAAM a strong candidate to become a standard industrial process. However, like all Additive Manufacturing (AM) technologies, the key to manufacturing suitable parts lies in the generation of an optimised path that guarantees a uniform defect-free deposition. Most AM technologies have been able to use traditional path strategies derived from CNC machining, but the specificities inherent to the arc deposition make the use of those solutions unreliable across a variety of topologies. Nevertheless, studies have shown that superior results can be achieved by using a feature-based design approach, but developing a path strategy for each new geometry would be a very time-consuming task. Therefore, this paper introduces the Modular Path Planning (MPP) solution that aims to incorporate the modularity of feature-based design into the traditional layer-by-layer strategy. By dividing each layer into individual deposition sections, this method allows users to adapt the path planning to the targeted geometry allowing the construction of a wide variety of complex geometries. This paper also proposes a software implementation that limits user interventions and reduces user inputs to basic CAD modelling operations. Moreover, the MPP has been compared to a traditional path planning solution and used to build a complex part for industry

Designing a WAAM based manufacturing system for defence applications

Current developments in “Wire+Arc Additive Manufacturing” (WAAM) have demonstrated the suitability of the technology for rapid, delocalized and flexible manufacturing. Providing a defence platform with the ability of on-board WAAM capability, would give the platform unique advantages such as improved availability of its systems and ability to recover its capability after being subject to shock. This paper aims to investigate WAAM technology and define a WAAM based manufacturing system for In-platform applications