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Bach F.-W.,Leibniz University of Hanover | Hassel T.,Leibniz University of Hanover | Biskup C.,Leibniz University of Hanover | Hinte N.,Leibniz University of Hanover | And 2 more authors.
BHR Group - 20th International Conference on Water Jetting | Year: 2010

One of the disadvantages of pure water jet cutting or ablation is the relatively limited erosive capacity resp. cutting depth in harder materials (metals, ceramics, tougher plastics and so forth). The usual way to handle this is to add abrasive sand to the jet, resulting in a highly increased cutting performance. However, abrasives are not always desirable, f. e. when contamination with dusts has to be avoided. In addition, the abrasive particles only reach approximately 60% of the water jet's velocity due to friction and a limited acceleration process. In order to address these issues, the authors have designed a process implementing ice particles as abrasive material. In order to achieve higher velocities using lower pressure levels, the process is based on an in-situ phase shift of the water jet immediately after having left the nozzle, which is obtained by precooling the water at 200 MPa down to -20 °C by means of a high pressure thermal exchanger. The following text describes the current state-of-the-art, the proposed experimental setup, some preliminary performance analyses and prospects of further research. © BHR Group 2010. Source


Rickenbacher L.,ETH Zurich | Spierings A.,Inspire AG fur Mechatronische Produktionssysteme und Fertigungstechnik | Wegener K.,ETH Zurich
Rapid Prototyping Journal | Year: 2013

Purpose - The integration of additive manufacturing (AM) processes into a production environment requires a cost-model that allows the precise estimation of the total cost per part, although the part might be produced in the same build job together with other parts of different sizes, complexities and quantities. Several cost-models have been proposed in the past, but most of them are not able to calculate the costs for each single part in a mixed build job or are not suitable for Selective Laser Melting (SLM). The purpose of this paper is to develop a cost model, including all pre- and postprocessing steps linked to SLM. Design/methodology/approach - Based on collected data and the generic cost model of Alexander et al., an adapted model was developed for the SLM process including all required pre- and post-processes. Each process was analysed and modelled in detail, allowing an evaluation of the influences of the different geometries on the cost of each part. Findings - By simultaneously building up multiple parts, the manufacturing as well as the set-up time and therefore the total cost per part can be significantly reduced. In the presented case study a cost reduction of 41 per cent can be achieved in average. Originality/value - Using different cost allocation algorithms, the developed cost model enables a precise determination of total cost per part avoiding that any geometry is preferred in simultaneous manufacture. This helps to optimize build jobs and to manufacture SLM parts more economically by pooling parts from different projects, whereas the cost per part can still be precisely determined. © Emerald Group Publishing Limited. Source


Spierings A.B.,Inspire AG fur Mechatronische Produktionssysteme und Fertigungstechnik | Starr T.L.,University of Louisville | Wegener K.,Inspire AG fur Mechatronische Produktionssysteme und Fertigungstechnik
Rapid Prototyping Journal | Year: 2013

Purpose - Additive manufacturing technologies such as, for example, selective laser melting (SLM) offer new design possibilities for a wide range of applications and industrial sectors. Whereas many results have been published regarding material options and their static mechanical properties, the knowledge about their dynamic mechanical behaviour is still low. The purpose of this paper is to deal with the measurement of the dynamic mechanical properties of two types of stainless steels. Design/methodology/approach - Specimens for dynamic testing were produced in a vertical orientation using SLM. The specimens were turned to the required end geometry and some of them were polished in order to minimise surface effects. Additionally, some samples were produced in the end geometry ("near net shape") to investigate the effect of the comparably rough surface quality on the lifetime. The samples were tension-tested and the results were compared to similar conventional materials. Findings - The SLM-fabricated stainless steels show tensile and fatigue behaviour comparable to conventionally processed materials. For SS316L the fatigue life is 25 per cent lower than conventional material, but lifetimes at higher stress amplitudes are similar. For 15-5PH the endurance limit is 20 per cent lower than conventional material. Lifetimes at higher stress also are significantly lower for this material although the surface conditions were different for the two tests. The influence of surface quality was investigated for 316L. Polishing produced an improvement in fatigue life but lifetime behaviour at higher stress amplitudes was not significantly different compared to the behaviour of the as-fabricated material. Originality/value - In order to widen the field of applications for additive manufacturing technologies, the knowledge about the materials properties is essential, especially about the dynamic mechanical behaviour. The current study is the only published report of fatigue properties of SLM-fabricated stainless steels. © Copyright - 2013 Emerald Group Publishing Limited. All rights reserved. Source


Spierings A.B.,Inspire AG fur Mechatronische Produktionssysteme und Fertigungstechnik | Herres N.,Campus Buchs | Levy G.,Inspire AG fur Mechatronische Produktionssysteme und Fertigungstechnik
21st Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference, SFF 2010 | Year: 2010

A recent study confirmed that the particle size distribution of a metallic powder material has a major influence on the density of a part produced by SLM. Although it is possible to get high density values with different powder types, the processing parameters have to be adjusted accordingly, affecting the process productivity. However, the particle size distribution does not only affect the density but also the surface quality and the mechanical properties of the parts. Therefore, this study compares three different particle size distributions depending on the laser scan velocity and two layer thicknesses of 30μm and 45μm. By using an optimized powder material a low surface roughness can be obtained. A subsequent blasting process can further improve the surface roughness for all powder materials used in this study although this does not change the ranking of the powders with respect to the resulting surface quality. Source


Spierings A.B.,Inspire AG fur Mechatronische Produktionssysteme und Fertigungstechnik | Herres N.,Inspire AG fur Mechatronische Produktionssysteme und Fertigungstechnik | Levy G.,Inspire AG fur Mechatronische Produktionssysteme und Fertigungstechnik
Rapid Prototyping Journal | Year: 2011

Purpose - A recent study confirmed that the particle size distribution of a metallic powder material has a major influence on the density of a part produced by selective laser melting (SLM). Although it is possible to get high density values with different powder types, the processing parameters have to be adjusted accordingly, affecting the process productivity. However, the particle size distribution does not only affect the density but also the surface quality and the mechanical properties of the parts. The purpose of this paper is to investigate the effect of three different powder granulations on the resulting part density, surface quality and mechanical properties of the materials produced. Design/methodology/approach - The scan surface quality and mechanical properties of three different particle size distributions and two layer thicknesses of 30 and 45mm were compared. The scan velocities for the different powder types have been adjusted in order to guarantee a part density ≥ 99.5 per cent. Findings - By using an optimised powder material, a low surface roughness can be obtained. A subsequent blasting process can further improve the surface roughness for all powder materials used in this study, although this does not change the ranking of the powders with respect to the resulting surface quality. Furthermore, optimised powder granulations lead generally to improved mechanical properties. Practical implications - The results of this study indicate that the particle size distribution influences the quality of AM metallic parts, produced by SLM. Therefore, it is recommended that any standardisation initiative like ASTM F42 should develop guidelines for powder materials for AM processes. Furthermore, during production, the granulation changes due to spatters. Appropriate quality systems have to be developed. Originality/value - The paper clearly shows that the particle size distribution plays an important role regarding density, surface quality and resulting mechanical properties. © Emerald Group Publishing Limited. © Emerald Group Publishing Limited. Source

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