Austrian conference highlights innovations in metal Additive Manufacturing

March 8, 2017

Austrian conference highlights innovations in metal Additive Manufacturing

Fig. 1 Additive Manufacturing, automotive examples (Source: N.Skrynecki, Kundenorientierte Optimierung des generativen Strahlschmelzprozesses, 2010)

The Metal Additive Manufacturing Conference, MAMC2016, took place November 24-25, 2016, at voestalpine Stahlwelt in Linz, Austria. The two day event was the second in the series organised by the Austrian Society for Metallurgy and Metals (ASMET) and attracted over 220 participants from some 16 countries. The following review, written by Prof Dr Bruno Buchmayr, Montanuniversität Leoben and Prof Dr Jürgen Stampfl, TU Vienna, reports on the event and highlights some of the key presentations.

The technical programme consisted of 35 oral presentations and identified the latest trends and innovative developments along the entire Additive Manufacturing process chain, as well as numerous novel applications. The opportunities connected with such a dynamic technology raises interest in the materials and equipment industries, and indication of the relevance of AM for Austrian industry was given in the opening presentation by Franz Rotter, Head of voestalpine’s Special Steel Division and President of ASMET. Rotter discussed his clear focus on metal Additive Manufacturing, not only with the installation of an AM centre in Düsseldorf in April 2016, but also by offering new AM metal powders to the market.

 

Overview of AM processing

Prof R Poprawe, head of the Chair for Laser Technology at RWTH Aachen, presented a keynote paper that gave an overview of the role of Additive Manufacturing technologies within the envelope of Technology 4.0. Poprawe illustrated the RWTH view on Integrative Production Technology and explained the basics of laser technology at its interaction with the different materials. He presented some examples on graded materials, for example with a ductile core and wear resistant surface, as well as hybrid materials, such as Stellite on copper alloy.

Also discussed were hybrid machine concepts, such as the DMG Mori Lasertec concept, and high speed LMD, using primary energy deposition into the powder, for large components. The move from prototyping to first series production of a large scale motor block was highlighted, along with other interesting new applications. Typical AM examples in the automotive industry were shown (Fig. 1).

Bionic inspired designs, such as lightweight structures, demonstrated to the audience the significantly enhanced design freedom that Additive Manufacturing can offer compared to traditional manufacturing technologies. Ideally, such designs could result from a process where the functionality of the component is specified and the production system designs the product, chooses the material and manufactures the component.

The author stated that integrative research needs knowledge on material, processes, machines, product design and business models. The functionality needs to be translated into a design, addressing the geometry and the material properties. Increasing productivity via multiple laser sources, higher laser power, application of a skin-core principle and new exposure concepts, can all help to reach this goal.

 

Market situation

Benedikt Blitz from SMR Premium provided an interesting overview of the market situation for metal powders. Blitz said that despite impressive growth numbers for AM, and metal AM in particular, the total numbers are still small compared to other metal powder technologies such as press and sinter Powder Metallurgy, HIP and MIM. The analysis showed that although the AM powder market achieved sales of $90 million in 2015, this only represented about 1% (in weight) of the overall worldwide powder market. Interestingly however, it was shown that AM growth is much faster when compared to HIP and MIM, especially in the last two years. Blitz also showed the price range of different metal powders and concluded that the powder price could be around 50% lower in the next ten years.

 

Ni and Fe based alloys processed by Additive Manufacturing

In a further keynote presentation, Prof Dr Thomas Niendorf from Kassel University presented detailed investigations using TEM, EBSD and IPE processes. For steel grade AISI-316L he explained the quantitative difference on service properties, such as fatigue limit, based on the processing conditions; for example, the fatigue limit increased in the sequence: as-built/SLM surface, as-built/turned surface, 650°C/turned surface and HIPed/turned surface. Using X-Ray diffraction, residual stresses were measured in all three directions, with the highest internal stresses found for y-direction (the building direction).

As-built and heat treated samples showed elongated grains in the building direction with a strong texture. This microstructure changed significantly after a HIP-treatment, which led to almost equiaxed, coarse grains without any texture. Prof Niendorf also showed interesting creep curve results for SLM-nickel-base-alloy IN718 with superior creep strength.

 

Process Simulation

Jonas Zielinski, ILT/RWTH, and colleagues investigated numerically the spatial distribution of individual particles and used two different methods, a) a discrete element method and b) a volume-to-fluid method (melting of the powder particles and solidification to a solid). The results provided insights on how the powder bed packing density affects the AM process and the final product quality. The melted area along a single track is shown in Fig. 2.

Austrian conference highlights innovations in metal Additive Manufacturing

Fig. 2 (a) melted volume along a single track; (b) top view of the same track

 

Topology optimisation and lattice structures

The basics and the strength of different approaches to topology optimisation were comprehensively explained by Alexander Walzl of Montanuniversität Leoben. Walzl explained that the different optimisation methods need specific parameters to be successful. The final optimised, complex geometries are however not always producible in a conventional way and that is why AM has a superior position.

Additional case studies with high commercial potential were shown by David Schäfer, FIT Production GmbH. Schäfer also mentioned the balance between cost and benefits especially when they are compared with conventional manufacturing processes. Design aspects are not enough however, there is also a need for support minimisation and reduction of machine cost, which contributes to about 80% to the overall costs. The scrap proportion has to be kept below 30%. Quality assurance measures and data analysis as well as testing (CT scan) are all part of the game, he said.

Karl Neulinger, AIM Sweden AB, highlighted EBM applications and explained the pros of the ELISE concept, a tool for topology optimisation. Similar examples were shown by Stephan Ziegler, ILT/RWTH Aachen, where lattice structures as well as hollow sphere structures were made out of steel. The values for stiffness and specific energy absorption were evaluated for different wall thicknesses and cell sizes to determine scaling laws for practical applications.

 

Conclusion

When compared to the MAMC conference in 2014 it was clear that there has been significant progress regarding materials, understanding of the AM process and exploitation of new applications. For lightweight applications, such as those in the aerospace and space sector, there can be a clear argument for using metal Additive Manufacturing. Topology optimisation, in combination with lattice structures, offers outstanding solutions for many lightweight constructions.

The final decision between conventional manufacturing processes and AM is, for many, still a matter of economics. However, as recent presentations show, there is a significant increase of effort in all fields to promote AM for many interesting applications.

Details of the presentations can found in the conference proceedings, which can be ordered from ASMET secretariat ([email protected]). The third MAMC conference will be November 20-22, 2018 in Wr. Neustadt, Austria.

 

Authors

Prof. Dr. Bruno Buchmayr is head of Chair for metal forming at Montanuniversitaet Leoben, Austria Tel.: +43-3842-402-5600 Email: [email protected]

Prof. Dr. Jürgen Stampfl is leading an AM-group within the Institute for Materials Science and Technology at TU Vienna, Tel.: +43-1-58801-30862

Email: [email protected]

In the latest issue of Metal AM magazine

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