Page 37 - ITA Journal 3-2018

for example, be produced with varying wall thicknesses, cavi- ties and honeycomb structures – like the heavy-duty, lightweight metal, automotive structure from the 3iprint project outlined above.
The production of small batches and even of individual compo- nents is economically viable with 3D printing too. Die casting moulds or forming tools are not needed, which can quickly lead to tool cost savings of several tens of thousands of euros. Individual- ised components, prototypes and spare parts that are rarely needed are therefore considered to be the domains of additive manufactur- ing. 3D printing is not, however, the universal “assault weapon” for attacking the bastions of established production engineer- ing. The manufacturing expert Franz-Josef Wöstmann from the Fraunhofer Institute IFAM in Bremen says: “Additive manufac- turing is a supplement not a sub- stitute.”
3D printing reaches its limits at the latest where large product quan- tities can be made economically with conventional manufacturing processes. This is primarily the case in the high-volume segment of the automotive industry. Addi- tive manufacturing with metal is not productive enough for mass production in series at the present time. Dr Stefan Geisler, Innovation Manager at KSM Casting Group in Hildesheim, is certain: “3D print- ing will be increasing for premium vehicles and for a limited number of components, but it will not succeed in replacing foundries.” He is convinced that the quanti- ties needed in the volume market cannot be reached even with the faster layering speeds possi- ble, for example, using additive
manufacturing with wire. Geisler points out: “What is often forgot- ten is that additive manufactur- ing cannot overcome the laws of physics either. In the nal anal- ysis, all that are involved there too are processes: melting and cooling. There are limits to the speed at which this is possible.” In addition to this, the printed articles need to be machined into nished functional components.
Another de nite disadvantage of additive manufacturing with metal is the high energy con- sumption involved. Dr Wolfram Volk, Professor of Metal Forming and Casting at Munich Technical University, calculates that about twice as much energy as in con- ventional casting is required for the laser melting of metal, from powder production to the nished component.
Additive processes are becoming an increasingly common element of existing process chains. How additive manufacturing and machining can be combined to carry out comprehensive, hybrid processing in a single machining centre is demonstrated by, for example, the machine tool man- ufacturers DMG Mori and Hermle. World market leader DMG Mori supplements laser metal deposi- tion by subsequent machining in the form of turning and milling. Its competitor Hermle extends a multiaxis machining centre by a thermal spraying process using its MPA (metal powder applica- tion) technology, in which metal powder is applied in layers to produce a soundly built compo- nent.
The Berlin company Gefertec is looking to increase manufacturing speed in the additive processing of metals. The 5-axis lines pro-
duced by the expert for additive manufacturing technologies weld wire in layers by the electric arc process. The workpieces pro- duced in this way have outlines that are very close to the nal shape, which reduces the time and tooling operations required for subsequent machining.
Foundry: direct and indirect ad- ditive manufacturing processes The foundry industry can bene t from additive processes in several different ways. Direct additive manufacturing processes give foundries the opportunity to include individual parts or parts that are needed in small quantities in their product portfolio too. In the case of indirect processes, on the other hand, they use additive technologies to produce moulds and cores out of sand as well as models out of plastic. Hybrid technologies involving a combi- nation of conventional casting and additive manufacturing pro- cesses have further potential.
In order to take greater advan- tage of the potential that alumin- ium has to produce lightweight structures in automotive man- ufacturing, the aluminium pro- ducer Trimet is working on the development of a hybrid process chain to link die casting and addi- tive manufacturing. The approach adopted in the context of the joint “CastAutoGen” project speci cally involves the incorporation of 3D printed structures in a die cast component.
German industry holds a prom- inent position among the pro- ducers of additive manufacturing systems, as the BDI (Federation of German Industries) concludes in a position paper. The country’s market share is about 70 per cent with powder bed systems. The
Technical Papers
ITAtube Journal No3/October 2018
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