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Better additive manufacturing processes discussed at AKL

Tom Eddershaw reports from the recent AKL laser technology conference in Aachen, Germany, on the state of additive manufacturing

Calls to optimise the additive manufacturing (AM) process chain, increased specialisation of machines, materials, and software, and a higher degree of communication between the users, integrators, and developers of the technology have been made at the AKL International Laser Technology Congress. The conference, organised by Fraunhofer ILT, ran from 5 to 9 May in Aachen, Germany.

A number of speakers voiced concerns that a new, disruptive technology was being forced upon an industry that was designed for more conventional, reductive manufacturing processes, and that this partly is what is hindering the integration of AM into large-scale production.

There has been much progress made in the field of additive manufacturing, so much so that the finished parts can now be used as functional pieces. The examples most commonly given are in the aviation industry and motor sports – in 2016, for instance, the LEAP fuel nozzle for jet engines designed by General Electric will go into production, with the aim to build 100,000 by 2020. ‘It [AM] is not only a prototyping solution; it is going into mass production,’ William Carter of General Electric commented at the event.

However, motor sports and, to a certain extent, aviation are fields where cost per piece is generally less of a concern and small batches are common. Partly because of the inefficiencies in the processing stages, mainstream use of AM parts is still low and the technology is more frequently used in the design process for prototyping.

MTU, a German supplier of engine parts for the aerospace industry, has seven machines with six of those devoted to production. Dr Karl-Heinz Dusel, who is responsible for the Rapid Technologies department of MTU, said: ‘We have all of our AM machines in one room, but this is only a small part of the process.’

While the actual production of the part is often faster than alternative methods and the tooling costs are removed, Dusel said that sometimes the measuring, finishing, and testing of the part – which can add substantial time penalties to the build – is overlooked. Also, before the build, the platform must be reconditioned, the powder must be checked, and process approval is required to ensure the part will be manufactured correctly with support structures put in where necessary. He said: ‘It’s a very complex process chain, much more complex than some people thought in the beginning.’

In addition, according to Dusel, integrated inspection should be implemented to monitor the quality of the fused powder, layer by layer. He said: ‘This would provide significant improvements in the time taken [for post-processing inspection] and, especially, cost.’ Dusel added: ‘We want to start substituting [AM processed] parts, based on cost reduction and we see there is a chance to do this but we need to optimise the process chain. There is a lot of potential [for improvement] there.’

Maximillian Meixlsperger from BMW has seen a huge increase in demand for AM parts from within the company. So much so that now around 80 per cent of the parts manufactured for prototyping and functional testing are now outsourced to external AM contractors, while only 20 per cent is carried out in-house.

When considering mass-produced parts, the number of defects per part and the inability to detect and halt production during the build is still concerning both the users and researchers. Dr Mike Shellabear, vice president of metal technology at EOS, commented: ‘Lots of things can, and need, to be improved [with AM]. There are huge opportunities for the development of [AM] materials.’

Meixlsperger outlined some of the issues that were slowing progress. He explained that the physical properties of a part are very inconsistent because, often, the powders used are not consistent as they are fed into the machine. This means the powder can react differently to heat stresses causing defects such as cracking and shrinkage of the part, or the particles may not fully fuse together. This, while often causing the part to fail, also means the mechanical properties of a part cannot be simulated and that each part has to be tested individually.

Other aspects were noted during the event in order to capitalise on the technology. Meixlsperger, among others, asked for larger build envelopes, as well as the machines themselves to be built in larger batches in order to bring the price down and make the entire process more attractive to manufacturers.

With such a young technology, it is inevitable that problems will exist. However, there were plenty of positive statements from the conference. Carter at General Electric said the aviation industry was driving AM at GE. ‘People are scared of powder-based materials performance, but the truth is, we are already using them,’ he commented. And as the technology becomes more mature, it will find its way into many more aspects of manufacturing.

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