25 October 2022 – Bristol, UK-based GKN Aerospace (GKNA) has developed a proprietary laser metal wire deposition (LMD-w) technology that can be applied to the manufacture of large aerospace components. The company is a manufacturer specialising in airframe and engine products for civil and defence customers, with expertise in metals and composites.
The adoption of additive manufacturing is in line with GKNA’s quest for a more sustainable aerospace future, and the company recognises the value of additive manufacturing technology in optimising the weight/cost of engine and structural components, while acknowledging the challenges they currently face in ensuring their manufacturing is repeatable.
Fundamentally, we need to build confidence,” says Tim Hope, GKNA’s Chief Technologist. With additive manufacturing, repeatability, reproducibility creates trust in the process and the belief that when we deliver a part, we need to deliver it on time to achieve a zero-defect cost. What metal additive manufacturing technology does is reduce the technical risk for us and allows us to better serve our customers.”
Several direct metal laser sintering (DMLS) systems sourced from EOS and renishaw are in operation at GKNA’s facility. In addition, Laser Metal Wire Deposition (LMD-w) technology, developed through the AIRLIFT research programme, is now being used in the company’s engine operations. It is understood that the LMD-w technology allows for a maximum print size of 3 metres and is expected to be used for aerospace structural products.
Although GKNA is already printing flight parts using LMD-w equipment, they still need to further validate the technology: according to their own standards, those of their customers and the authorities. Certification of new processes like additive manufacturing remains one of the biggest challenges for GKNA, and while process monitoring and simulation help with this, open systems are also said to be of great help. GKNA can therefore guarantee the quality of its LMD-w process, but it also needs to establish good links with suppliers for introductory technologies such as powder bed melting.
If your customer is from the aerospace sector, then you need to recognise that all parts of the additive manufacturing supply chain, the end service for flying parts, are for the aviation authorities,” notes Hughes, another of GKNA’s principals. The customer describes the information they need and our whole value chain needs to make a judgement based on that information, depending on the various parts of the chain such as heat treatment, powder suppliers, machine suppliers and so on. If you have empty spaces in there that you can’t see, it’s going to be a challenge.”
In other workshops, GKNA has brought in a Designjet machine developed by Stratasys and HP, an Ultimaker S5, a Formlabs Form 2 and a Markforged Mark 2. These machines (including the Designjet) are often called upon to produce jigs, fixtures and design These machines (including the Designjet) are often called upon to produce fixtures, fixings and design aids, but GKNA will never stop at the desktop platform. After the Designjet, GKNA’s next 3D printing system to be introduced is the Arcam A2.
Among the printed parts demonstrated by GKNA were model tanks and other near-net-shape parts made using LMD-w, as well as certified bracket parts made using DMLS technology. Engine parts are the main order of production for its powder bed melting equipment, while its LMD-w technology may be used to manufacture those large component structures that are difficult to process with DMLS technology. With its strong 3D printing capabilities, confidence is growing within GKNA. The company is active in a range of standards working groups, recognising the progress made by bodies such as NASA, ASTM and SAE in developing such standards in recent years, and maintains good relationships with commercial and academic institutions. In following these standards, however, GKNA has to ensure that the manufacturing process for the technology is not only repeatable, but also consider the cost of generating the dynamic characteristics required for aerospace parts.
Hope reckons: “In aerospace, there are only two challenges with additive manufacturing: the productivity challenge and the certification challenge. Whether you can make the right part the same way every day is a huge technical challenge. And then can you make it cost effective compared to other processes? Once you have identified these two key factors, you have the real winning criteria for additive manufacturing. In terms of future possibilities, these things are great, but to make them happen, we have to be able to get it applied to aircraft, and it’s about regulators and end-user confidence in value for money.”
Hughes added: “Additive manufacturing technology is now at the business end of the hype curve. You’ll see a lot of interesting stuff, but we need to realise this in a real way on real applications to unlock interesting things for the future, and these are about can we get real commercial benefits and long-term returns in the short to medium term? We can all see topology optimisation, functional integration, all that good stuff in the additive manufacturing space. But the confidence of customers and certification bodies in this technology is what it needs to face now as a business issue, and that’s where our focus is.”
GKNA intends to maintain its position as a leader in its field, and Hopper believes that the key to achieving this is to ensure that the business is sustainable: “There aren’t many OEMs in the aerospace sector, so everything we do in additive manufacturing is focused on building supplier trust. If you understand our customers’ needs and can deliver to their deadlines, then you will have a sustainable business. Innovation comes from market demand, business and technical feasibility, and all three need to be combined. But you will only succeed if you can do this repeatedly and in a spirit of trust.”
A set of DMLS printed acoustic liners is on display at the end of the GKNA factory foyer, and Hughes explains that he received the dimensional data for the component on Thursday morning, modelled the part in CAD that evening, assembled it with the process team on Friday, and by Monday morning it was on his desk, where it was eventually used for engine testing. This whole process clearly demonstrates how quickly ideas can go from idea to model, all thanks to the power of metal 3D printing.