Not fast enough

For those thinking additive manufacturing (AM) is still in its infancy, think again. According to the Wohlers Report 2011, AM is already a $1.8 billion industry which will become $5 billion by 2020. Additive is healthy, and nowhere more so than here in the UK, judging by the quantity and quality of the research and innovation that is taking place. First up at the AILU event was Richard Hague, professor of innovative manufacturing at Loughborough University and head director of its Additive Manufacturing Research Group. Professor Hague's work centres on the use of multi-functional AM, stating that "the future is in the build of multi-material metal components. AM parts that combine mechanical, conductive and optical functionality will exploit greater design freedoms". WEIGHT LOSS IS MAJOR GAIN Like many working in this area, Professor Hague says the big AM gains are in component weight loss, with "compelling" percentages of up to 60% available in some instances. The university has recently worked with Delphi, achieving huge weight reductions for a diesel pump having complex internal channels, but there is a snag. "The speed isn't there yet; I would be disingenuous if I didn't say that," he says. "Metallic systems need to speed up…but they will." One of the factors that might help accelerate AM cycle times is the entrance of Renishaw (01453 524524) into the marketplace. Following its acquisition of MTT last year, Renishaw has grand ambitions, as Stephen Crownshaw, the company's AM sales development manager, explains. "The scope for complex metal parts is vast," he says. "Currently, AM is ideal for small parts such as dental crowns, bridges and tooling. AM components shouldn't be things that can be made on a 5-axis machining centre, because you'll never win on speed. Large parts, particularly, still take too long using AM and it will require a step-change in technology to take on components such as those used in aircraft. "Here, we not only require greater speed, we need better in-process control documentation. Aerospace manufacturers need to know what's going on inside the melt pool and see what's happening layer-by-layer to give complete part validation. We want to hone in on this, but it's a long way off at present." The big news from Renishaw is its acquisition of the former Bosch site at Miskin, near Cardiff. This 460,000 ft2 site will produce all of the company's AM systems (which are based on SLM – selective laser melting technology) from Q4 2012. It is three times the size of the existing MTT facility at Stone in Staffordshire, which is set to become the R&D arm of Renishaw's AM business. "Renishaw wants to take AM to the next level – we want to sell banks of machines for production purposes, not just one-off for prototyping," says Mr Crownshaw. "We aim to be selling in the high hundreds globally in five years' time." The Welding Institute (TWI) is also firmly engaged in research based on SLM, as well as by laser powder deposition. The organisation can point to many recent successful projects, including: seal fin repair for low pressure turbine blades, using a Huffman HC-205 (+1 317 695 8372) CO2 laser with integrated camera recognition system; and the production of a freeform titanium leading edge for composite fan blades – TWI reports that 700 mm long prototypes have been produced using a Trumpf (0844 482 0188) system. The TWI has also had success using a SLM100 machine from Realizer (+49 5251 63232) on medical parts such as custom hip implants and cochlear hearing aids. The latter – manufactured using a titanium grade 2 powder – is now a production process, generating parts at less than €60 each (30,000 parts per year). While 200 W and 400 W SLM systems are available, TWI is currently working with industry partners on the development of a 1 kW SLM system. "Right now, if you increase the power using existing systems, surface finish tends to deteriorate," explains Dr Emma Ashcroft, section manager for laser AM at TWI. "Having a 1 kW machine would increase productivity, not just through greater speed, but via changes to layer thickness and hatch spacing." REMANUFACTURING RESEARCH In similar vein to work undertaken at TWI, Professor David Wimpenny, technology manager, net shape manufacturing at the MTC, also works in cost-effective and efficient remanufacturing research projects using AM. Remanufacturing is the process of returning used parts to as-new condition. According to Professor Wimpenny, this activity contributes £5 billion to the UK economy every year, despite its low profile. However, at present it's a largely manual and skilled process that is both inefficient and expensive, offering poor repeatability. As a result, the MTC is involved in a three-year, £1 million Technology Strategy Board-funded project called RECLAIM – the REmanufacture of high value products, using a Combined LAser cladding, Inspection and Machining system. With an AM cell based on Huffman technology, the MTC says it has already enjoyed success repairing stainless steel turbocharger nozzle rings. The process starts by milling away the damage before scanning the part, using a Renishaw Sprint probe. Based on the results, an NC cladding process then deposits the repair material where required, before the part is blend-machined using adaptive CAM developed by Delcam (0121 683 1000). Aerospace compressor blades have also been successfully re-tipped, while turbocharger turbine wheels (with damaged blades), for Cummins, have also been returned to original equipment specifications. The latter are now with Cummins for performance testing – the MTC reports that it is eagerly awaiting results. The second half of the workshop switched emphasis towards current industry experience. Jonathan Meyer, UK head of the Metallic Technologies Group at EADS Innovation Works, Filton, is exploring the potential for AM in various applications where it can save material waste. Many aircraft programmes have a buy-to-fly ratio of 10 (only 10% of the material ends up on the plane – the remainder is machined away), but current, alternative near-net-shape processes, such as forgings and investment castings, feature long lead-times (up to 95 weeks in some instances) that can present a risk to projects. "For small, complex parts, we see potential for AM," he says. "We've already optimised a nacelle fan cowl door hinge for the A320, saving 60% in weight over cast steel. Furthermore, the first electron beam melting (EBM) part in a load-bearing situation went into space last year – this was produced using an Arcam system (+46 31 710 3200). In the future, we could see savings in mid-sized parts, using AM to produce titanium pre-forms and then machine to a finish, which would present massive cycle time savings. "Of course, large pre-form manufacture is the ultimate end goal, but this is some way off, although the WAALM [wire + arc additive layered manufacture] system at Cranfield University looks promising, with deposition rates of 4 kg/hr across a work envelope of 4 by 2 by 0.3 m," he continues. "I would actually urge AM systems developers to concentrate more on speed than on size. If we can go quicker, the market would see adoption rates an order of magnitude higher." These sentiments are echoed by Jeff Allen, who works in manufacturing technology at the Rolls-Royce aero engine plant at Derby, where M270 SLS machine technology from EOS Electro Optical System (01926 623107) is deployed. And despite the presence of Concept Laser (ES Technology – 01327 701120), Renishaw and others in the market, Mr Allen says all such machines need to be made faste, if they are to be considered a series production technology. "These machines are basically rapid prototyping tools," he says. "As an everyday resource to help keep engine development programmes moving and allow last minute changes, they are great. However, we're now looking at production parts, which are an entirely different proposition." Mr Allen says that with typical build rates of 25 g/hr, it takes 40 hours to make a 1 kg part. At a cost of £100 per hour, such a part comes in at £4,000. "Not even in the right ball park," he underscores. "If the cost was £400, it would be getting there, while £40 would really be competing. The trouble is, we need a speed increase of x100 and people are getting tired of waiting for AM to accelerate. I've been involved in this technology for 10 years and it hasn't really progressed. I'm getting fed up. We also have issues concerning expensive powder and small tank sizes." TELL IT LIKE IT IS Ultimately, Mr Allen describes EBM as "fast and nasty" and SLS (selective laser sintering) as "slow and smooth", adding that "we need the best of both worlds. If I was a betting man, I would back EBM for the future". Stuart Jackson, UK regional manager at EOS is able to confirm strong support for his company's SLS technology. With a target of €64 million for 2010/11, EOS ended up hitting €94 million. The company also delivered its 1,000th system in 2011, although admittedly two-thirds of these systems are polymer-based, not metal. The main new development at EOS is a 400W system (EOSINT M280) giving higher build speed and improved surface finish with aluminium, due to this material's high heat conductivity. The company also has a new module (IPCM-P) capable of handling powder without physical contact. Arguably, the most eye-opening presentation was saved until last. Steve Rommel of the Fraunhofer Institute for Manufacturing, Engineering and Automation in Stuttgart, spoke passionately about the use of EOS FORMIGA P100 technology (polymer-based) to develop bionic designs via the SLS process. Bionics is the study of nature to create technical solutions. Fraunhofer has already teamed up with Festo (0800 626422) to create the award-winning 'elephant trunk' robotic arm (Bionic Handling Assistant) that is both rigid and flexible in 11 degrees of freedom. Weighing less than 2 kg, this robotic arm is designed as an addition to a robot, the idea for which came from the study of crabs, while the gripper itself is based on a fish fin. So what's next? Well, a crawling robot based on the movement of spiders no less (there's already a prototype). Box item Two materials, one part The work of Dr Adam Clare, lecturer of advanced manufacturing at the University of Nottingham, focuses on the use of AM to create functionally graded materials from metal matrix composites – applying expensive materials only in the areas where they are needed on the part. In essence, Dr Clare says his work is like "trying to apply an Objet Connex type process [simultaneous jetting of multiple polymers] to lasers and metals". To help achieve this, Dr Clare and his team have created a hybrid material laser (2 kW fibre) deposition system with 4-axis CNC table and wire/powder feed. Composite materials currently under review for MMC components include: Inconel 625/tungsten carbide; Ti-6Al-4V/tungsten carbide; and Ti-6Al-4V/Ti2B. ImageTrumpf laser deposition system First published in Machinery, June 2012