Additive manufacturing - Powder power

The promise is to print a part straight from CAD, but after a day of presentations from those who are using additive manufacturing, the delivery of this promise is clearly far from straightforward. Organised by the Association of Industrial Laser Users (AILU, www.ailu.co.uk) – partly because many of the additive manufacturing (AM) machines on the market or being researched use a laser to either melt powder or deposit particles – the workshop didn't promise to deliver all the answers on additive manufacturing, but it certainly gave the answers to some of the questions that engineers and job shop owners in the UK have about the technology, all in a single day. One thing is clear and this is that parts made using AM are now going into service and making money for the businesses that have bought AM machinery. There were 13 speakers at the event, held at the Copthorne Hotel next door to Sheffield United's football ground and a stone's throw from Sheffield's Advanced Manufacturing Park. It was surprising, not just for me but for many of the delegates, at just how many parts are now being made with AM. The best example is Materials Solutions (01905 732160) and the company's technical director, Dr Trevor Illston, says his company has delivered over 6,000 AM parts to industry from the company's six EOS M270 machines. It has an M280 on order too. Up until this workshop, it has been hard to get a steer on exactly how AM is being adopted by industry in the UK. Many of the end users of these parts don't want the publicity, a sentiment confirmed when I overheard a conversation between two delegates, who said: "We're all in the same boat; we can't really show anybody the really good stuff we're doing yet." Sure, we've seen plenty of brackets made by AM, and some weird and complex shapes like Mobius loops, but it's Renishaw's mountain bike frame (01785 285000) that has done the best job of demonstrating the real-world usefulness of AM in a product that all of us can relate to. We must also remember that AM is becoming a household name as it captures the imagination of the general public through the phrase '3D Printing'. Rob Scudamore, AM Special Interest Group chair, and Mike Green, from AILU, spoke to me about this the night before the workshop. I pointed out that 3D printing is becoming a normal, everyday concept, showing them a column in the Telegraph that very day where John Timpson of key cutting company Timpsons was asked about 3D printing and whether he would consider using it to make keys. His reply? He said "perhaps" and that it can be done, but it takes longer than a person does to cut one and costs a lot more. Thankfully, the companies at the workshop believe AM can do much more right now. And it was great to hear from three UK companies that are actively using AM machinery – Croft Additive Manufacturing, Materials Solutions and 3T RPD. Before I go on to talk about some of the issues around wider adoption of AM, the presentation which resonated most with me was from Robin Wilson, from the Technology Strategy Board (TSB). His talk, 'Design and dirty secrets – Getting the best from AM', cut to the core issues. He told delegates that the TSB now "sees AM as a national competency", adding: "We've hung our flag on the mast and we will be investing in AM. We've already funded people to do work in this area, because there's a fantastic agenda to what can be designed. I think we're only 10% in to understanding just exactly what it can do." The 'dirty secrets' aspect, incidentally, relates to the unseen processes around AM. We've kind of been tricked about how it works, partly through media hype. While the concept is sold to us as a draw-a-design-then-push-a-button process, there are multiple processes that have been glossed over, or kept secret. He says these things are no longer secrets, but they remain dirty, and he wants businesses to address these areas. Out of the 18 companies that the TSB is funding, 15 of them are addressing the 'dirty secrets' and 13 are working on the design freedoms AM can give. DON'T IGNORE THE SOFT SIDE But as well as understanding the technical side of AM, Mr Wilson is advising companies to look at the softer, design side of things. "What you make with AM has to look right," he enthuses. "Companies need to think about their branding. What you make might be right aesthetically and it has to work, of course, but is what you're producing desirable? There's some magic stuff with AM and it's where we can make new business, but we shouldn't just focus on the hard technical aspects." One person who is focusing on what AM parts look like is Neil Burns from Croft Additive Manufacturing. He broached the design aspect in his presentation 'A view of the industrial exploitation of AM'. Croft bought a ReaLizer SLM 250 machine ((+49 5251 63232) a year ago after seeing the potential to improve the filters it manufactures and is now the first business in the UK to put 'additive manufacturing' in its name. "With AM we can make filters that have the holes aligned with the direction of the flow," he told delegates. He even had samples in his pocket, which he showed me during lunch, including one of his most popular filters that has had the wire mesh replaced with a lattice made by AM that maintains the shape of the holes and the flow rate. He has had a mixed response to these AM-made filters, though, because they look different. "The flexibility of the machine is fantastic," he offers. "But introducing the new designs to customers is where you get the barriers." Mr Burns isn't alone in experiencing issues with what additively-made parts look like. Stephane Abed from Poly-Shape in France says he's faced similar responses. The main area of his work in AM is in making structural parts lighter. His AM machines make lattices and structural beams that have varying thicknesses, according to where finite element analysis says the stresses are. The result is a part that doesn't look uniform; in actual fact, they look like living insects. If you've seen the film Man Of Steel, then you will have seen similar organic-looking structures envisioned by the film's director to show what the Kryptonian's advanced technology makes. "People are afraid to have such organic-looking shapes," Mr Abed told delegates. "But when they see the weight and the cost saving benefits they give, well, that's when they are more prepared to accept them." What kind of weight saving are we talking about? In terms of an antenna support he made for a satellite, the AM part gave a 34% weight saving; and in the case of a part he made for Thales, there was a staggering 250% reduction in weight. Was there a material cost saving too?, asked a member of the audience. "Yes, for the solar panel pivot," replied Mr Abed. "Sometimes the cost of an AM part will be higher, but the cost saving from putting less weight into orbit is much higher." Poly-Shape is certainly confident with the direction of AM, demonstrated by its investment in 10 AM machines. The firm's buying strategy has been to acquire different models from various brands, instead of having a line of machines from the same supplier. Mr Abed explains why: "Each machine gives us a unique offering, which we exploit. Seven of them use plastic powders and three of them use metal powders. We've just placed an order for the largest metal AM machine too. We'll have the new Q20 from Arcam (HK Technologies, 01788 577288). It gives a much better surface finish on parts and has a build chamber that's 350 mm wide by 380 mm high." All the delegates accepted there is a need for post-manufacturing processes to tidy up an AM part. Some of these involve laser polishing, some involve heat treatments and, sometimes, subtractive machining. Some of the poor surface finishes result from the laser overheating or burning the powder, so research is looking at the exact amount of energy needed in a laser burst to just melt the powder and not completely obliterate it. Days after the workshop, the CEO of US company Sigma Labs Inc said the firm had developed a sensor to do exactly this (www.machinery.co.uk/60555). It is the aerospace sector that most wants the better surface finishes and, at the workshop, Rolls-Royce confirmed it has been exploring AM in "certain applications" for the past 10 years. One of the most poignant comments on the day came from Phil Kilburn at 3T RPD (01635 580284). His company started working with AM in plastics in 1999 and in metals in 2007. The business has doubled in size over the past four years. "What's refreshing," he said in his presentation 'DMLS – Is it a done deal?', "is that people are being really open about the fact that there are still issues with AM. The people selling these AM machines have done a really good job of showing how they can solve everyone's problems and make impossible shapes, but some of the part shapes my customers come to me with just can't be manufactured." Mr Kilburn also agrees that managing the powders is "critical". "You spend a lot of money on the powder, so you've got to use it up," he said. "But some of our customers are asking for parts made with virgin powder. That can be £20,000 spent on powder before you even start and sometimes that just writes off the idea of making it by AM." Mr Kilburn says 3T RPD is looking at the maximum number of powder recycles he can achieve before production is affected. He gets round the problem of leftover degraded powder by using that powder for making prototypes. "The problem is we can't afford to play around with powders," he underlines. "Instead, 3T RPD is part of a project called ANVIL, which is looking into how the powders behave. We're three months into the 32-month project and we're six months into IMPULSE, which is focusing on surface finishes." Mr Abed from Poly-Shape also agreed that powder management is key. He has over 18 different powders that customers can choose their part to be made from, adding: "We like to try new powders to see what results we get. A key part of the process is how we recycle and re-use the powder. The thing with us is that we're speaking about making parts, not just doing prototypes, so the quality of our AM parts is very important." TWI (www.twi-global.com) is undertaking much of the work in understanding the interaction between powders and lasers. Sozon Tsopanos from TWI told delegates how he is looking at increasing the flow rate of powders through nozzles for laser melting deposition (LMD machines) or increasing the number of lasers flashing on a powder bed. And David Wimpenny from the Coventry-based MTC said it is looking at this too, announcing it has ordered an Arcam AWWT (the WT standing for wide and tall) and describing it as an AM machine on steroids. "The hopper takes 200 kg of titanium Ti64 powder," he says. "We now have all these pretty toys (machines), but if you don't control the quality of the powder – or the recycled powder – your parts will suffer." Materials Solutions is going so far as to create its own material/powder laboratory at its Worcester premises, "so we know exactly what we're making", says Dr Illston. And Professor Stewart Williams from Cranfield suggests that we still don't fully understand the laser/powder interaction. Instead, Professor Williams' focus is on making large parts using wire and arc additive manufacturing called WAAM. "Powder processes are expense and limited in size," he told delegates. "While some others here today have said they don't want AM to replace casting and forging, that's exactly what we're trying to do with WAAM," he enthuses. POWDER MANUFACTURER SPEAKS The final speaker on the day was a powder manufacturer, LPW Technology (01925 606 520) and Ben Ferrar from the company was in a great position to address the issues raised over the powder/laser interaction thrown up by the delegates. He showed slides of the effort LPW is putting in to understanding how the powders are used, everything from the shape of the grains to how they package them up for transport by road and air. He says powders need the ability to "soak" up any changes in environment conditions without affecting their quality, but there may come a time when powders will need to be carefully stored in controlled conditions. "The aim of all our work is to give users of AM machines a better knowledge of the powders and how to manage them," he says. "We often have many of our customers say to us, 'we've got this AM machine, what's the best powder to use?'. We have already created an online resource called PowderSolve where buyers of powders can see and track their lifecycle." Mr Ferrar adds that LPW is also looking at which properties of a powder should be optimised and announced the firm is performing in-house research into the flow of powders (using rheometry) and the energy needed to perform this (meter and spread powder layers). It's clear that metal and plastic powders are holding 'magic power' over AM's future direction, but the workshop showed that AM is far from being a 'fairytale' technology. As Neil Burns from Croft Additive Manufacturing put it to me: "Most people think AM is a fad and not for them. But we now sell many of our conventional filters as an AM product. Thinking differently opens doors." First published in Machinery, June 2014