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By Walkerma at en.wikipedia, from Wikimedia Commons
Titanium Oxide
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Rob Lavinsky, iRocks.com, via Wikimedia Commons
Rutile
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Renishaw AM125
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Prof Iain Todd
Titanium 3D-printed car parts could become standard components in ordinary vehicles thanks to important research conducted by engineers at Sheffield University.
Created by Cambridge University spin-out Metalysis, which is based in Rotherham, the process has cut out a significant amount of the costs involved in using titanium - widely considered as an expensive metal - in automotive and aerospace engineering. TCT Magazine + Personalize spoke to Prof Iain Todd, the Director of Sheffield University's Mercury Centre, which specialises in metal processing and powder-based manufacturing.
"Let me tell you a bit about the group. We're the biggest additive manufacturing group you've never heard of," Todd joked. "We're based in the Materials Science and Engineering department at Sheffield. We've been operating since 2007, which is when we got our first Arcam system. We're more focused around electron beams than lasers and we do a lot of work mainly with industrial partners, so our projects are supported by the European Regional Development Fund."
Transforming titanium into a cheap starting material
Todd's team of a dozen engineers has developed what they believe to be world's first 3D-printed titanium car components by changing the way the metal is processed to then be transformed into automotive parts.
"Normally what happens with titanium powder is you take what they call mill grade titanium, which is something that's been three times melted and turned into a block and then rolled. Then it's turned and you remove the material you don't need and are left with a billet of titanium that is re-melted and turned into a powder.
"Titanium starts off as rutile, which is titanium oxide. So you get all the way from a powder in essence to a solid block, which is then turned back into a powder of pure metal. It's a process that's been around for a very long time.
"What we've been doing is taking the ore material - the titanium oxide - and bunging it into a salt bath that's a mix of calcium salts and other chemicals at a very high temperature and you pass electricity through it and it makes the titanium straight from the ore. You don't have to melt it, it just transforms it," Todd explained.
"What [the researchers] found is a way to ... convert rutile sand into titanium directly. It takes out a lot of the difficult, expensive processes so you're left with something that's very low cost.
"Everybody knows we can melt titanium, we've got quite good at it, but getting to the cheap starting material is a real novel piece of work they've done at Metalysis," Todd remarked.
"It's basically saying that if we can do this and cut out all the expensive process steps, you're then left with the powder you need to consolidate the material and we now know that we've got brilliant ways of consolidating powder or turning powder into solid objects - probably one of the best of which is 3D printing," he stated.
Todd admitted that, unlike many of his peers, he prefers to use the term '3D printing' than 'additive manufacturing' or 'additive layer manufacturing' because, he believes, it is easier for a layperson to grasp the concept. "We can call it additive manufacturing, but the public understand 3D printing," he noted.
He went on to explain that electron beam systems or laser systems then transform the good quality titanium powder into parts. Todd's team did this working alongside Metalysis CEO Dion Vaughan and his specialists. The two groups came up with a processing theme for manufacturing in titanium.
"We've been working with Metalysis for a long time on various projects," Todd said. "They gave us the powder and asked us to turn it into an object. That was a Thursday and we had the object out by the Saturday evening."
The process of using this fine titanium powder for additive manufacturing seemed to be something of a revelation for Todd, who admitted he did not think the process would be so easy.
"It wasn't a difficult material to process, which was a bit of a surprise. I was expecting it to be hideous. I was prepared for spits and sparks and the sort of things you normally get when you first put a new material in the machine, but we put the beam on it and it just processes beautifully. It turned out fantastically.
"It was actually far more of a surprise for [Metalysis] than for us, I think. We just said we'd give it a go," Todd laughed.
"This is classic disruptive technology"
Todd's team worked with a small-scale AM125 from Renishaw - a machine that has now been discontinued - which they modified a little in order for it to operate at a very high temperature.
"It's a small machine we bought specifically to do material development," he said. "We've had it for about 18 months. It's great. We've turned around all sorts of bits and pieces in it. It's solid and it does what it’s supposed to do."
He continued: "The small machines that are appearing for gold and jewellery applications are ideal for material development and I think having one of those tucked away in your lab's a good thing. Also, the metal ones are dropping in price. I mean, I'm not buying one for my home, but for £150,000 it's a good size and EOS, Renishaw, all of those, are making good-sized systems for doing quick turnaround material development."
So what is Todd and his team doing with this new process? "We've made some aerofoil sections and impellers," he said. "We've made general aerospace and automotive parts that can be taken to the companies Metalysis works with. We’re now in discussions as to where we take it, but the low-cost 3D printing aspect is a really attractive proposition."
He reiterated: "The obvious thing to go after is this is classic disruptive technology and it's not triple-melted."
"What I would say it's not aerospace grade yet," Todd added. "But if you think of everything that goes into desalination filters, heat shields, exhaust systems … stuff that doesn’t require triple-melted titanium, there's a lot of applications out there where if you go and make it out of titanium, it's prohibitively expensive compared to pretty much any other metal apart from maybe copper. But you end up with something that's quite resistant to temperature, has excellent corrosion resistance and you've got a way of turning it into a low-cost material.
"You think of things like desalination systems and membranes for fuel cells and there's all sorts of things we're not thinking of in terms of what we can do with our time, because some of these are consumable items. You put a filter in and it lasts for a bit, you then have to take it out because it starts being eaten away. So this system has opened the market up.
"Also, this system of manufacturing with titanium is a way of reducing the mass of an object. If you want to take the same form but reduce its weight by 50 per cent you can do it with titanium," he said.
Advanced manufacturing super group
Todd explained that titanium is also far superior to other metals like aluminium when it comes to putting parts together and for making fastenings because it does not corrode as quickly, which is a huge draw for the aircraft and high-end vehicle sectors.
He said that he and his team are keeping an open mind about where their research will take them and they have a watchful eye on what their colleagues around the university are doing. Prof Neil Hopkinson, who spoke at TCT Show + Personalize 2013, is based in the Mechanical Engineering department, while there are other front-running innovators in 3D printing and its related technologies in the institution's structural engineering, medical and composite systems innovation centres.
"There's quite a few of us knocking around. Altogether we form a super group of advanced manufacturing professionals," Todd joked. "We're a broad church. We're interested in the very big and the very small. How do we make objects that are very large, how do we take additive manufacturing out of these constraining boxes and turn it into a large tool. We're quite open about it."
