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3D Printing: is this the future?: 3D Printing

Ollie Marriage
5 Jan 2011

Forget carbonfibre - metal is getting a whole lot cleverer. find out more and see video and pics here

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Think about metal for a moment, or more precisely think about how it’s constructed and shaped. There are three main methods familiar to all of us: casting (pouring it into a mould), forging (beating it into shape) and machining (carving from a solid block). Well, now you can add a fourth to that list: printing.

Sounds baffling, right, printing a 3D object in metal? But it’s far from science fiction – in fact it’s now being used by a few F1 teams to improve the performance, reduce the weight and cut the lead times of certain parts. Given time it’s likely to find its way into low volume car production, but for the time being it’s the aerospace industry that’s leading the way in what’s known as ALM – Additive Layer Manufacturing.

‘In aerospace, funding research was going more towards composites [carbon fibre etc] and metallics were taking a back seat, but the possibilities with ALM are huge – it’s a game change in manufacturing’, so says Andy Hawkins, lead engineer for ALM at EADS (European Aeronautic Defence and Space company), the firm that builds everything from the Airbus A380 to satellites and helicopters.

So how does it work? Well, the technology has developed hand in hand with CAD, so once something is designed on the computer, it can be sent straight to the printer – just as you would at home with a photograph or document. The printer is obviously the clever bit here.

You start with a fine metal powder – any metal that can be welded, but most often titanium since it’s difficult to machine and costly to process. The powder sits in hoppers and a single layer around 20-30 microns (0.02-0.03mm) thick is spread on a platform by a recoating arm. Using the CAD data a precision laser then ‘draws’ an outline in the powder melting/welding the first layer, before the platform drops 20-30 microns, another layer is spread out and the laser goes to work again. And repeat many times over – the piece with our logo you see here is just 6mm tall, but is made up of 200 layers and took over an hour to construct.

It’s fascinating to watch as the 0.5mm-wide laser dances and zaps over the powder, throwing sparks into the inert argon gas chamber the whole operation is contained in and leaving an impression behind that’s then covered up by the recoating arm. The laser itself penetrates beyond a single layer, bonding the layers to each other. At the end of the process it’s just a matter of removing the welded piece and dusting the excess powder off.

There are limitations: EADS’ largest machine has a chamber that measures a foot square by two feet deep, so that’s the maximum component size – and if you were to build something that size it would take around 50 hours.

The advantages are manifold, as Hawkins points out, ‘there’s no wastage. Often with machining 90 per cent of the material is wasted – for instance on the A380 there’s a strut that’s machined from a 4kg block of titanium and ends up weighing just 100g. Here unused powder is fed back into the hoppers.’

 

Besides that are the precision, strength and weight saving opportunities that ALM offers. An engine cover door hinge on the A380 which used to be cast was redesigned using CAD to analyse the load paths and stresses, then remade using ALM and weighed 65 per cent less.

Hawkins said, ‘the beauty is that complexity doesn’t cost anything. The metal is worked at a molecular level, and the laser can draw any shape you like – structures can be left hollow, we’ve even made chain mail and interlocked rotating wheels just to show what can be done. One of the guys here had his wedding ring made this way, including the engraving on the inside!

‘It’s the next stage of manufacturing, a clean technology with no chimneys pumping out black smoke, that’s lab based and runs on its own 24/7. You basically hit play and walk away.’ At the moment component size and cost are the issues restricting ALM to being mostly a prototyping technology, but Hawkins points out that the way pieces are constructed is already changing, ‘instead of a box we could blow powder into a laser beam and build the part upwards, perhaps using a robot arm.’

It’s fascinating stuff (you can view a couple of videos on the website) and has practically limitless potential. ‘Formula 1 is a sweet spot for the technology as they use high value, low volume parts,’ says Hawkins. Rumour has it that since Daimler is a major shareholder in EADS, several parts of the 2011 Mercedes GP car could be built using ALM. Give it a few years and as the cost comes down, things could really open up. A printed Pagani? Surely only a matter of time. 

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