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Revolution in the air, as printing goes to the next dimension

The art of printing in 3D has come of age, as items large and small get a manufacturing makeover.

Once upon a time, it took years – decades even – before a new product entered the market and became mass produced. Now that same process can take place in a matter of weeks or even days.

After years in the backrooms of experimental engineering labs, 3D printing, essentially a huge extension of computer-aided design, is revolutionising the way anything from small household products to large items of industrial equipment are designed and built.

Some pundits, such as technology guru Steve Sammartino, go so far as to predict that, within a matter of years, 3D printing could have an even bigger impact on society than the internet and mobile technologies.

Already, a staggering variety of objects have been printed in 3D: from dainty chocolates and necklaces to ceramics, metal jewellery, dresses, prosthetic jaw bones, guns, smartphone cases and – on a grander scale – even parts for jet engines.

A key goal of additive manufacturing, as the process is now known, is for printers to build objects directly from computer aided design files in hitherto unthinkably short times.

One machine in the US, for instance, can already build objects up to 500 times faster than the conventional production process could manage – and that's only the beginning. US aerospace giant Lockheed Martin, meanwhile, has plans to print objects of up to 30 metres in length for use in a variety of aeronautical applications.
Another American company, Made in Space, is building 3D printers for use in orbit. A printer sent to the International Space Station was used to build a wrench from a template produced on Earth.There are also plans afoot for an even more sophisticated printer that will let ground controllers build useful objects in orbit.

Such devices would come in particularly handy for building miniaturised satellites, known as CubeSats, using components stored on the space station.

How they work
​Most 3D printers are powerful devices, with more processing power than the computers that landed humans on the Moon. In essence, they build three-dimensional objects from 3D computer models by fusing or spraying on various materials, layer by layer, many times over.

Most printers tend to work with plastics such as nylon or ABS, which stands for acrylonitrile, butadiene and styrene, used for providing a chrome-like metallic finish to some plastics. Other materials can also be printed. NASA, for example, has prototype astro-food printers for creating digital recipes, including several for pizzas – especially for long-duration journeys.
Printers of this kind rely on a series of small cartridges.The ingredients are stored in powdered form and then added to the printer's mixing chamber, blended with water and oil and finally heated and sprayed in successive layers on to a base.

This is basically the idea behind a kitchen-ready food printer by US company 3D Systems, which uses a combination of dry powders and water to print sugar, chocolate or candy in a variety of delicate designs.

Going metallic

3D printing is also capable of making metallic components using lasers or an electron beam to melt metal alloy powders, such as titanium, aluminium and nickel alloys.

A common feature of the metal and some plastic 3D printing processes is that the components are built up by fusing very fine metal or plastic powder, says Dr Robert Hobbs, the chief executive of Amaero​ Engineering, a spin-off company of Monash University's Centre of Additive Manufacturing (MCAM).

"Here, at Monash, we use two techniques to print parts in metal using lasers," he explains.

Technique one

​The first, the powder bed process, builds up individual parts, layer by layer. "First, we have a 3D computer model of the part to be printed and, using the computer, we divide this model into a series of very thin horizontal slices," Dr Hobbs says. The engineers then use this assembly of slices to drive their state-of-the art printing machine.

"In our machine, we start with a flat metal base plate and wipe a very thin layer of powder, about 50 microns thick – about the thickness of a human hair – over it. Then we trace a pattern on the powder using an overhead laser and this melts the powder onto the base plate."

After that, the whole bed drops down by 50 microns and then another layer of powder is spread over it. The laser then traces the pattern corresponding to the next slice and melts this layer onto the one below. "We repeat this process many thousands of times until the whole part is built," he notes.

At the end of the build process, the engineers remove any powder that has not been fused by the laser, and sieve and recycle it into the machine for the next part. The part is then removed from the printer and cut off free of the base plate.

Technique two

The second process involves blown powder. Here, the laser head is mounted on a robotic arm that moves around in free space. Powder is blown into the laser plasma, melted and deposited onto the layer beneath, Dr Hobbs explains. "This process can build very large parts, though it's slow and can take several days to build a part.

"After building the part, engineers have the matching surfaces machined, drilled and tapped so that they can be assembled in the way of normal parts. "In some cases, we can combine several parts and build them in one go – thus reducing the complexity of assembly," he says.

Aerospace designs

​Airline manufacturers are already using this process to make prototype parts in order to test out promising new designs. "One of the first applications of the process for large scale manufacture of jet engines will be for fuel injector nozzles," Dr Hobbs notes.

General Electric, in fact, has announced plans to make the fuel injection nozzles for their new LEAP engine, using the powder bed process.

Engineers, meanwhile, have printed and assembled components for the world's first 3D printed jet engine, a product of a Science and Industry Endowment Fund collaboration between Monash

University, CSIRO, Deakin University, Microturbo of the Safran Group and Amaero.
The Monash engineers used their laser-based processes while at Lab 22 in CSIRO, Clayton, Melbourne; the CSIRO engineers employed a high-tech Arcam Electron Beam Melting printer, in combination with cold spray technology.

"This project has shown that test parts can be produced in days instead of the usual months for conventional processes," Dr Hobbs says.
MCAM head Professor Xinhua Wu says the centre is working with manufacturers, such as French aerospace group Safran, which is experimenting with new processes to make components lighter and cheaper. MCAM and Amaero have printed a second engine, now displayed at Microturbo's headquarters in Toulouse, France.

"When industry wants particular performance benefits, under particular conditions, we understand what they need and why, and we are increasingly able to deliver it. I believe the next generation of aerospace manufacturing may well start here, in Australia," Professor Wu says.