www.3ders.org

Jan 19, 2015 | By Alec

3D printing is going to space. That is becoming increasingly evident, as more and more 3D printing initiatives are being started by aerospace developers, all the way from 3D printing components for spacecraft to additive manufacturing actually being used in space.

This week, the European Space Agency (ESA) has announced they are also stepping up its 3D printing activities, but in a way that could also change how we 3D print here on earth. For they have just announced that an engineering team from the Trinity College Dublin in Ireland will head an international initiative to develop cold spray 3D printing for aerospace components. The four-year project was announced this week, and the ESA will provide half a million Euros worth of financial backing.

Prof Rocco Lupoi (centre) examines a product sample of his 3D printer and special spray device made at TCD with assistant professors (left) Shaun McFadden and Anthony Robinson. Photograph: Brenda Fitzsimons

Those of you with a background in engineering might say something along the lines of 'but surely cold spray metal manufacturing already exists?' If so, you'd be right. Cold spray manufacturing was developed by the Russians in the 1980s, and the technique has since been used by major metal manufacturers (including GE) and militaries for a variety of applications, but mostly repair of broken metal objects.

In a nutshell, the technology revolvers around spraying very fine metal powders at objects at very high velocities to build components or repair broken ones. Usually, these components rely on low temperature alloy metals, like copper, aluminium and zinc. It is therefore different from conventional 3D printing in a number of ways, particularly in its temperature. Cold spray essentially functions at room temperature, and bonds material without heat, meaning there is no danger of heat-related distortion or damage to the components.

The speed alone is thus enough to bond materials together. This obviously requires exceptionally high speeds to be achieved; as a matter of fact you'll need supersonic speeds twice the speed of sound: 2,472km per hour. Practically, the metallic particles can be added to gasses like helium, which are then sprayed at those velocities. As Professor Rocco Lupoi, who will lead the project at Trinity explained, 'You accelerate the gases to supersonic velocity and if you inject particles into the gas they will also reach supersonic speed. The particles are moving fast enough to penetrate into the surface and bond in a quick way so you can build up say five millimetres of material in a matter of seconds, 1,000 times faster than other techniques.'

Production speed, therefore, is theoretically amazing, but there are a number other advantages as well. It doesn't, for example rely on toxic materials or cause a lot of pollution. As Professor Lupoi, explained, it also requires less raw material, also making it more environmentally friendly. 'Engineering components usually start with a large piece of metal and this is reduced to the size and shape you need,' says Prof Lupoi. 'Cold spray works like a painting machine, applying layer after layer to build up a shape, but done in a matter of seconds.' This means multiple materials can also be easily combined.

The goal of the Trinity College engineers, the coming four years, is to overcome a number of common problems associated with the technique, to make it more efficient, and to make it suitable for aerospace objects. In other words, to make it a 3D printing technology. For as Professor Lupoi explained, the technology is currently not up to the standards associated with 3D printing and especially aerospace manufacturing.

Common technical problems to overcome include precision, the high cost of the necessary components and the limited number of available metals. As Lupoi, who is assistant professor in mechanical and manufacturing engineering, explained, 'This is the largest ESA research project awarded to Trinity, and we will bring cold spray to the next level. We want to make cold spray cheaper without losing performance.'

That latter objective will be relatively difficult, as one of the main expenses is all the helium that is sprayed at high speeds. Decreasing the speed will also decrease costs, but the speed still needs to be high enough to ensure the materials bond. As Lupoi added, 'If you want very high speeds you need helium because it is a very light gas. But the cost of helium is very dear so while the process is relatively simple to do it can be very expensive as well.'

For now, Prof Lupoi's team will include of assistant and associate professors Dr Shaun McFadden and Dr Anthony Robinson, alongside a number of scientists from the ESA: Prof David Jarvis, Dr Wayne Voice and Mr Andrea Amaldi. 'It is a challenging project but there is a detailed technical plan approved by ESA that will address all of these issues in a four-year period.'

However, if successful, more industries aside the aerospace sector can expect to profit from this project. As Lupoi elaborated, 'some automotive parts in modern engines are difficult to manufacture using conventional methods so companies have to compromise on their designs. They see a benefit from this technique.' It could even, though this will take years to realize, become an alternative for other forms of 3D metal printing. If made more affordable, the technique's environmentally-friendly properties could certainly make it an excellent competitor for SLS 3D printing and others. Could we be looking at the 3D metal printing technology of the next decade?

Posted in 3D Printing Technology

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