THE IMPOSSIBLE BECOMES POSSIBLE

The TTC (Manufacturing Technology Centre) in Karlskoga, Sweden, produces metal components with 3D printing that are otherwise impossible to manufacture.

IN THE ALFRED NOBEL SCIENCE PARK in Karlskoga, Sweden, a new technology is proving itself increasingly important to Saab’s future. This is the research and development of 3D printing (additive manufacturing) and industrial 3D X-ray (computer tomography).

TTC began as collaboration between Örebro University and Saab, Lasertech LSH and Bofors Test Center. TTC is now steadily growing, with more companies and universities becoming involved. It is the only centre in Sweden that combines two highly topical areas of research and technology and that keeps the organisation’s expertise and equipment open and available to both the industrial and academic sectors.

“There is a pent-up demand in Swedish industry to learn more about the 3D printing of metal, but previously there was no possibility of testing the technology without investing in machinery and knowledge building,” says Göran Backlund, who is responsible for business development in the Saab Dynamics business area and one of the driving forces behind the creation of TTC. “In the few cases in which the technology is available in a company, it’s not available to other industries. When we launched this project, it wasn’t stated from the outset that it would involve 3D technology. From Saab’s perspective, it was simply important to take part in research and development cooperation with Örebro University, which could provide a long-term supply of skills.”

Now, two years on, there is growing interest in 3D printing, both in the academic world and within industry. In one year, TTC received about 600 visitors on more than 50 different occasions and is currently running five research projects.

Saab has used TTC to test 3D printing and 3D X-ray in various product areas. Saab Dynamics in Karlskoga 3D-printed the breech block for the Carl Gustaf M4 recoilless rifle from titanium. The breech block was printed in two versions, one using electron beam melting and one using laser melting. Then the firing tests took place.

“Both versions were 3D-X-rayed both before and after the firing tests, and it turned out that they didn’t behave any differently from conventionally produced breech blocks,” explains Backlund. “We could also see that the material in the 3D printed breech blocks was free from pores, which means that the 3D printed material was denser than a casting.”

Another example is a heat exchanger that was 3D-printed at TTC for the Gripen fighter. The material used is titanium, and it is made with double outer walls where the flowing media meet. The heat exchanger will now be tested on a rig on the ground, and if the results are positive, flight tests may be carried out.

“3D printing entails a whole new freedom in design terms – anything you can draw, you can generally also print,” says Karolina Johansson, an AM engineer at Lasertech LSH. “The technology makes it possible to manufacture products and components that couldn’t be manufactured by conventional methods such as casting and turning – or that have been far too complicated to manufacture, at least.”

With 3D printing, production takes place in one piece and makes it possible to create hidden cavities and extremely thin walls. No assembly is required, and the lead times are short. Karolina Johansson points to a stator (static component in an electric motor) in tool steel that was 3D-printed on behalf of Scania.

“Production took 80 hours compared with the five months it takes to produce a mould for this type of product,” she says.

Lasertech LSH has two laser melting machines and access to an electron-beam melting machine that is jointly owned by Saab, Lasertech and Örebro University. For Saab’s part, joint ownership means that the group has the opportunity to use the machine for 500 hours per year; a special steering group has been set up to allocate the time between the different business areas.

Through the window on one of the machines you can watch the powder bed get spread over the surface in the chamber, then melted by the programmed laser beam. The next thin layer of powder is spread, and the procedure is repeated. Printing a metal product can take anything from an hour to several days.

“In one year 3D technology has gone from being interesting to strategically important to Saab,” says Backlund. “Just over 150 different metal parts were printed here during 2015, and Saab accounts for 10 per cent of them.”

HOW 3D PRINTING IN METAL WORKS

There are two methods of 3D printing in metal: a cold method known as Selective Laser Melting (SLM) in which a laser beam fuses metal powder together, and a hot method known as Electron Beam Melting (EBM) in which an electron beam is responsible for the melting. The choice of method depends on the characteristics required in the product or component.

The metal powder is spread out in a thin 30–50 μm (micrometre) layer and then the pre-programmed beam melts the metal so that each layer fuses together with the previous one. For each layer the component is moved downwards slightly so that it is built upwards.

The most common materials used are titanium, stainless steel, aluminium, nickel-based metals and various tool steels.

“Production took 80 hours compared with the five months it takes to produce a mould for this type of product.”

Karolina Johansson, AM Engineer at Lasertech LSH

Lasertech LSH is one of the partner companies in TTC. Owner Torbjörn Holmstedt has invested heavily in equipment for 3D printing in both plastic and metal. “I’m planning for a further two machines,” he says. “I’m convinced that the demand will increase significantly within a few years.” Karolina Johansson is an AM engineer specialising in Lasertech’s 3D machines.

Katarina Gustafsson, project manager at TTC, says the centre has hosted 50 company visits over the past year. Five ongoing research projects are linked to the centre. “In five years’ time our goal is to be a leading player in Sweden in 3D printing and 3D X-ray and an established party from an international perspective,” she says.

Göran Backlund, a business development manager in Saab’s Dynamics business area, was the driving force behind the creation of TTC. “The breech block for the Carl Gustaf recoilless rifle was the first one that Saab had printed in metal,” he says. “This involved test samples that were 3D-X-rayed both before and after firing tests.” These X-rays showed that 3D printed components can handle the same loads as conventional manufacturing.

Rebecka Eriksson, a test engineer at Bofors Test Center, works on industrial 3D X-ray. The X-ray beam creates a three-dimensional image of both the outside and inside of an object. “We can use the technology to carry out troubleshooting and deviation analyses, measure pores and cracks, measure the possible volume in hidden cavities and also make copies by scanning an existing object which is then printed,” she says.

FREER THINKING WITH 3D

During 2015 the Saab business area Electronic Defence Systems in Gothenburg, Sweden, tested the manufacture of parts for a water-cooled airborne radar system at TTC.

“We’ve been working on the development of the cooling plate since 2011,” explains Martin Blennius, a systems manager responsible for mechanics and environment, and a specialist in lightweight design. “We have tested different manufacturing methods such as bonding, laser welding, electron beam welding and friction welding – but were not satisfied. We tested dip brazing and it worked, but we were still not entirely satisfied from a quality and performance perspective. So we approached TTC.”

The cooling plate provides a number of challenges. It needs to be dense, light, highly compact and capable of meeting extremely high requirements in terms of its cooling performance at low flows. By using 3D printing, Saab managed to double the efficiency and gain more than 10 degrees in cooling capacity. The next challenge will be to slim the weight down further from 600 grams to a maximum of 480 grams.

“In the process we’ve had help in challenging our limits, and we’ve noticed that we’re now thinking more freely,” says Blennius. “It feels really satisfying.”

 

These four cooling plates were 3D printed in aluminium.