3D printing of metals has become a ‘hot’ topic in mechanical engineering. A combination of laser and fine metal powder is used to create pieces that cannot be produced with any other production technology.
Space-time methods, developed in the world of Big Science and the aerospace industry, are quickly spreading to the sphere of more conventional machine building and revolutionising ideas around the way products and product parts could work if they were not limited by manufacturing technology.
3D printing of metals: difficulties and risks
Could this be a perfect manufacturing revolution?
Let’s not go that far. Enthusiasm around novelty methods often creates a situation where risks and limitations are downplayed. 3D printing deserves most of the praise it receives, but it also has its own difficulties and risks, which can, of course, be controlled.
The raw material used for printing is metal powder that is finer than wheat flour. The average particle size is under 50 micrometres. Even though the used metals are non-toxic, in such fine powder form they can end up deep in the respiratory tract and pass through normal clothes and get to the skin or even through the skin. Employees dealing with the powder and pieces must use protective clothing and breathing protection. In addition, metal powder floating in the air could cause a dust explosion the same way that wood dust and powder can.
Must be handled in airtight devices
HT Laser is a pioneering Finnish company in 3D metal printing that won the National Entrepreneurship Award in October. At the beginning of 2019, the company launched a metal printer with two 700-watt lasers at its Keuruu plant.
A three-compartment unit with separate ventilation was built at the factory for carrying out the printing. One compartment is for handling the powder, another for printing, and the third for the post-treatment of printed objects. The powder and unfinished pieces are always processed in airtight devices.
Gas plays an important role in the printing. The actual printing takes place in a protective atmosphere, and also the powder is kept in a protective atmosphere. Right from the beginning, the gas company Linde (formerly AGA) has acted as a partner in the design and production of systems for handling the gas and powder. Linde was already skilled regarding systems required by the printer model. Linde is able to supply gas and powder processing systems to all printer brands on the market.
HT Laser was founded thirty years ago to supply clippings that were optimised and refined according need to a number of engineering companies. At the time, HT Laser was a pioneering company in Finland in the field of laser and water cutting. HT Laser was also one of the first companies to offer laser welding.
‘Now we are in the same situation with 3D metal printing’, says Sanna Teiskonen, Business Director and Co-Owner of HT Laser. ‘We will be able to deliver the benefits of the new method to a large number of interested customers.’
In the autumn of 2018, HT Laser made the decision to purchase a 3D metal printer, and by the end of the year, the machine itself and related equipment were ready.
The company prepared very carefully for the new technology. Already a couple of years before the investment, the company established a 3D academy, where staff from all sections could learn about the possibilities and requirements of the method.
According to Teiskonen, it was noteworthy how much preparation was required in order to start printing. The company had never handled powder or gas on such a large scale and it was important to handle them with utmost care, as they are a critical element regarding occupational safety.
In Finland, the majority of engineering companies interested in printing rely on the expertise and services of around five Finnish subcontractors. HT Laser stands out in relation to its competitors because of its size. HT Laser manufactures components and assemblies in seven locations in Finland, and in Poznan, Poland. Their production technologies include, for example, laser welding with a robot, which is ideal for welding printed components together. According to Sanna Teiskonen, the company is in an excellent position to offer products where the printed component is part of a larger entity.
Solid material could be cheaper
HT Laser prints aluminium, stainless steel, tool steel, titanium and nickel-based superalloys.
According to Teiskonen, when designing a 3D printable piece, some aspects need to be considered differently compared to other processes. One such aspect is the material.
‘With 3D printing, it is possible to optimise the shape of the part completely regarding its strength and functional requirements. The stronger the material, the less it will wear. Lightening as well as surface shapes and perforations make the product cheaper and not more expensive, as is the case with mechanising’, says Teiskonen.
‘The larger the object the more it costs. The shaping itself is free.’