How does additive manufacturing work? 3 minutes spent reading

How does additive manufacturing work?

Volkmar Held
As a freelance writer, Volkmar Held reports for voestalpine on topics that move people. The content of his stories ranges from archaeometallurgy to future technologies.

Additive manufacturing revolutionizes the production of highly complex tools and components – or makes their manufacture possible in the first place. This technology perfectly combines the enthusiasm voestalpine has for modern processes with the company’s materials expertise.

Additive manufacturing (AM) has become popular for its manufacturing of plastic models directly from a computer. Since then, the term “3D printing” has become commonly used, although the process has fundamentally changed, especially when it comes to the use of metal raw materials.
With AM, components are manufactured in layers. Depending on the application, various methods may be used. The starting point is always

  • a digital, three-dimensional design that the “printer” can read and implement, as well as
  • metal powder.

Manufactured from the alloys of a wide range of metals, this powder, with grain diameters of about 15 microns (= 0.015 mm) can be thinner than a human hair. The thickness of the required powder depends on the method used, which is selected according to the size of the component, the material and the required precision.
Two different additive manufacturing methods are described in greater detail below.

Laser beam fusion in the powder bed

With laser beam fusion, a component is built up layer by layer from metal powder (grain diameter approx. 15 by 55 microns):

  1. A laser beam fuses the top layer of a powder bed to create the contour of the component. The material solidifies after fusing and forms a solid layer.
  2. The base plate lowers by one layer’s thickness (about 30 to 50 microns) and powder is applied once again.
  3. Again, the contour is fused, whereby the powder grains combine the new layer with the solidified layer below.

This is repeated until the component is completely constructed. In the end, it is encased in unused powder. This can simply be removed, filtered and reused.
Only minimal production advances are needed to enable the manufacture of especially fine structures. This will make it possible to make complicated components that are not producible with other technologies. However, the construction time is longer when compared with conventional methods. Manufacture of an intricately shaped steering knuckle at a size of approx. 15 centimeters currently takes a full 22 hours.

Direct metal deposition (DMD)

Compared to laser beam fusion in the powder bed, the direct metal deposition (DMD) process is capable of working up to 10 times faster and of producing larger components. However, very fine grid structures or component details cannot be achieved with this method – this is already obvious from the grain size of the metal powder used, with ideal particle sizes of 50 to 150 microns (= 0.05 to 0.15 mm), more than three times larger than in laser beam fusion.
For the DMD process – as in laser deposition welding – metal powder is blown into a laser beam, where it is fused and applied in layers. The layer thicknesses are between 0.2 and 0.8 millimeters. Almost all of the powder is solidified in the process. The method is also highly suitable for repairing complex and expensive components, such as in aerospace applications.
The DMD process offers the possibility to manufacture components from various powder materials (multimaterial components) by simply changing the supply tank. Depending on requirements, this can be used to to furnished various sections of the same component with modified material properties, such as with wear-proof surfaces, viscous volumetric properties and corrosion-resistant channels.
In daily production, the DMD process can be combined with removing processes like milling or turning. Hybrid machines enable the manufacture of complex components using additive manufacturing but can also handle highly precise milling jobs in the same setup.

Volkmar Held