Key Words: EBM, Design Freedom, Building without Support structures

EBM: Increasing Design Freedom and Reducing Defect Density

Electron Beam Melting (EBM) is a powder bed based Additive Manufacturing (AM) process, which does not require any support structures. EBM builds components layer by layer from bottom to top using metal powder. Different from any other AM process, EBM has a unique preheating routine. Not only does preheating occur from the top, but every single layer is preheated before being selectively melted by an electron beam under vacuum. As a consequence of this layer wise preheating, the powder layers are sintered. Sintering is a thermal treatment for bonding particles into a coherent, predominantly solid structure via mass transport. This bonding leads to improved strength. Hence, the sintered powder layers are able to carry loads. Overhanging structures can, thus, be printed without the help of support structures increasing the design freedom of AM.

In comparison, support structures are frequently used in Laser Powder Bed Fusion (LPBF). However, they affect the final microstructure of the part and increase post processing effort, since they need to be removed. Components, like the bearing cage with overhanging structures shown above, cannot be built with LPBF without support structures. The sintered powder layers also allow stacking of components.

Depending on size and geometry, hundreds of components can be printed within one job; reducing the unit price significantly. Furthermore, the post processing of the components to improve surface finish can be combined with the removal of the sintered powder. In addition, EBM uses a larger powder particle size distribution and thicker powder layers, which considerably increases the build rate. Moreover, the heat dispersion of metal powder is improved by the sintering, therefore, temperature gradients throughout the component are lower, reducing distortion and crack density within the part.

The improved design freedom and reduced defect density make EBM especially interesting for the medical, aerospace and automotive industries. With respect to these industries common researched materials include Ti-64, various steels, Ni-Superalloys, copper and Ti-Aluminides. Especially electro mobility poses a promising research field in terms of materials used and products for the Chair for Digital Additive Production DAP