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.