**3.2 Implant pre-processing**

The planning of manufacturing process of implants in Additive Manufacturing consists of two steps:


Additive Manufacturing Solutions for Improved Medical Implants 157

Once the pre-processing is done, implants are manufactured layer by layer on the machine. In the case of EBM, as mentioned before, the printing of the layers is done by the action of electron beam which performs a selective melting of material (fuses the black part on Figure 10 and leaves unfused the white part). The electron beam is very powerful and has a diameter of approximately 240 microns, which makes the contour of the layer – that is the surface of the implant when finished - a bit rough (Figure 12). This implies additional postprocessing in the zones of the implant that need smooth surface. However, in order to get better surface quality, the technology has suffered some changes recently and a *Multibeam®*

Fig. 12. Multibeam® strategy for better implant surface quality (left), fusing the layer (right)

After the fabrication has finished, the building platform with implants is taken out of the powder bed (Figure 13). Major part of the unfused powder is directly poured into a sifting system and filtered for reuse. However, in the case of EBM, the working temperature of the chamber reaches high value (650ºC for Ti64). Hence, the unfused powder is semi-sintered which is why, in order to clean the implants thoroughly, they are transferred to *Powder* 

Fig. 13. Implant post-processing. From left to right: hip stem still involved by the powder bed; powder recovery system; knee implant as taken out from the machine and after

**3.3 Implant fabrication** 

strategy has been introduced (Figure 12).

**3.4 Implant post-processing** 

support removal and hand polishing.

Fig. 10. Packing of implants for more efficient fabrication.

Fig. 11. One digital layer as represented in EBM Control software (black part is fused and white left unfused).
