Energy and mass transfer in additive manufacturing

Transformation of the material prior to consolidation requires energy input. With the right wavelength, lasers can deliver high power density with high material absorbency. Electron beams used under vacuum for additive manufacturing of metals and metal alloys avoid substrate oxidation and deliver very high power density. Extrusion involves heating the material by thermal conduction using the Joule effect of a heating resistor, and conveying it by applying high shear.

In a material deposition manufacturing process, mass transfer is achieved by extrusion of a molten filament or by droplet projection. Coalescence of the material on the substrate creates a network of pores. In the case of selective powder consolidation, densification by coalescence leads to a local variation in volume density.