Figure 1.

Schematic view of AM methods – a) continuous filament writing and (b) droplet jetting;23 c) illustration of the FDM extrusion and deposition process (dashed Z showing the platform travels in Z axis, solid line presenting the nozzle travels);24 d) direct ink jet printing;25 e) generic illustration of wire form AM method employing metal26; f) illustration of the wire fed process of glass;27 g) schematic of EHD printing system;28 e) the principles of the powder bed inkjet 3D printing;29 f) the MJP approach;20 g) schematic diagram of SLS process;30 h) schematic drawing of free‐surface and (i) constrained‐surface SLA system.31