Laser Powder Bed Fusion (LPBF), Directed Energy Deposition (DED) and Hybrid DED, Atomization and Spheroidization, Binderjetting, Direct-Write printing, Additive Friction Stir Deposition (AFSD), Fused Deposition Modeling (FDM), Stereolithography (SLA)
Additive manufacturing may sound complicated, but the theory isn't. Instead of building a sandcastle by subtracting sand away from a pile until the structure appears, imagine adding sand beginning at the bottom and moving up layer by layer until a castle is built. In the actual application of additive manufacturing, the grains of sand would be placed one at a time in a specific order pre-determined by enhanced computer design. There are several general classifications of additive manufacturing processes. They are generally split along lines of energy source and material source, e.g. laser/friction/arc/etc., and powder/wire/ink/etc. These classifications are outlined in the joint ASTM/ISO standard 52900 Additive Manufacturing General Principles and associated Annexes, although the terminology therein has not permeated the whole field yet. Below is a basic introduction to some, but not all, of these additive manufacturing processes.
Material Extrusion
Material Extrusion is one of the most familiar types of additive manufacturing in the world today. The most common type of extrusion printing is known as Fused Deposition Modeling (FDM), or Fused Filament Fabrication (FFF). It involves feeding a polymer filament through a heated nozzle, then moving that nozzle to create a 3D object with the smooth-flowing polymer, one layer at a time. Imagine a hot-glue gun controlled by a robot. This type of additive manufacturing is so ubiquitous that in normal conversation, any “3D-printer” is typically assumed to be of the FFF type until stated otherwise.
FFF printing is generally sub-divided based on 2 main features, maximum temperature and number of print heads. Higher achievable temperatures on the heated nozzle allow for a wider range of polymers to be printed. Two or more print heads allow for multiple materials to be printed, enabling multiple colors of the same polymer, or even 2 different polymers to be extruded, though typically only one at a time. Other specializations include multi-axis printing, continuous track printing, or specialized fiber-reinforcement heads.
Material Jetting
DIW
Binder Jetting
Sand, metals, polymers, ceramics, basically anything powdered
Powder Bed Fusion
LPBF, EB-PBF, polymer SLS
Directed Energy Deposition
LP-DED, LW-DED, WAAAM
Solid-State Processing
Friction Stir, Cold Spray, all the stuff that’s not supposed to melt or have binders