The seven process families of additive manufacturing

01

Why taxonomy matters

A useful taxonomy tells you what physical event creates the part. Marketing names often emphasize a vendor, a laser, or an application, but the process category reveals the core relationship among feedstock, energy, motion, and consolidation. ISO/ASTM 52900 provides the shared vocabulary used by standards bodies and much of industry ¹. That language lets a buyer compare unlike machines without assuming that every powder system, every resin system, or every extrusion system behaves alike.

The categories are broad. A process family does not specify material chemistry, machine size, atmosphere, parameter window, accuracy, surface condition, or qualification level. Think of the family as the first branch in a decision tree. The next branches are material class, specific process variant, machine capability, post-processing chain, and application requirements ².

02

Extrude or jet material

Material extrusion selectively dispenses material through a nozzle or orifice. The familiar desktop form melts thermoplastic filament, but the category also includes pellet systems and paste extrusion for clay, food, silicone-like formulations, and cementitious mixtures. Its advantages include accessible equipment, direct material placement, and scale flexibility. Its constraints can include bead geometry, direction-dependent bonding, start-stop artifacts, support needs, and sensitivity to rheology or thermal history.

Material jetting selectively deposits droplets of build material, often using arrays of inkjet-style nozzles. Droplets may be cured or solidified after placement. The process can produce fine features, smooth surfaces, and multiple colors or material-like properties in one build. Tradeoffs include material-system restrictions, support removal, operating cost, and the fact that a visually realistic polymer model is not automatically a durable engineering component.

• Material extrusion: a material bead is placed where geometry is needed.
• Material jetting: discrete droplets of build material are placed selectively.
• Both require attention to deposition consistency, support strategy, and interface quality.

03

Cure liquid or consolidate powder

Vat photopolymerization selectively cures regions of liquid photopolymer in a vat using light. Laser-scanned stereolithography, masked-layer systems, and projection systems sit within this family. It is valued for fine detail and smooth surfaces, but parts usually need washing and secondary curing. Uncured resin exposure, contaminated waste, cure depth, support placement, shrinkage, and long-term material behavior are part of the process—not cleanup trivia.

Powder bed fusion uses thermal energy to selectively fuse regions of a powder bed. Depending on the variant, the feedstock may be polymer or metal, and the energy source may be a laser, electron beam, or another thermal system. Unsintered powder can support surrounding geometry in some polymer workflows, while metal systems commonly need supports for anchoring and heat management. Powder condition, atmosphere, thermal gradients, depowdering, and downstream heat treatment can strongly influence outcomes ³.

04

Bind powder or feed a melt pool

Binder jetting selectively deposits a liquid bonding agent onto a powder bed. Many metal and ceramic binder-jetted parts are cured and depowdered, then densified by sintering and sometimes infiltration; sand molds, cores, and other binder-jetted products use different finishing routes ⁵. Because the binder placement stage does not have to melt the entire build locally, it can offer high throughput and broad material possibilities. In sintered routes, the important dimensional story often happens later: binder removal and sintering can cause material-dependent shrinkage that must be predicted and controlled ⁵.

Directed energy deposition uses focused thermal energy to fuse material as it is deposited. Powder or wire enters a melt pool created by a laser, electron beam, or arc. DED can add material to existing components, create near-net shapes, and support repair or feature addition. It generally produces coarser geometry than fine powder-bed systems and may require machining. Thermal management, shielding, path planning, dilution with the substrate, and inspection are central concerns.

• Metal and ceramic binder-jet routes commonly separate selective binding from later densification.
• Directed energy deposition creates and moves a localized fusion zone while feedstock arrives.
• Neither process is adequately described by layer thickness alone.

05

Join sheets—and compare responsibly

Sheet lamination bonds sheets of material to form a part. Layers may be cut before or after bonding, and joining mechanisms can include adhesive, heat, or ultrasonic welding. Paper-based systems can make visual models; ultrasonic consolidation can join thin metal foils and may embed components. Material interfaces, trapped voids, cutting access, waste from surrounding sheet, and the properties across bonded layers must be understood for the specific variant.

A fair comparison begins with requirements, not superlatives. Ask about compatible feedstock, build envelope, feature scale, dimensional capability, surface condition, internal geometry, support or powder removal, throughput, post-processing, facility hazards, data traceability, and inspection. NIST’s qualification work underscores why geometry, defects, anisotropy, residual stress, and post-processing must be evaluated together ⁴. A process that is ideal for a dental model may be wrong for a hot structural bracket or a meter-scale wall.

• Compare complete process chains, including cleanup and post-processing.
• Separate nominal machine settings from measured part performance.
• Match evidence and controls to the consequence of failure.
• Expect hybrid workflows when one process cannot satisfy every surface and interface.