Additive manufacturing (AM) creates a part by adding material according to a digital geometry rather than removing material from a larger workpiece or filling one complete mould cavity.

The defining idea is layerwise or locally accumulated material placement, but different AM families realize it with very different physics.

Representative families include:

• material extrusion: softened material is deposited through a nozzle;
• vat photopolymerization: light selectively cures regions of liquid resin;
• powder-bed fusion: thermal energy selectively fuses regions of a powder layer;
• binder-based processes, where a liquid binder joins powder before later consolidation;
• directed-energy deposition, where feedstock and energy are delivered together to a local melt region.

These processes share digital geometry but not identical material behavior, accuracy, support needs or production economics.

AM process selection therefore considers:

• material availability;
• minimum feature and layer scale;
• surface quality and dimensional accuracy;
• support or powder-removal requirements;
• build rate and build volume;
• anisotropy and defect sensitivity;
• postprocessing needs.

AM is especially valuable when geometric complexity, customization or low tooling investment matters. It does not make manufacturing constraints disappear; it replaces one set of constraints with another determined by layer creation, energy/material delivery and postprocessing.