Additive manufacturing processes differ significantly from traditional formative and subtractive processes. Formative processes, e. g. injection moulding or casting, require the initial manufacture of long-lead, high-cost tooling or moulds into which material is injected or poured. Subtractive processes, e. g. milling or turning, typically require the procurement of a long-lead, high-cost forging from which material is removed to achieve the final component definition.

Additive manufacturing processes create components by the selective addition of material layer by layer to form the component geometry. Material is only added at each layer where specified by the computer-aided design (CAD) definition. This fundamental difference can offer a number of business and technical advantages over traditional process.

Additive manufacturing processes are often sub-divided according to the energy source used and/or the raw material delivery method. There are two energy sources widely used in industry; lasers and electron beam. There are also two material — delivery methods: ‘powder bed’ and ‘blown powder’.

The term additive layer manufacturing (ALM) is typically used and should not be confused with rapid prototyping which infers a rapid manufacture that may or may not be correct and an end use for the component.

Laser sintering is an inaccurate and unofficial definition, and should not be used as a description for this technology. Direct metal laser sintering is a registered trademark of Electro-Optical Systems (EOS) GmbH and should not be used, as it would denote a specific vendor, not a technology or process group.

3D-printing is an increasingly common term within the industry. However, it is predominantly used when referring to a much wider group of technologies including polymer-based systems.