Among metal additive manufacturing processes, Selective Laser Melting (SLM) belongs to the powder bed fusion category. Also known as Direct Metal Laser Melting (DMLM), the technique is named after its fundamental mechanism. The process relies on a fine laser beam that is scanned across successive layers of a powder bed to selectively melt intricate tracks. The final components arise from solidification of the melted powder. When compared to other additive manufacturing technologies, this ability to produce high resolution features is one of the reasons why SLM tends to get selected to produce complex components with delicate features.
Practically, a SLM machine comprises
Components have successfully been manufactured out of a wide range of common metallic alloys using DMLM industrial systems (or customisable R&D-focused systems). These materials include aerospace-grade titanium, high strength stainless steels, nickel-based superalloys, cobalt-chrome alloys, lightweight aluminum alloys, and others.
The advantages of SLM over conventional substractive or formative methods are reflected in the following categories:
Shape complexity: it is possible to manufacture virtually any shape. This means that fabricating small lot sizes is economically viable, customized and optimised geometries is possible.
High resolution: material is processed with a fine laser beam, point-by-point and one layer at a time.
Hierarchical complexity: resolution varies with machine capabilities, yet fabricating fines features means that complex hierarchical multi-scale structures can be designed and fabricated in one step with features size spanning the macro- and meso-scale (0.1-10 mm). For instance, lattices can be combined with macrostructures to vary mechanical properties and/or save weight.
Functional complexity: Geometrical flexibility makes it possible to integrate multiple functions in a single component traditionally made out of multiple parts.
Feedstock fluidity and re-usability: In DMLM, unused powder remains fluid and can easy be removed and recycled. Arguably, there still is some confusion about the impact of powder recycling on mechanical properties. Yet, it is a major advantage for parts that require inaccessible internal channels.
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