Selective Laser Melting (SLM)

Powder bed fusion is the leading technology in the precision manufacturing of geometrycally complex metal components.

There are different processes depending on the heat source used (laser beam or electrons), and on the material melting degree (sintered or fusion).

The most widespread process to manufacture metal parts is the so-called selective laser melting or SLM. It is also known as DMLS (Direct Metal Laser Sintering) or Laser Cusing.

The process starts by creating a three-dimensional model (3D) using computer-assisted design (CAD) software. This 3D model is saved as a STL format file, which is the triangulated representation of the model. Then, the software divides the file data into individual layers and they are sent to the SLM equipment.

In the configuration of a SLM machine, a (laser) heat source selectively melts a layer of powder, previously deposited in very fine, even layers (the layers indicated in the 3D) on a platform, generating the contour and interior of the part. This building platform descends, in z-axis after each layer, by a distance equal to the layer thickness (normally between 20 and 50 microns), an action that is repeated until the part is completed.

After building the part, and depending on its application, finish enhancement activities and/or thermal treatments may be needed to improve the mechanical properties.

Currently, materials such as stainless steel, tool steel, titanium alloys, nickel-based alloys, and aluminium alloys, among others, can be processed by SLM.

Densities of over 99.9% are often achieved, with a surface finish of around 4-10 μm. Therefore, this technology is very useful to manufacture final parts with very complex shapes and structures, with thin walls and/or hidden cavities or channels.