SLM™ Technology for 3D Jewellery Production
Introduction of SLM™
Selective laser melting (SLM) is a particularly rapid prototyping, 3D printing, or Additive Manufacturing (AM) technique designed to use a high power-density laser to melt and fuse metallic powders together. Even if SLM is considered by many to be a subcategory of Selective Laser Sintering (SLS),the SLM process, unlike SLS, has the ability to fully melt the metal material into a solid 3D-dimensional part. Since the components are built layer by layer, it is possible to design organic geometries, internal features and challenging passages that could not be cast or otherwise machined. SLM produces strong, durable metal parts that work well as both functional prototypes or end-use production parts.
The process starts by slicing the 3D CAD file data into layers, usually from 20 to 100 micrometres thick, creating a 2D image of each layer; this file format is the industry standard .stl file used on most layer-based 3D printing or stereolithography technologies. This file is then loaded into a file preparation software package that assigns parameters, values and physical supports that allow the file to be interpreted and built by different types of additive manufacturing machines.
With selective laser melting, thin layers of atomized fine metal powder are evenly distributed using a coating mechanism onto a substrate plate, usually metal, that is fastened to an indexing table that moves in the vertical (Z) axis. This takes place inside a chamber containing a tightly controlled atmosphere of inert gas, either argon or nitrogen at oxygen levels below 500 parts per million. Once each layer has been distributed, each 2D slice of the part geometry is fused by selectively melting the powder. This is accomplished with a high-power laser beam, usually an ytterbium fiber laser with hundreds of watts. The laser beam is directed in the X and Y directions with two high frequency scanning mirrors. The laser energy is intense enough to permit full melting (welding) of the particles to form solid metal. The process is repeated layer after layer until the part is complete