Direct Metal Laser Sintering (DMLS)
Direct metal laser sintering (DMLS) is one of the few 3D printing technologies that directly create a metal part from its 3D computer model. This process is an advancement of powder metallurgy, a mature metal-moulding technology that uses heat and pressure to form powdered metal parts.
The material used for this 3D printing process is finely powdered metal. Typically the manufactured size of the metal particles is 20 – 40 micrometers. The particle size and shape limit the detail resolution of the final part. Smaller metal particle size and less variation allow better resolution.
Other resolution limits in this technology are the layer height and the size of the laser spot. Like other 3D printing processes, the model is divided into many fine layers, which are then printed one-by-one to build the final part. Printable layer heights are approximately the maximum size of the metal powder used.
To start, the DMLS printer hopper is filled with the desired metal powder. Printer heaters bring the powder to a temperature near the sintering range of the alloy. The printer uses an inert gas, which protects the heated powder and part as it is built.
The build begins with dispensing a thin layer of metal powder onto the build platform. The laser then begins its path for this layer, selectively sintering the powder into a solid. The sequence of dispensing a layer and sintering continues until part completion. After the part is left to cool, the surrounding loose metal powder is removed from the printer. The last steps include support removal as well as any post-processing needed.
Advantages of DMLS
DMLS can produce metal parts directly.
DMLS can be used with metal alloys or pure metals without affecting the properties of the material. Even mixtures of powders (e.g. aluminum and nylon) can be successfully printed.
A wide range of metal and metal alloy powders are available, including steels, stainless steels, aluminum, titanium, nickel alloys, cobalt chrome, precious metals. The properties of a finished part are comparable to a part cast in the same material. Strong, functional metal parts.
Disadvantages of DMLS
DMLS is the most costly of 3D printing processes, equipment and materials are expensive.
DMLS process is slow compared to other processes. Finished DMLS parts are porous relative to a melted metal part. Porosity can be controlled but not eliminated in the process or during post-processing.
Most DMLS printers have small build volumes.