Master the most popular metal 3D printing processes for high-end applications.
Direct Metal Laser Sintering (DMLS) and Selective Laser Melting (SLM) are the most used metal 3D priting processes today. They are particullarly suitable for high-end applications as they offer great design freedom & advanced material properties.
In the section, we will dive deeper into the manufacturing process, technical charactereistics and benefits and limitations of these two, very simillar processes.
A DMLS/SLM metal 3D printer in action
DMLS (Direct Metal Laser Sintering) or SLM (Selective Laser Melting) are two powder bed fusion metal 3D printing technologies. The practical difference between SLM and DMLS are very slim. For design purposes, the two technologies can be treated as the same.
They both use a high power laser to bond metal powder particles together to form a part layer-by-layer. SLM achieves a full melt, while DMLS causes the metal particles to fuse together on a molecular level due to the very high temperatures. Most metal alloys are compatible with the DMLS process, while only certain (pure) metal materials can be used in SLM.
Schematic of a typical DMLS/SLM 3D printer
Here are the basic steps of the DMLS/SLM 3D printing process:
The 3D printing step is only the beginning of the DMLS/SLM manufacturing process. After the print is complete, several (compolsory or optional) post-processing steps are required before the parts are ready to use. Compulsory post-processing steps include:
To meet engineering specifications, additional post-processing steps are often required. These may include:
The raw material used in DMSL/SLM and many other 3D printing processes comes in a powder.
The characteristics of the metal powders are very important for the end results. To ensure good flow and close packing, metal particles need to have a spherical shape and a size between 15 and 45 microns. To achieve these tight requirements, methods such as gas or plasma atomization are commonly used.
The high cost of producing these metal powders is a key contributor to the overall cost of metal 3D printing.
The main strength of DMLS/SLM is its ability to create highly optimized, organic structures from high-performance metal alloys.
Parts manufactured with DMLS/SLM can have a complex, organic shape that is optimized to minimize their weight while maximizing their stiffness. Or they can have internal geometries that cannot be produced with any other method.
The material properties of DMLS/SLM parts are excellent. Parts with almost no internal porosity are manufactured from a wide range of metal alloys, from aluminum and steel to high-strength superalloys.
We saw in a previous section though that the costs connected with DMLS/SLM are high. For this reason, it is only economically viable to use this processes for optimized parts for high-value engineering applications.
From a technical perspective, the main limitation of DMLS and SLM is their need for extensive support structures. These are needed to avoid warping and to anchor the part to the build platform. Also, out of the printer, the surface roughness of the produced parts is relatively high for most engineering applications, so post-processing is necessary.
The table below summarizes the basic technical capabilities of a typical DMLS/SLM metal 3D printer today. For additional design guidelines, jump to the design rules.
|Material selection||Large range of materials currently available
Aluminum alloys, titanium, stainless steel, tool steel, cobalt-chrome alloys, nickel superalloys, precious metals etc.
|Dimensional accuracy||± 0.1 mm|
|Typical build size||250 x 150 x 150 mm
(up to up to 500 x 280 x 360 mm)
|Common layer thickness||20 – 50 μm|
|Typical surface roughness||RA 8 - 10 μm|
|Internal porosity||Less than 0.2 - 0.5%|
|Cost per part||$$$$$|