- Direct metal laser sintering (DMLS), closely related to called selective laser sintering (SLS), is a type of 3D printing employed for both mass production of metal parts and rapid prototyping
- Selective Laser Sintering and Direct Metal Laser Sintering are basically the same. The difference is that the term SLS refers to the process as applied to an assortment of materials, including ceramics, plastics and glass, while DMLS refers to the process as it is applied to metal alloys
- The way it works, the printer’s hopper is loaded up with metal powder; the heaters will then get the powder up to a temperature close to the sintering range of the alloy.
- Next, the build starts as a thin layer of metal powder is dispensed onto the build platform- the laser then starts its path for this layer, selectively sintering the powder until it transforms into a solid
- Finally, after the part cools, the loose metal powder is removed from the printer.
- Advantages include the ability to create metal parts directly; the ability to use a variety of materials including titanium, cobalt chrome, precious metals and more; very strong parts; the unused metal powder is recyclable
- Disadvantages include expensive price points, both the printers and materials are pricey; the parts tend to be porous; small build volumes
What is Direct Metal Laser Sintering (DMLS)?
Direct Metal Laser Sintering, or DMLS, is a metal fabrication process that is based on additive manufacturing technology.
This process was first developed in the early 80s to allow for a wide variety of metal parts to be 3D printed without the need for sophisticated or expensive tooling or assembly.
DMLS allows for the fabrication of any shape from metal powders by using an array of laser beams to melt and fuse powder particles together.
This technology has been widely adopted by many industries and sectors and is currently being used for applications in the Aerospace, Automotive and Medical industries.
This article examines the benefits of this manufacturing process and the current limitations of Direct Metal Laser Sintering (DMLS) technology.
What are the steps involved in the Direct Metal Laser Sintering (DMLS) process?
Parts created using the Direct Metal Laser Sintering (DMLS) technology are made from a bed of metal powder by repeatedly building up layers with the laser beam.
As more layers are added and areas cooled, the support material is applied until the next layer is built up. The layers gradually grow as more layers are added and cooling pellets are used as a temporary support material until the next layer is built up.
This process is repeated until the end of the part is reached. The part is then assembled by using special tools or a mechanical solution
Fabrication Process Details
The DMLS fabrication process is carried out within a specially designed processing chamber that houses a variety of powder feeding, melting, fusing and post-processing equipment.
The chamber is designed to integrate, guide and focus a series of laser beams onto the powder feed, which can be produced from various powders, ranging from steel and aluminum to titanium.
This is achieved by using a series of mirrors and lenses that are strategically placed within the chamber.
The central part of the chamber is divided into sectors where a single output beam can be focused on powder supply devices, thus allowing for multiple machines in the same chamber to fabricate different products using different materials.
During the fabrication process, the two opposing laser beams melt the powder particles together.
The metal powder particles are then attracted to the heated area by surface tension. This allows for a layer of dense metal powders to be deposited on top of each other in one continuous layer.
The continuous layer gradually grows as more layers are added and cooling pellets are used as a temporary support material until the next layer is built up. The DMLS process is capable of creating any shape from metal powders, including complex geometries.
Benefits of Direct Metal Laser Sintering (DMLS)
1. Direct Metal Laser Sintering (DMLS) technology can fabricate any shape from metal powders.
2. The technology is capable of building up parts layer by layer, allowing for the fabrication of near net shape parts.
3. Parts with complex geometries can be fabricated because the Direct Metal Laser Sintering (DMLS) process is capable of creating intricate designs that include internal and external features as well as holes and channels.
4. The Direct Metal Laser Sintering (DMLS) technology requires little or no tooling, which makes this process the most cost-effective and least labor-intensive of all additive manufacturing processes.
5. The Direct Metal Laser Sintering (DMLS) technology can be used to produce low-volume parts and prototypes that can be made in small batches.
6. Manufacturers can obtain product certification by using the Direct Metal Laser Sintering (DMLS) process.
7. The Direct Metal Laser Sintering (DMLS) process is particularly suited to producing near-net-shape parts with complex geometries, such as those created for Aerospace Industry applications.
8. The Direct Metal Laser Sintering (DMLS) process is less sensitive to environmental conditions than most other processes and materials. This makes the process suitable for use in high-temperature environments and enables parts to withstand extreme heat, cold or water immersion.
9. The Direct Metal Laser Sintering (DMLS) process is versatile because it can be adapted to produce products from multiple materials simultaneously.
10. The Direct Metal Laser Sintering (DMLS) process produces strong, fine-grained metal parts with a smooth surface finish.
Limitations of Direct Metal Laser Sintering (DMLS)
1. Parts produced using the Direct Metal Laser Sintering (DMLS) technology have a rough texture and are usually considered unsuitable for fine or highly detailed printing, such as those used in applications that require close tolerances.
2. The Direct Metal Laser Sintering (DMLS) process is limited in the types of metals that can be processed because the technology works only with powders made of pure alloys with a melting point at or above 900 degrees Celsius.
3. The Direct Metal Laser Sintering (DMLS) process creates parts that are not corrosion-proof.
4. The Direct Metal Laser Sintering (DMLS) process produces heavy parts and the high-temperature processes involved in this metal fabrication technology can create distortion, which makes it unsuitable for use in applications that require a close fit between components areas or require high stiffness.
The Types Of 3D Printing
- Stereolithography (SLA)
- Selective Laser Sintering (SLS): (check out the best SLS 3D printers)
- Digital Light Processing (DLP)
- PolyJet 3D printing
- Multi Jet Fusion (MJF)
- Electron Beam Melting (EBM)
- Direct Metal Laser Sintering (DMLS)
- Binder Jetting (BJ) Technology
- Drop on Demand (DOD)
- Fused Deposition Modelling (FDM)