SLS vs. DMLS: Differences and Comparison
Learn about the differences between these two 3D printing technologies.
Xometry offers SLS and DMLS, which are both powder bed fusion technologies that create parts via laser sintering. SLS is used to turn plastic powders into parts, whereas DMLS, on the other hand, creates high-performance solid metal parts by sintering together metal powder. SLS is great for affordable plastic printing. DMLS is better for producing items with significantly better mechanical properties, but they come at a much higher cost. As such, DMLS is ideal for functional parts used in extreme environments, whereas SLS can be used for lower-performance functional parts or visual prototypes. Printing speeds are comparable between the two; however, DMLS has more intense post-processing steps that can add lead time to production.
In this article, we will examine the comparison of SLS and DMLS in more detail. We will review their fundamental differences, the materials they work in, and the printing technology itself.
The SLS 3D Printing Process
SLS (Selective Laser Sintering) is a plastic powder bed 3D printing technology that makes use of a sintering process. It was first invented by Dr. Carl Deckard and Dr. Joe Beaman in the mid-1980s. SLS works by selectively sintering a plastic powder with a laser beam (typically a CO2 laser). The powder is heated up close to its melting temperature, and then a laser beam traces out the cross-section of a part layer, sintering the plastic particles together. After each layer, the print bed moves down, and another layer of powder is applied.
Sintering refers to the process of heating the plastic particles to the point where their outside surfaces begin melting. This causes the individual particles to stick together. SLS primarily works with plastic, whereas DMLS works with metal. To learn more, see our guide on What is SLS 3D Printing. One of Xometry's SLS machines can be seen in the image below:
The Advantages of SLS Over DMLS
Listed below are some key advantages when picking SLS over DMLS:
- SLS can produce cheaper prototypes like those used to check product form (i.e., visual properties) and product fit (i.e., interfacing with other components) compared to DMLS.
- SLS parts do not need support when printing. This allows for nested builds where many parts can be printed simultaneously.
- SLS parts can be dyed in various colors and vapor smoothed.
- SLS machines typically have larger build volumes than DMLS machines and can, therefore, make larger components and more parts at once.
The Disadvantages of SLS Compared to DMLS
There are some limitations and downsides between SLS and DMLS; below are the main disadvantages of SLS:
- SLS is limited to working within plastic materials.
- The mechanical properties of SLS printed parts are far less than those of DMLS printed parts, simply because plastics have less superior material properties than metals.
- SLS parts can be more prone to warpage and shrinkage. While DMLS is not immune to these issues, metal parts can typically better handle the stresses that lead to these problems.
The DMLS 3D Printing Process
DMLS (Direct Metal Laser Sintering) is a powder bed fusion 3D printing technology that is used to manufacture metal parts. EOS first commercialized the technology in 1995. The process is similar to SLS printing but with a few differences. It works by selectively sintering a metal or metal alloy powder with a high-powered laser beam (typically a CO2 laser or a fiber laser). The metal powder is pre-heated and the laser beam traces out the part cross-section, sintering the metal particles together. After each layer, the print bed moves down, and another layer of metal powder is applied. DMLS also fills the build chamber with an inert gas to prevent oxidation and combustion during printing. To learn more, see our guide on What is DMLS.
The Advantages of DMLS Over SLS
When choosing DMLS, there are some key advantages it has over SLS:
- DMLS is capable of printing high-strength functional metal parts in a variety of metals.
- DMLS parts have superior durability and mechanical, chemical, and thermal properties compared to SLS parts, thanks to the properties of metals.
- Parts printed with DMLS typically have finer resolution and detail than SLS parts.
The Disadvantages of DMLS
Here are the downsides to bear in mind when considering DMLS:
- From the higher energy requirements of the machines to raw material cost to the other steps involved with the process, DMLS parts tend to be much more expensive than their SLS counterparts.
- Unlike SLS, DMLS parts need support structures during printing. This is due to the increased mass of metal parts and the stresses involved with metal printing.
- DMLS machines typically have smaller build volumes than SLS machines. This means you may be limited to creating smaller components with DMLS.
A stainless steel part printed with Xometrys DMLS service.
| Attribute | SLS | DMLS |
|---|---|---|
Attribute Typical layer height | SLS 100-120 microns | DMLS 30-40 microns |
Attribute Typical tolerance standards | SLS ± 0.015”, or ± 0.002" per inch, whichever is greater * | DMLS +/- 0.005” for the first inch, plus +/- 0.002” for every inch thereafter |
Attribute Typical build volume | SLS 330 x 330 x 508 mm | DMLS 250 x 250 x 250 mm |
Attribute Minimum recommended feature size | SLS 1 mm | DMLS 0.5 mm |
Attribute Parts need support structures | SLS No | DMLS Yes |
Attribute Has isotropic material properties | SLS Yes | DMLS Yes |
Attribute Can print in metal | SLS No | DMLS Yes |
* SLS tolerances listed are for standard nylon 12. Different tolerance standards may apply to different materials.
SLS vs. DMLS - Common Comparisons
We often get asked about the comparisons between DMLS and SLS. In the expandable sections below you'll find the most common comparisons we get asked about between these two processes.
Technology
Fundamentally, SLS and DMLS share the same technology, i.e., powder bed fusion. The difference lies in the power of the laser and the fact that DMLS machines need to have their build chambers filled with an inert gas during printing. DMLS parts must also be attached to the build plate either directly or with support structures.
Materials
Fundamentally, SLS and DMLS share the same technology, i.e., powder bed fusion. The difference lies in the power of the laser and the fact that DMLS machines need to have their build chambers filled with an inert gas during printing. DMLS parts must also be attached to the build plate either directly or with support structures.
Applications
Fundamentally, SLS and DMLS share the same technology, i.e., powder bed fusion. The difference lies in the power of the laser and the fact that DMLS machines need to have their build chambers filled with an inert gas during printing. DMLS parts must also be attached to the build plate either directly or with support structures.
Print Volume
SLS machines typically have a larger build volume than DMLS machines. Some SLS machines that utilize a dual-laser system can print parts around two feet in length! Additionally, since SLS does not require support structures, it means parts can be nested or stacked vertically in the build volume, allowing SLS to potentially print hundreds of components at a time. DMLS, on the other hand, is typically limited to smaller build volumes around a ten-inch cube in size, and each part must be attached to the build plate either directly or with support structures.
Surface Finish
Due to the nature of the sintering process, both technologies will produce parts with a semi-rough/matte surface finish. DMLS parts will naturally have a smoother finish due to the finer layer height the machine prints at. Both technologies can have their parts post-processed to improve surface quality. Typical processes can include tumbling, bead blasting, and polishing, whereas only polishing is possible on DMLS metal parts. SLS parts can also be chemically vapor smoothed to improve surface finish, which is an option Xometry directly offers.
Process Cost
DMLS is significantly more expensive than SLS. This is due to the high cost of the metal powder, high energy consumption, and the more expensive machines used for DMLS printing. When it comes to printing smaller components, SLS can also pack more parts into a single build and require fewer post-processing steps than DMLS, reducing cost further at higher quantities.
Generally, we recommend our customers consider other means of producing metal parts when possible, such as CNC machining. DMLS can be worth it for designs that would otherwise be impossible or inherently challenging to manufacture with conventional methods.
Other Processes You Can Use Instead of SLS and DMLS
Despite the benefits of SLS and DMLS, there are alternative technologies that can achieve similar results:
- Multi-Jet Fusion (MJF): This is yet another powder-bed fusion process offered by Xometry. It is primarily an alternative to SLS since it also works in very similar polyamide materials. Instead of using a laser, the process works more like a traditional ink-jet printer with a printhead that deposits the material and then a fusing agent across the entire build plate in one pass, allowing for the printing of multiple parts simultaneously. It is an excellent process for 3D printing smaller components in production quantities and can be used as a stepping stone to other plastic production processes like injection molding.
- Metal Binder Jetting: On the metal side, we offer the metal binder jetting process. This can be a more affordable alternative to DMLS. Similar to MJF, binder jet machines use a print head to deposit a binding agent to fuse layers of metal powder together. Once this stage is complete, the parts are considered green and left to cure. The cured green parts are then put into a furnace to sinter or be infiltrated with bronze. While this allows for metal parts to be affordably made, the parts are prone to significant shrinkage, are slightly porous, and fine features may not survive due to the furnace sintering process.
How Xometry Can Help
We hope this information helps you make an informed decision on your next 3D printing project. If you need any assistance with which process or material to choose, feel free to contact us; we're happy to help!
Xometry offers automatic quoting on all the processes mentioned in this article. When you are ready for an instant quote, just upload your 3D CAD to the Xometry Instant Quoting Engine® for pricing and lead times.
Disclaimer
The content appearing on this webpage is for informational purposes only. Xometry makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through Xometry’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please refer to our terms and conditions for more information.