DMLS vs. SLM: Differences and Comparison
Learn about the differences between these two 3D printing technologies.
DMLS (Direct Metal Laser Sintering) and SLM (Selective Laser Melting) are two very similar powder bed fusion (PBF) technologies. Each technique melts a specified pattern of metal powder using laser beams. By repeating this process in successive layers, the machines build up complex parts, often using advanced metal alloys. DMLS is a trademark of EOS while SLM is a trademark of SLM Solutions. Both technologies fully melt metal powder instead of sintering it the way most metal 3D printing technologies do.
This article will compare DMLS vs. SLM in terms of their strengths and weaknesses, materials, and printing technology.
DMLS Definition and Comparison to SLM
DMLS is a powder bed fusion 3D printing technology that is used to manufacture metal parts. The EOS company owns the trademark and first commercialized the technology in 1995. DMLS is often referred to as a sintering technology, and indeed, the first generation of DMLS machines did only sinter the metal. According to EOS, however, DMLS is a German acronym (Direkt Metall Laser Schmelzen) that more properly translates as melting rather than sintering. The modern printers do fully melt their metal powder, thus creating stronger parts.
This process works by selectively melting a metal or metal alloy powder with a high-powered laser beam (typically a fiber laser). The laser beam traces out the cross-section of each layer and melts the metal particles together. After each layer, the print bed moves down and another layer of metal powder is applied. While printing, the DMLS build chamber is filled with inert gas to prevent oxidation.
For more information, see our guide on DMLS 3D Printing.
Advantages and Disadvantages of DMLS Compared to SLM
Listed below are some key advantages of DMLS vs.SLM:
- The tightly focused DMLS laser creates highly accurate, detailed parts.
- DMLS can accept a wider range of materials than SLM.
Listed below are some key disadvantages of DMLS vs.SLM:
- DMLS prints slower than SLM because it operates at lower power and uses fewer lasers.
- The lower-powered DMLS lasers can only create small melt pools so they cannot print thick layers.
SLM Definition and Comparison to DMLS
Selective laser melting is a powder bed fusion 3D printing technology that is used to manufacture metal parts. Like DMLS, SLM debuted in 1995. It was ultimately commercialized by a company called SLM solutions. SLM uses a laser to selectively melt the metal powder. The laser is high-powered, so it very quickly liquifies any metal powder it contacts. The laser beam traces out the part’s cross-sectional layer, melting metal particles together as it goes. After each layer, the print bed moves down and another layer of metal powder is applied. The SLM build chamber must be filled with an inert gas while it operates. SLM is very similar to DMLS but employs higher-powered lasers. A typical SLM machine is shown in the image below:
A typical SLM machine.
Image Credit: Shutterstock.com/ID1974
Advantages and Disadvantages of SLM Compared to DMLS
Listed below are some key advantages of SLM vs. DMLS:
- SLM can vary its laser size to optimize for either resolution or print speed.
- SLM makes use of multiple high-powered lasers to dramatically improve the speed of printing. The premier DMLS machines make use of only 4 lasers while SLM ones employ up to 12.
Listed below are some key disadvantages of SLM vs.DMLS:
- Because SLM is a higher temperature process, its printed parts often end up with internal stresses.
- SLM machines are designed for high-volume industrial use, so they are extremely expensive.
| Attribute | SLM | DMLS |
|---|---|---|
Attribute Laser point diameter | SLM 80 to 160 microns | DMLS 40 microns (for smaller machines) |
Attribute Number of lasers | SLM Machines with 1, 4, and 12 beams are available | DMLS 4 |
Attribute Variable layer thickness and laser point diameter | SLM Yes | DMLS No |
Attribute Minimum feature size | SLM 140 microns | DMLS 100 microns |
Attribute Has isotropic material properties | SLM Yes | DMLS Yes |
Attribute Parts need to be cooled after printing | SLM Yes | DMLS Yes |
Attribute Parts need support structures | SLM Yes | DMLS Yes |
Attribute Largest print volume | SLM 600 x 600 x 600 mm | DMLS 400 x 400 x 400 mm |
Table 1. DMLS vs. SLM Comparison
Brief Comparisons Along Key Dimensions
Technology comparison: DMLS and SLM are both powder bed fusion technologies that melt the metal powder using lasers. SLM units typically contain higher-powered lasers than do DMLS (1000 watts vs 400 watts). The output power of those SLM lasers can also be varied to alter the part’s detail resolution.
Material comparison: DMLS and SLM can print in a wide range of metals and metal alloys. Typical examples include titanium Ti64, stainless steel 316, and nickel alloys like NI718.
Applications comparison: DMLS is marketed extensively in the medical industry for items such as implants and dental bridges. SLM, on the other hand, serves a broader range of industries such as automotive and aerospace.
Print volume comparison: SLM machines typically have larger build volumes when compared to DMLS. Their multiple lasers also help them exploit the space more efficiently.
Surface finish comparison: Both technologies create similar surface finishes because they operate on the same powder bed fusion principle.
Cost comparison: The manufacturers of both SLM and DMLS offer a wide range of machines. However, the entry-level version of either type typically costs more than $350,000. Because it employs more lasers and can print thicker layers, SLM systems can finish lower-resolution jobs much quicker than DMLS. Faster print time results in lower cost per part.
Alternatives to DMLS and SLM for Your 3D Printing Projects
SLM and DMLS are not entirely unique. There is one alternative technology that can achieve similar results:
- EBM: EBM (Electron Beam Melting) bears similarities to both DMLS and SLM. It is another powder bed fusion technology that uses a beam of energy to melt the powder. However, EBM technology does so using an electron particle beam instead of a laser beam.
Similarities Between DMLS and SLM
Listed below are some of the similarities between DMLS vs. SLM.
- DMLS and SLM both use a laser beam to melt powdered metal.
- DMLS and SLM can use many different metal powders to produce parts.
- Both technologies can employ multiple lasers at once to increase the production rate.
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