SLS vs. SLM: Key Differences and How to Choose the Right Process

SLS and SLM are nearly-identical AM processes. They utilize similar technology, so are both expensive when compared to other AM processes. Both SLS and SLM produce parts that have equivalent properties to parts made through traditional methods such as injection molding or CNC machining. Therefore when picking between SLS and SLM, consider the final application of the part to be printed and whether plastic or metal would have better performance.

SLS vs. SLM: Technology Comparison

Technology refers to the equipment and tools used to produce a part. Both SLS and SLM systems have similar complex technologies and processes. They use high-powered lasers, thermoplastic or metal powders, and specialized 3D-printing environments. The primary differences between the two forms of AM as it relates to technology are the addition of gas and the need for a special printing environment for SLM processes.

SLS vs. SLM: Material Comparison

SLS prints parts from thermoplastic powders such as Nylon 11, Nylon 12, and its derivatives. SLM prints parts from pure metal or alloys. While nylons are predominantly used in SLS, the possible materials that can be used with SLM are much more extensive.

SLS vs. SLM: Product Applications Comparison

Possible product applications of SLS vs. SLM depend on whether a thermoplastic or metal part would be more ideal. While both AM methods can provide parts that are environmentally stable, deciding between the two ultimately comes down to two factors: load bearing and weight. SLM may be the better option if higher loads are exerted on the parts. If light weight is more critical, SLS may be better.

SLS vs. SLM: Print Volume Comparison

The print volumes for SLS and SLM are similar since the two AM methods are nearly identical. SLS printers can have print volumes up to 550 x 550 x 750 mm while SLM printers can have volumes up to 350 x 350 x 350 mm. There isn’t a substantial difference in print volume between the two.

SLS vs. SLM: Surface Finish Comparison

SLS printers produce parts with excellent surface finishes, but sometimes leave surfaces feeling  grainy and powdery. Surfaces can be post-processed with blasting media such as: water jet or sand, spray painting, or lacquering. SLM printers can produce metal parts with exceptional surface finishes that seldom require post-processing. SLM parts can be post-processed to increase corrosion resistance.

SLS vs. SLM: Cost Comparison

Because both SLS and SLM systems use complex, advanced technologies, they can be expensive. SLS systems start as low as $18,000 and can go as high as $100,000. SLM printers are more costly. They range from $55,000 to $350,000. 

What are the Mutual Alternatives to SLS and SLM?

There are no mutual alternatives to both SLS and SLM printing methods. This is because one produces thermoplastic parts and another produces metal parts. However, for each case, alternative processes do exist.

What are the Similarities Between SLS and SLM?

Similarities between SLS and SLM include:

1. Both SLS and SLM use a laser and a powdered material to produce parts.
2. Both SLS and SLM are excellent for prototyping and proof-of-concept.
3. Both SLS and SLM can rapidly produce parts for low-volume production.
4. Both SLS and SLM can produce parts with complex geometries.

What are the Other Comparisons for SLS Besides SLM?

Besides FDM, other comparisons for SLS include:

1. SLS vs. MJF: Multi Jet Fusion (MJF) is comparable to SLS because both methods use a powder and a fusing mechanism to build parts. There are two main differences between SLS vs. MJF, however. The MJF process uses ink agents and infrared frequencies to solidify parts. It can also print much faster than SLS since entire layers are heated at once, rather than particular areas of the build platform in SLS. To learn more, see our full guide on SLS vs. MJF.
2. SLS vs. SLA: SLA is a comparative alternative because it can be used for both functional prototypes and production. The difference between SLS vs. SLA is that SLA has an even greater resolution than SLS. It offers the highest resolution out of any form of AM and therefore can also be used for molds, tooling, patterns, and textures. To learn more, see our full guide on SLS vs. SLA.

What are the Other Comparisons to SLM Besides SLS?

Other comparisons to SLM besides SLS include:

1. SLM vs. DMLS: Direct metal laser sintering (DMLS) is comparable to SLM because both methods utilize a metal powder to produce parts. The main difference between SLM vs. DMLS is that in DMLS, metal powders are sintered, rather than melted – similar to SLS processes for thermoplastics. DMLS printers cannot achieve the same level of resolution as SLM since metal powders are not melted and homogenized into the structure. To learn more, see our full guide on DMLS vs. SLM.
2. SLM vs. EBM: Electron beam melting (EBM) is another comparison to SLM. The difference between SLM vs. EBM is that rather than using a laser to melt powders in SLM, an electron beam is used in EBM. EBM produces parts that are of similar resolution to SLM equivalents. However, only a select few metals, like titanium alloys, can be used. To learn more, see our full guide on EBM vs. SLM.

Frequently Asked Questions About SLS and SLM

How are SLS and SLM similar?

These two printing types are similar in that they both use high-powered lasers to create layers and, thus fully made parts. They’re both great methods for prototyping and can both quickly and efficiently print products—even with complex designs.

What are the costs of SLS vs SLM?

Both 3D printing methods can be pretty expensive due to the technology and type of machinery needed. That said, SLS printers tend to be slightly less, ranging between $18,000 and $100,000, whereas SLM machines range between $55,000 to $350,000.

Kat de Naoum

Kat de Naoum is a writer, author, editor, and content specialist from the UK with 20+ years of writing experience. Kat has experience writing for a variety of manufacturing and technical organizations and loves the world of engineering. Alongside writing, Kat was a paralegal for almost 10 years, seven of which were in ship finance. She has written for many publications, both print and online. Kat has a BA in English literature and philosophy, and an MA in creative writing from Kingston University.

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