Stereolithography (SLA) and Selective Laser Sintering (SLS) are actually two very different 3D printing technologies but are often compared when evaluating between which process to pick for rapid prototyping. In this article, we breakdown the main differences between these two fantastic technologies and explore which could be a better fit for your project.
SLA is a Vat Photopolymerization technology that uses UV-sensitive liquid materials called photopolymer resin. The process works by submerging the build platform in a vat of resin. A light source (laser) then selectively traces a shape to cure the liquid resin and form a solid layer. The build platform moves slightly—either bottom-up mainly for desktop SLA printers and top-down for industrial printers—and this process repeats layer by layer until the final part is complete.
SLS is a Powder Bed Fusion (PBF) technology that uses powdered materials like nylon. The process begins by spreading a thin layer of powder across the build platform. A high-powered laser then selectively sinters and fuses the polymer powder to form a solid layer. The build platform is lowered, and this process repeats layer by layer until the final object is complete. Once all the layers have cooled, the sintered parts are separated from the unsintered powder, and the excess powder is cleaned and removed to reveal the final 3D-printed object.
| Stereolithography (SLA) | Selective Laser Sintering (SLS) | |
|---|---|---|
| Build Volume | 800 x 800 x 550 mm | 400 × 400 × 450 mm |
| Typical Tolerance | ±0.1 mm to ±0.2 mm | ±0.3 mm |
| Layer Thickness | 0.05–0.1 mm (50–100 microns) | 0.1 mm (100 microns) |
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| Applications | Rapid prototyping Concept modeling High detailed parts with excellent surface quality Intricate prototypes Dental and surgical models Vacuum casting master models Large enclosures and housings | Rapid prototyping Functional, durable parts End-use applications like jigs and fixtures Low-to-mid volume production Housings for electrical devices |
| Parts Need Support Structures | Yes | No |
| Require Escape Holes | Yes | Yes |
| Materials | UV-Sensitive Resin (standard, ABS-like, transparent, high-temperature, etc.) | Thermoplastic powders (PA12, glass and carbon-filled nylon, PP, TPU) |
| Equipment Costs | Desktop printers: $200 to $5,000 Industrial printers: $65,000 to $250,000 | $75,000 to $650,000 |
| Material Costs | $6–$150+ per kilogram (depending on resin type) | $20 to $80+ per kilogram |
| Minimum Feature Size | 0.3 mm (0.5 mm recommended) | 0.5 mm (0.75 mm recommended) |
| Minimum Wall Thickness | 0.2 mm (0.5–1.0 mm recommended) | 0.8 mm (1.5 mm recommended) |
| Minimum Escape Hole Diameter | 3 mm (3.5 recommended) | 3.5 mm (5 mm recommended) |
| Design Guidelines | View SLA Design Guide ↗ | View SLS Design Guide ↗ |
When it comes to fine feature details, SLA has a higher resolution than SLS. This is because the light source or laser has a smaller spot size and can be precisely controlled, making SLA capable of achieving layer resolutions as fine as 25 microns and layer thicknesses as low as 10 microns, resulting in smoother, more detailed surface finishes that resemble injection moulded parts. In comparison, SLS typically achieves minimum layer resolutions of around 60–120 microns, with powder particle size further limiting fine-feature detail and surface finish.
With stereolithography, you have a much wider selection of materials to choose from, including standard resins, ABS-like resins, transparent resins, rigid resins, high-temp resins and more. While SLS is more limited in this regard, it uses engineering-grade polymer powders like Nylon 12 (PA12) with excellent mechanical properties superior to most SLA resins. SLS is also compatible with a other materials like TPU elastomers, polypropylene (PP) and glass- or carbon-filled nylon composites.
Print size can vary quite significantly between both technologies. At HLH, we use SLA printers that can handle much larger single-part builds (up to 800 x 800 x 550mm) than SLS (up to 400 x 400 x 450 mm). However, if your project involves smaller parts in larger quantities, SLS 3D printing is often the more efficient option. As SLS requires no support structures, parts can be strategically nested not only across the X and Y axes but also vertically along the Z-axis, which is not possible with SLA. This allows for maximum usage of the build volume and greater efficiency, making SLS ideal for mid- to higher-volume batch production.
The cost of high-end SLA and SLS printers can vary significantly. SLA offers a wider variety of printer sizes and models, whereas SLS machines generally have more standardized build volumes. You can expect entry-level or desktop SLA printers range between $200 to $5,000, while industrial-class SLA machines can start at $10,000, with larger-format systems ranging from $65,000–$250,000 or more. In contrast, industrial SLS printers typically cost between $75,000–$650,000, with more focus on durable, functional parts and large-volume production.
SLA parts are generally cheaper and have a lower average cost for quick prototypes than SLS. In terms of material costs, SLS PA12 powder typically range from $20–$25 per kilogram in China and $30–$80 or more per kilogram in the US and Europe. SLA resins generally range from $6–$20 per litre for standard resins, $20–$50 per litre for ABS-like/engineering resins and $60–$150 per litre or more for more specialty and more recent high durability resins.
Surface quality and post processing differences is another key distinguishing factor between SLA and SLS printing. The sintering process intrinsically creates a porous solid material, as the air originally within the powder goes to create microscopic air bubbles on the sintered material. Although this is nothing you can see with your naked eye, unlike SLA components, SLS parts feels slightly rough to touch. This means that a much greater post processing effort is needed to achieve certain surface textures and quality.
Stereolithography parts are widely known for being more brittle and less robust compared to other 3D printing technologies like SLS. Although an increasing number of engineering-grade resins have been developed, enabling SLA parts to be used in more end-use applications today, their UV-sensitive resin means they will degrade over prolonged periods when exposed to UV radiation or direct sunlight, eventually becoming brittle and losing their mechanical strength. SLS, on the other hand, produces parts from engineering-grade polymers such as PA12, which are much more durable, impact-resistant, and stable over time, making them better suited for functional and structural applications.
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When deciding between SLA or SLS 3D Printing, certain considerations like strength, resolution or part size may make the decision for you. Use the Table and Comparison Guide above to help narrow down your decision. For expert advice or if you are ready to get a quote, submit your CAD drawing in STL file format to our ‘get-a-quote’ form, and we’ll get back with a quote within 24 hours or less.
