SLA vs. SLS 3D printing: What You Need to Know
Stereolithography (SLA) and Selective Laser Sintering (SLS) are two well-known 3D printing methods that use lasers to build objects layer by layer. Although they have some things in common, their methods, materials, costs, and uses are very different.
What Is SLS in 3D Printing?
In the 1980s, Dr. Deckard and Beaman at the University of Texas came up with SLS, which stands for "Selective Laser Sintering." By using a strong laser to join powdered materials like plastic, metal, glass, or ceramic together, this method makes solid parts. The powders that SLS machines usually use are nylon or polymer-based, but more advanced models can handle materials with higher melting points.
The first step in the SLS method is to divide a digital design into thin layers. On a bed of powder, the printer's laser follows each layer, fusing the particles where needed. A new layer of powder is spread over the surface after each layer is finished. This is repeated until the object is fully formed. One great thing about SLS is that it doesn't need any extra support structures during printing. The powder that is still not fused together around the edges of the part supports any parts that hang over. This method is also known for producing parts that last a long time and exhibit good mechanical properties.
However, SLS printers are usually big and require a lot of power, so businesses must spend a lot of money on them. Also, the printing process takes place in a sealed space, so people won’t be able to see the build as it's happening.
What Is SLA in 3D Printing?
Chuck Hull, the founder of 3D Systems, came up with SLA, or stereolithography, in 1986. It is the oldest type of 3D printing. SLA builds things backwards, not forwards, like SLS does. It cures photosensitive plastic into the shape you want with an ultraviolet (UV) laser. It is a printer that submerges the build base in a tank of liquid resin. The UV laser fixes only certain parts of the resin, making them solid. When each layer is dry, the base moves out of the way so that the next layer can be added. This makes it look like the object is rising from the liquid.
Like injection-molded parts, SLA is known for making parts with high precision and smooth surfaces. These printers are usually smaller than SLS machines and can fit on a desk without any problems. But because they are smaller, they can't hold as much, so they aren't as good for making bigger parts. Also, the chemicals used in SLA printing can give off smelly fumes and are bad for the environment, so you need to be careful when handling them. Additionally, SLA parts aren't as strong as SLS parts, which means they work better for prototypes or idea models than for real-life parts.
Similarities Between SLA and SLS 3D Printers
1. Layer-by-Layer Construction
Based on digital 3D models, both SLS and SLA use an additive method to build objects by adding parts one on top of the other. With this method, it's possible to make complicated shapes that would be hard or impossible to make with basic tools and methods.
2. Laser Utilization
There is a laser at the heart of each technology that hardens the material and shapes it into the desired shape. It is a laser that sinters powdered material in SLS and a UV laser that cures liquid photopolymer glue in SLA.
3. High-Resolution Output
Both SLS and SLA can make things with lots of small details and a high resolution. SLA is known for having very high precision and smooth surfaces that look a lot like injection-molded parts. Because it is built on powder, SLS also has a high resolution, but the surface finish may be a little rougher.
4. Support for Complex Geometries
Both technologies can make images that are very detailed and complicated. One advantage of SLS printing is that it doesn’t require additional support structures. The unused powder naturally supports any overhanging features during the process. In SLA, on the other hand, support structures need to be added during the printing process to hold up features that hang over. These structures need to be taken away during post-processing.
5. Post-Processing Requirements
After printing, parts made by both SLS and SLA typically require post-processing to achieve the best quality and appearance. If you want SLA parts to be fully stiff, you have to cure them in a light room or oven and then use different tools to remove the support material. SLS parts mostly need to be cleaned to get rid of extra powder.
Differences Between SLS and PLA
1) Material Types
SLS uses powdered materials like metals, thermoplastics, glass, and pottery. Solid-Liquid Attachment (SLA) utilizes liquid photopolymer resins that harden when they come in contact with a UV laser.
2) Printing Process
In SLS, a laser carefully melts powdered material to make each layer. The powder that isn't melted supports structures that are on top of other layers. If you want to do SLA, you put the build platform in a resin tank and use a UV laser to cure the resin layer by layer.
3) Support Structures
During printing, SLS doesn't need any extra support structures because the surrounding powder that hasn't been heated up holds any features that hang over. For SLA, support structures must often be added during the printing process to hold up features that hang over. These structures must then be taken away during post-processing.
4) Surface Finish and Resolution
SLA parts often have better clarity and smoother surfaces, making them look a lot like injection-molded parts. Because the process is based on powder, the surface of SLS parts may be a little rougher.
5) Strength and Durability of the Part
Most of the time, SLS parts are stronger and last longer, making them good for useful prototypes and final products. Even though SLA parts have a lot of detail, they are more fragile and work better for visual models.
6) Size and Price of a Printer
In terms of both initial investment and ongoing costs, such as higher energy use, SLS machines are bigger and cost more. SLA printers are smaller and less expensive, so small businesses and individuals can use them.
7) After processing
With SLA parts, you have to post-cure them and take off the support structures. For SLS parts, you just have to clean them up and get rid of the extra powder.
8) Build up volume
A normal build volume for an SLA printer is 250x250x250mm, but some models can go as high as 380x380x250mm. SLS printers, on the other hand, can make bigger parts. Their build sizes range from 550x550x750mm to 700x580x380mm.
9) Thin Walls
When set to a high density, SLA printers can make parts with walls as thin as 0.2 mm. Walls that are between 0.6 and 0.8 mm thick are common for standard SLA printers. Most SLS printers need walls that are at least 0.8 mm thick.
10) Holes
In high-resolution settings, SLA printers can make holes as small as 0.5 mm across. In normal settings, they can make holes that are 0.8 to 1.0 mm across. SLS printers can make holes that are between 0.8 and 1 mm in diameter.
11) Clearance Space
In high-resolution settings, SLA printers require at least 0.4 mm of space between parts to prevent them from fusing together during printing. Standard SLA printers need at least 0.6 mm of space. SLS printers can work with gaps as little as 0.3 mm wide.
Best 3D Modeling Software
There are many 3D modeling software available, but we recommend using SelfCAD. It is an easy to use program ideal for users of all levels. It comes with various tools like freehand drawing and sketching, image to 3D model, powerful 3D sculpting brushes, and various modification and deformation tools. The software also comes with many interactive tutorials that you can use to learn how the software works. The video below demonstrates how the software works.
SelfCAD also comes with an in-built online slicer that you can use to slice your files and generate the G-code to send to your 3D printer.
Conclusion
Because it can work with a lot of different materials and make strong parts, SLS is great for making functional prototypes, complicated geometries, and small to medium-sized production runs. Industries that use it a lot include aerospace, automotive, and medical device making.
SLA works best for making parts with very tight tolerances, samples with smooth surfaces, and models with a lot of detail. It's used a lot in fields like medicine, jewelry making, and product design.
It's important to note that SLS and SLA both use lasers to build things one layer at a time, but their materials, methods, costs, and possible uses are very different. It's important to know these differences in order to choose the right 3D printing technology for specific projects.