SLS vs SLA in 3D Printing. What Is the Difference?

by Mike Brooks | Last Updated: May 2, 2022

3D printing technology provides professionals and hobbyists with different printing methods.

SLS vs SLA

One such method is stereolithography or SLA printing. SLA printing technology uses a single laser beam directed at a particular point to cure the liquid resin.

Healed resin results in the solidified designated 3D object.

In SLS or Selective Laser Sintering, the machine projects a laser beam that fuses or sinters the powder together to form the intended 3D printed part.

SLS vs SLA in 3D Printing

The SLA and SLS 3D printing technology belong to additive manufacturing technology. However, SLS belongs to the powder bed fusion family, while SLA relates to the liquid resin family.

Another distinct difference is that SLS remains tougher and lower in costs to SLA. However, SLA produces 3D objects with tighter dimensional tolerance to SLS.

Also, SLA technology produces 3D objects with an excellent surface finish synonymous with injection-molded 3D parts.

The article takes you through comprehensive information on 3D printing technology. More so, the technological differences. As such, you’ll be in a prime position to choose the method that suits your personal 3D printing needs.

The Three Primary 3D Printing Technologies

1. Stereolithography (SLA) 3D Printing Technology

The 3D printing engineers invented SLA printers around 1980. The technology uses a UV-light laser beam in the 3D parts production process.

Notably, the SLA printer uses the laser beam to cure liquid resin during the printing process.

3D printing professionals and hobbyists refer to the SLA printing process as photopolymerization. Once the UV-light laser beam cures the liquid resin, it solidifies, creating the 3D printed part.

Advantages of Stereolithography or SLA Printing Method

Disadvantages of SLA Printing Method

Applications of the SLA Printing Method

The 3D printing fraternity uses Stereolithography or SLA printing technology in numerous applications. More significantly, they use SLA printers when creating functional parts, molds, and patterns in the following industries;

2. Selective Laser Sintering or SLS 3D Printing Technology

Selective Laser Sintering or SLS technologies represents powder-bed additive manufacturing 3D printing process. It is the most popular and predictable additive manufacturing technology for industrial applications.

SLS printers use a UV-light laser beam to melt and fuse powder particles to form a 3D printed part. Significantly, laser power differs from SLS printers. Also, it determines the material type the printers can use.

Advantages of SLS 3D Printing Method

Disadvantages of Selective Laser Sintering or SLS 3D Printing Method

Applications of Selective Laser Sintering or SLS 3D printing Method

SLS technology works best in functional prototyping and the engineering industry. Other applications of SLS printing technology include;

3. Fused Deposition Modeling or FDM 3D Printing Technology

Fused Deposition Modeling or FDM is an additive manufacturing 3D printing process. Importantly, additive manufacturing refers to producing objects by adding layers of materials until production is complete.

FDM is also known as Fused Filament Fabrication. Additionally, it ranks highly among popular 3D printing technologies.

The technology allows different printers to use the same material filament like PLA, ABS, or PETG.

The heated printer nozzle extrudes and deposits these thermoplastic filaments in the printed bed layer upon layer. The molten filament layers cool down to form the envisioned 3D object.

Advantages of Fused Deposition Modeling Technology

Disadvantages of Fused Deposition Modeling Technology

Applications of Fused Deposition Modeling Technology

SLA vs SLS. Let’s See the Differences!

SLA and SLS are additive manufacturing (AM) 3D printing processes. Also, both use a laser to trace and build print layers and need post-processing.

However, they differ in different aspects, and you’ll need to choose the most suitable method for your unique needs.

SLA printers cure liquid resin to manufacture a 3D printed part. Conversely, SLS printers selectively fuse the excess powder in the printing process.

SLA printing technology manufactures parts with tighter dimensional tolerance. On the other hand, the SLS process provides more rigid objects which cost relatively lower than SLA.

Also, the SLA process remains the best option for producing smaller 3D printed parts or features.

SLS’s surrounding powder provides a support structure to the print layers during the printing process. Contrastingly, 3D printing professionals design SLA parts to self-support over the printing period.

Additionally, the SLA process offers the best resolution between the two. Both are almost at par when it comes to print accuracy. However, the SLA process reigns supreme with the print surface.

The SLS process enjoys a better throughput than the SLA. It means SLS can print single large parts or many different small parts at one go.

3D printing hobbyists agree that SLS is better suited to print complex 3D designs. At the same time, They believe SLA is easier to use.

Is SLS Stronger Than SLA?

SLS prints more robust 3D objects than the SLA. Significantly, the SLS printing process works when the SLS printer melts, fuses, and sinters powder using UV light.

The melting and fusing of powdered materials allow the printing of more robust objects.

The functional prototypes manufactured using SLS printers remain more substantial and more flexible. Thus, paving the way for producing solid and flexible industrial application material suitable for mechanical purposes.

By contrast, SLA printing produces 3D objects with highly detailed parts. Also, SLA has 3D printed parts with a smooth and fine surface. However, the object strength remains weaker than the SLS printed parts.

Notably, it doesn’t mean that the SLA printed parts are entirely weak. Depending on the type and amount of resin used, SLA printed parts are substantial but relatively brittle.

Is SLS Stronger Than FDM?

Yes! SLS is stronger than FDM!

You can only print SLS printing using powdered nylon. On the contrary, FDM printing offers a wide range of materials.

In FDM printing, the materials you can use include PETG, ABS, PLA, and Nylon. Additionally, the SLS 3D printed parts remain more robust and durable than the FDM printed ones. It is due to technological differences.

Further, FDM printers produce 3D printed parts when the nozzle extrudes molten filament and deposits the material layer upon layer on the print bed. Eventually, the printed layers bond on cooling but never fuse.

By contrast, the SLS printer melts, fuses, and sinters powdered nylon to create 3D printed parts. In short, fused pieces prove more vital than merely bonded parts.

Moreover, FDM printing nylon is not the best option as nylon warps and shrinks readily when subject to FDM.

You might like: When To Choose Nylon Filament

Is SLA More Robust Than FDM?

SLA and FDM remain popular 3D printing methods for both professionals and hobbyists. Notably, they offer;

However, as a hobbyist or professional, you may want to do an in-depth check for details as it will determine the most suitable 3D printing method between the two.

Generally, FDM filaments range from biodegradable PLA material to tougher impact-resistant Kevlar. It makes FDM versatile for printing prototypes, industrial tools, and features.

FDM is stronger than resin-printed 3D parts. Also, FDM outmatches SLA for impact resistance and tensile strength.

Also, popular plastic filaments like PLA, ABS, PETG, PET, Nylon, and Polycarbonates produce better 3D printed parts than standard resin.

However, note that tough resin remains stronger than these plastic filaments, unlike regular resin.

How SLA Works

Software

SLA 3D printing requires designing a 3D model using CAD technology. CAD files are digital files that represent your intended 3D objects.

Not sure what software to use for 3D printing? Read this article that covers different 3D modeling & slicing software.

SLA 3D Printing Process

The SLA 3D printing process starts when the laser beams the first print layer in the photosensitive resin. The moment the laser hits, the liquid resin solidifies.

The SLA printer has a computer-controlled mirror. This mirror guides the laser to hit the appropriate cross-sections of the already printed layers.

Notably, most SLA desktop printers work upside down. Therefore, the laser points up to the printer bed. The build platform starts slowly and raises as the process continues.

Immediately the printer deposits the first layer; the platform raises depending on the layer’s thickness. Thus, it allows for additional resin flow underneath the printed layer.

The laser beams and solidifies the next cross-section of layers. The printer keeps repeating this process until the completion of the entire object.

Post-processing

As soon as the SLA printer completes printing an object, the build platform raises out of the tank, and excess resin drains out. Then you need to remove the model from the build platform.

After that, wash excess resin and place it in a UV oven for the final curing.

How Does SLS Work?

SLS printing process works using an SLS printer. The printer uses a laser as a source of energy.

SLS Printing Process

The SLS printer disperses a thin layer of powder on top of the build plate. Then it preheats the powder to temperatures below the melting point.

As such, the laser finds it easier to raise the temperature of a specific part of the powder bed as it moves to solidify the print model.

The laser selectively melts powders of plastic material, fusing them into 3D printed parts. The SLS printer uses the Laser Powder Bed Fusion (LPBF), an advanced branch of additive manufacturing technology.

The SLS printer uses data from the CAD model to guide the laser. Notably, the unfused powder supports printing, eliminating support structures. Thus, reducing printing costs.

During printing, the platform lowers by a layer into the build platform. It allows the laser to hit the next printed layer to solidify. The printer repeats this process layer by layer until the SLS printed part materializes.

SLS Cooling Process

When the SLS printer completes printing, the build chamber cools down. The build chamber cools down from inside and outside the enclosure allowing the 3D printed part to realize optimal mechanical properties.

If the model gains requisite mechanical properties, it remains safe from the possibility of warping or shrinkage.

SLS Model Post-processing

You need to remove the 3D printed object from the build platform at the end of the printing and cooling process. Also, clean off any excess powder from it.

Hobbyists can recycle unused or excess powder to minimize wastage and ensure the printing process is environmentally friendly.

Furthermore, you can post-process further SLS printed parts through media blasting or tumbling.

Conclusion

The SLS and SLA 3D printing technologies remain the driving force for most 3D printing benefits and industrial applications witnessed in recent times.

Both methods use laser beam technology. Additionally, the laser technology is accurate and eliminates the need for heaters and hot ends. More so, it prevents object warping.

SLA works with photopolymer resin and not metal. Contrastingly SLS works with some polymers and metals such as steel and titanium.

Michael Brooks is the founder of M3DZone.com. He sees a very bright future for 3D printing that's why his mission is to try and make this easy for everyone. Discover your hidden talent and creativity. You can follow here: Facebook, Twitter & Pinterest.