What Is SLA 3D Printing?

by Mike Brooks | Last Updated: June 25, 2022

In 3D printing technology, many different technologies differ in many ways. Some are different in the resin they use, and others in their way of printing. Stereolithography SLA 3D printing is among the major three printing technologies.

SLA 3D Printer

SLA 3D printing is a printing technique that uses the UV laser beam and prints one layer after another. The UV laser moves from one point to another, producing accurate and smooth objects. The technology is best when producing many detailed objects.

There is a lot to learn about the SLA 3D technology, from how it works to its best features and why you should use it and not the other printing technologies. You’ll find all these facts in the article below.

What’s the Meaning of Stereolithography SLA?

An SLA printer is a stereolithography apparatus known as optical fabrication. On the other hand, photo-solidification is a 3D printing technique used to create models, patterns, and prototypes.

The two are additive manufacturing processes that belong to the photopolymerization family. 3D-printed objects are created using the SLA 3D printer technology by curing polymer materials one layer after another using the ultraviolet UV laser beam.

The technology’s research started in the 1970s. Its name came up in 1984, when Chuck Hull applied for a patent. Materials used by the SLA technology include photosensitive thermoset polymers that turn into liquid form.

How Does SLA 3D Printing Technology Work?

Stereolithography SLA 3D systems work by first positioning the build platform in the tank where the liquid photopolymer is located. It’s positioned at a distance of one layer from the surface of the liquid.

After that, the ultraviolet light laser creates the next layer, which selectively cures and solidifies the polymer liquid resin. The UV laser beam is focused using a set of mirrors to the predetermined path.

The mirrors are called galvos. The cross-section area is then scanned to ensure the parts that have been produced are solid.

After the first layer is done, the platform moves at a distance, and the sweeper blade coats the surface of the object. The process repeats itself until the whole model is done.

After printing, the object is green and not fully cured. At this point, the model requires more post-process, where it’s passed under the UV light. This is done in case high mechanical and thermal properties are needed.

Solidification occurs through the photopolymerization process. This happens when the UV laser activates the monomer carbon chain of liquid resin to become solid. After that, a strong bond that can’t be broken is created between each carbon.

After the photopolymerization, there is no way to reverse and convert the SLA part back to the liquid form. When you heat it, the object will only melt. This is because the materials produced are from thermoset polymer, unlike the thermoplastic materials used in the FDM processes.

Why Choose Stereolithography SLA 3D Printing?

There are several reasons why you should choose SLA 3D printing. The reasons are as follows.

1. Isotropy

The 3D printer prints a layer at a time. But there are differences in the strength of the different prints due to the parts’ orientation in the printing processes. In the SLA 3D printing process, resin 3D prints isotropic parts.

The printing process’s integration materials control a few factors. In printing technology, the materials form a covalent bond layer by layer to achieve isotropy parts. The 3D-printed parts formed remain in a semi-reactive state.

At that point, the materials still maintain the polymerizable group that helps to form bonds across the layers. This is what leads to isotropy and water tightness to the object once it is cured.

This is what makes part of SLA applicable in fixtures, jigs, and functional prototyping.

2. Watertightness

SLA printed parts are continuous, whether they are produced with solid features or using the internal channel. Water tightness is important, especially when designing an object where water and air need to be controlled.

Engineers have taken advantage of the water tightness of SLA’s printed parts and are using the technology to design automotive parts, objects used in biomedical research, and kitchen appliance parts.

3. Accuracy and Precision

With SLA’s technology and water tightness, one can come up with accurate and precise objects. This feature is what makes the SLA technology applicable in dental manufacturing. The accurate and precise parts are achieved as the SLA process is tightly controlled.

Compared to other processes, the SLA accuracy is standard. Also, SLA has the highest tolerance as compared to other technologies.

With the heated resin tank and closed build environment, almost identical parts are created. The better accuracy is due to the lower printing temperature because the SLA technology uses light in place of heat. The printing process happens at room temperature, which helps the printed part not to suffer from thermal expansion and contraction.

What Is an SLA 3D Printer?

It is an additive manufacturing process that uses a high-power UV laser that hardens liquid resins in the reservoir to create 3D objects.

Dental Crowns Printed in Laser Sintering Machine

In short, the photosensitive liquid is converted to a 3D object layer by layer using a low-power laser and photopolymerization.

SLA technology is one of the three major 3d printing technologies used in making highly detailed 3D parts without the need for much post-processing to come up with a high accuracy surface finish.

The other two technologies are FDM and selective laser sintering. Also, there is a process that uses the same technique as the SLA. The technology is known as digital light processing (DLP). The only difference is it uses a projector screen, unlike the SLA.

What Is the Difference Between DLP and SLA 3D Printing?

The major difference between SLA technology and the DLP is the source of light. SLA gets its light from the UV laser beam, while the DLP gets UV light from a projector.

Another difference is the UV light from the projector in the DLP process is stationary. Simultaneously, the UV laser beam from the SLA technology moves from one point to another, tracing the geometry of the object.

SLA technology is more accurate as compared to the DLP. This is due to the hardening of the materials from point to point. This feature makes the SLA better compared to the DLP.

The DLP technology is way faster than the SLA and helps to cut the printing time significantly.

While printing using DLP technology, you can control the intensity of the UV, which can control the effect of the materials. On the other hand, SLA can’t control the laser beam unless you change the whole laser beam to get a different effect.

The DLP UV light is less expensive, and so you can easily replace it, unlike the laser light, which is expensive.

If you are building a one-off small part, then the DLP is the best technology to use. SLA is best when you are creating several intricate parts.

If you are printing large parts with fewer details, DLP technology is best as it is quick. But if the object has intricate details, then SLA is best for the job.

Is SLA or FDM Better?

When you are faced with an SLA vs. FDM situation in deciding the better printer, you need to consider the following key aspects:

1. Print quality and precision

When you use additive manufacturing processes to create 3D prints, you must create each layer separately, which increases the chances of inaccuracy. If you compromise on precision, you are likely to end up with a poor-quality 3D model.

Stereolithography 3D systems create 3D prints by making layers of filament using a laser that assures high levels of precision. When it comes to making finished 3D models, you should expect a smooth surface from SLA 3D printing.

Here, the chances of compromising accuracy are less due to the use of high-precision lasers.

FDM 3D printing, on the other hand, creates objects by extruding molten material on the build plate in lines. The only way to achieve precision in this printing technology is to carefully select an extruder nozzle of a preferred size.

At times you will have void durations when extruding, which may affect adhesion. You will often see the layers of your 3D print, which is not the same case with stereolithography printing technology.

2. Engineering materials used

3D printing requires the use of engineering materials. For this reason, you have to choose the printing technology that supports the engineering materials you have or must use.

A few selected FDM 3D system printers use PETG, TPU, and nylon. You’ll also find some FDM printers that support the use of high-performance thermoplastics such as PEI or PEEK. If this is the 3D printing material you prefer using, then FDM 3D systems are better for you.

Users of SLA 3D systems, on the other hand, enjoy using a wide range of materials. These SLA 3D printers are versatile and function using almost every engineering material available, including those used by FDM 3D systems.

3. Build volume

When deciding which printing technology to go with between SLA machines and fused deposition modeling machines, ask yourself, what is my target build volume? If your build volume needs are large, FDM printers will serve you best.

This is because making large 3D prints using an FDM 3D printer is uncomplicated. The build volumes of FDM 3D systems are not as limited as those of SLA 3D systems because fused deposition modeling has a bigger build platform.

Stereolithography 3D systems, on the other hand, are more modern and are created in smaller designs. A stereolithography printer will fit comfortably on your desk; hence they are referred to as desktop SLA 3D printers.

Since they are small in size, creating large 3D prints in them is challenging. Their build volumes are limited because printing a large 3D part will require more support which SLA 3D printers cannot provide.

4. Printing speed

Printing speed is another important factor to consider when faced with SLA vs. FDM 3D systems. Please note that you can only compare the printing speeds with the same layer heights.

If you want to print the same layer heights, SLA 3D systems will work faster and create a smooth surface finish.

On the other hand, fused deposition modeling printers will require more time to achieve the same layer height and quality.

Are SLA Prints Strong?

SLA uses special photopolymer resin that hardens when exposed to UV light. The resins used in the manufacturing process are both epoxy- and acrylate-based; they are mostly used in desktop printers.

Many people assume SLA printed parts are fragile and suitable for making ornaments and prototyping but not the heavy functions, but that’s not the case. The strength of the printed objects depends on the material you use to print. When you use generic materials, then the parts will be weak and fragile.

There are strong resins used in manufacturing strong objects. There are resins for jewelry and those for manufacturing dentistry objects, crowns, and surgical guides.

There are also high-temperature resins used in developing parts that are exposed to high temperatures. Ensure you get the right materials for the job.

Stereolithography is used in producing plastic parts with high resolution, fine details, and are smooth and accurate. SLA technology has many applications, which include:

SLA printing technology has the following advantage as compared to other printing technologies.

They produce smooth injected models with a surface finish. It also produces objects with fine features, and great details are captured in the printed models. Also, the parts produced are stiff, making them more durable.


With the above information, it’s clear what SLA printing is. This information is important, especially if you are working with a 3D SLA printer. You need to know what to use and how to go about printing.

As seen above, ensure you have the right resin when printing to come up with strong, durable parts.

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.