Stereolithography: 3D Printing by Laser solidyfing Liquid-Resin

Among all 3D printing technologies, Stereolithography (or SLA) might be one of the oldest techniques ever developed. Stereolithography is an additive manufacturing technique using resin. What is this additive manufacturing technique, where does it come from and what are the advantages? Here is a complete introduction to SLA 3D printing.

What is Stereolithography?

When taking a look at the history of 3D printing SLA appears to be the first concept of 3D printing ever developed. During the ’80s a French team of engineers Olivier de Witte, Jean-Claude André, and Alain Le Méhauté, was interested in the stereolithography technology but unfortunately, they abandoned their project due to a lack of business perspective. At the same time, Charles Hull was also interested in the technology and submitted the first patent for stereolithography (SLA) in 1986. Charles Hull then founded the 3D Systems Corporation and in 1988, the company released its first product, the SLA-1 3D printer.

Stereolithography (SLA) is a resin 3D printing or additive manufacturing process using photochemical processes. This SLA 3D printing process uses a vat of liquid photopolymers resin that can be cured. The build plate moves down in small increments and the liquid polymer is exposed to light where the UV laser draws a cross-section layer by layer. The process repeats until a model has been created. The object is 3D printed by pulling the object out of the resin (bottom-up) which creates space for the uncured resin at the bottom of the container and can then form the next layer of the object. Another way is to 3D print the object by pulling it down into the tank with the next layer being cured on the top.

What are the characteristics of SLA?

There are different ways to print SLA, as we just saw, the main difference is their orientation. It can be a bottom-up process or a top-down process, depending on the 3D printer. Indeed, desktop 3D printers are using the bottom-up technique, like Formlabs 3D printers, while the top-down ones are more industrial 3D printers. Desktop SLA printers are cheaper and easier to operate, while industrial 3D printers allow building really large-size objects but need a specialized technician to be operated. Moreover, these 3D machines are really fast.

Another thing with SLA 3D printing is that you need a support structure to print your resin part. Once again, these supports are easier to develop for desktop 3D printers as it is quite similar to Fused Deposition Modeling (FDM) supports. These are needed to print correctly any overhangs and bridges. You can choose the orientation of the part, choosing which orientation actually requires less support structure. For industrial SLA machines, a support structure is still needed, but you can’t plan on choosing the orientation. All these supports have to be removed manually from the 3D printed part.

Post-process is also part of the manufacturing process with Stereolithography. At the end of the process, the part is removed from the platform, the excess of resin also has to be removed from the part. Then, the resin part will go through a curing process, in a UV oven, which will help the final part to reach its final stability.

How is Stereolithography used?

Stereolithography 3D printing is actually well-used for medical applications, to create accurate 3D models as a great help to plan surgeries. This technique is more and more common, helping surgeons to save time and be even more prepared in order to deliver the best treatment possible to their patients.

This technology is also particularly used in the dental industry to create detailed components. But just like all 3D printing technologies, this 3D printing technique can be used in various sectors, such as engineering, fashion, automotive, consumer product or education.

Advantages and disadvantages of Stereolithography

Stereolithography offers a lot of advantages, it can help you rapidly prototype, or develop your whole final product.

These photopolymer parts do not have the strength of Selective Laser Sintering (SLS) or FDM 3D printed parts, but can typically achieve much higher levels of detail and great complex geometries. As the photopolymer is UV sensitive, these products are susceptible to deforming and changing colors in sunlight. SLA is commonly used to generate highly detailed artwork, non-functional prototypes, and can be used to make molds in investment casting applications.

SLA parts have a really smooth surface finish, which is particularly adapted if you need a realistic prototype with high quality and detailed features, quite similar to injection molding parts. But resin parts printed with Stereolithography are not suitable for functional prototypes.

What about SLA materials?

Regarding the 3D printing materials compatible with this technology, it is possible to use various types of resins, it will depend on on the SLA 3D printer you want to use and the needs of your 3D printing project.

Check out here a few examples of professional SLA 3D printers:

3D Systems iPro 8000

EnvisionTEC Perfactory 4 DSP

EnvisionTEC ULTRA 3SP

EnvisionTEC Xtreme 3SP