Stereolithography (SLA) 3D Printing: Everything You Need To Know

    3D PrintersStereolithography (SLA) 3D Printing: Everything You Need To Know


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    Stereolithography is a type of 3D printing that employs a computer-controlled moving laser beam, which is coordinated by CAM/CAD software.

    Stereolithography (SL) is an industrial 3D printing process used to create concept models, cosmetic – rapid prototypes, and complex parts with intricate geometries in as fast as 1 day.

    It’s the most common resin 3D printing process- check out the best resin 3D printers.

    SLA vs SL

    SLA is the abbreviation for Stereolithography Apparatus. SL is a generic’ abbreviation for stereolithography as a process, distinct from any particular type of equipment (Source).

    This process has a special place in the history of additive manufacturing as the very first and the best process to be developed in this industry, therefore, laying the ground for the development of other additive manufacturing processes.

    This process has been successfully applied in creating prototypes in sections such as computer hardware medical models; even though this process is faster and can produce typically any form of prototype, it’s costly.

    How it works

    The stereolithography uses a vat of liquid photopolymers resin that can easily be cured.

    The process begins with positioning the build platform in a tank of liquid photopolymer.

    The build plate of the model moves in small increments, thus letting the liquid polymer be exposed to light.

    As the photopolymer starts to solidify, a computer-controlled UV laser is directed, thus activating the monomer carbon chains that compose the liquid to create a solid with unbreakable solid bonds between them.

    Using a set of mirrors, a laser beam is then focused on the resin to draw layer by layer sections, after which the machine lowers the platform to somewhere between 0.002″ and 0.006″ to allow the fresh resin to be applied.

    The process continues with the UV laser adhering to each additional layer until the model is complete. The object is then pulled out of the resin, thus creating space for the uncured liquid resin, which is at the bottom of the container, to move to the next layer of the object.

    Characteristics of stereolithography printing

    i. Materials

    The materials used in the SLA printing process include clear resin, castable resin, and tough or durable resin.

    Clear resin is used because of its transparent properties and post-processing. Castable resin is also used to create mold patterns. It tends to have a low ash percentage after burnout, and lastly, resin-based on its ABS-like mechanical properties and low thermal resistance. Learn about resin toxicity issues here.

    ii. Dimensional accuracy

    The SLA printing is very versatile precise and produces smooth surfaces, making it ideal for dental implants and jewelry making. Nevertheless, the only drawback to this printing process is that it tends to deteriorate when it’s regularly exposed to sunlight due to its photosynthetic nature.

    iii. Typical layer buildup

    It includes the layer height and the buildup size. The layer height ranges between 25 to 100 microns.

    The lower crown is meant to capture the curved geometries accurately, but it’s critical to note that it increases the cost buildup time, thus increasing the probability of a failed print. Therefore a height of 100 microns is recommended.

    On the other hand, the buildup size is depended on the type of the SLA machine setups, with typically there being only two types of SLA machine setups, bottom-up and top-down printers.

    iv. Support structures

    They are usually required in SLA to ensure that the overhung has something to hold on to. They are printed with similar material as the part and should be manually removed after printing.

    The printed parts are the determinants of the amount and location of these support structures. It’s highly recommendable that the part is oriented to ensure that the visually critical surfaces of the model don’t come in contact with the support structure.


    This printing process has several advantages to its users. Some of those include:

    1. It can rapidly prototype, thus developing your whole final product in no time.

    2. The products of this process have a very smooth surface finish which comes in handy, especially when you need a realistic prototype with high quality and detailed features.

    3. It can aid in low-cost prototyping by potentially detecting costly mistakes and design flaws before the manufacturing process even start. Thus making it the best option for manufacturing low volume production parts.

    4. Its initial design has been refined over the years to model it into a multi-material production process. This means that potentially any model form, be it high temperature or highly abrasive applications, can be formed without necessarily deploying expensive machine techniques.


    1. The resin parts printed using this process are generally brittle thus not suitable for functional prototypes.

    2. The handling of photosensitive resin is a problem since it can start to form before it has even been applied to the model. This means that molding has to be carried out in darkened areas, including covered sections, to prevent the resin from being affected.

    3. It’s very costly; hence, the new cheaper 3D modeling processes producing similar quality and output levels have been preferred over it. Learn more about how much 3D printers cost.

    4. The visual accuracy and mechanical properties of the SLA parts will degrade over time, especially when exposed to direct sunlight.

    5. The visual marks left on the SLA parts require post-processing to be removed.

    The Types Of 3D Printing

    1. Stereolithography (SLA) 
    2. Selective Laser Sintering (SLS): (check out the best SLS 3D printers)
    3. Digital Light Processing (DLP)
    4. PolyJet 3D printing
    5. Multi Jet Fusion (MJF)
    6. Electron Beam Melting (EBM)
    7. Direct Metal Laser Sintering (DMLS)
    8. Binder Jetting (BJ) Technology
    9. Drop on Demand (DOD)
    10. Fused Deposition Modelling (FDM)

    Summing Up

    Stereolithography, also known as optical fabrication or stereolithography apparatus, refers to a form of 3D printing technology whose function is to create models, prototypes, and production parts layer by layer, which involves photochemical processes in which light causes chemical oligomers and monomers to cross-link into forming polymers.

    These polymers formed are then used to make the body of a three-dimensional solid.

    Rush Chapman
    ( Founder )

    Hello, my name’s Rush Chapman. I’m a 3D printing enthusiast. I started this site to help people choose 3D printing projects and select the best 3D printer for your needs, whether you’re a hobbyist or a pro!