The Complete Guide to Stereolithography (SLA) in 3D Printing

Stereolithography (SLA) is a 3D printing process that uses an ultraviolet (UV) laser to cure and harden liquid photopolymer resin, building objects one thin layer at a time. It belongs to the family of technologies known as vat photopolymerization, and is commonly referred to as resin 3D printing. Valued for its fine detail and smooth surface finish, SLA is widely used for prototyping and for producing casting patterns.

Stereolithography is one of the earliest 3D printing methods. The technology was patented in 1984 by Charles “Chuck” Hull, and the first commercial machine was developed by 3D Systems in 1988. Decades later, the technology remains a major force in the industry. The global stereolithography 3D printing market was estimated at USD 2.91 billion in 2025 and is expected to reach USD 21.98 billion by 2035, according to Spherical Insights.

But how does it work? Find out below in our complete guide to stereolithography. For hardware recommendations, see our Top 10 resin 3D printers.

How Stereolithography 3D Printing Works

Like all 3D printing technologies, stereolithography starts from a digital file and builds the object one layer at a time. The vast majority of SLA printers today, including virtually every desktop and prosumer machine, use a bottom-up (inverted) configuration, so that’s the process described below:

1. File Preparation: The process begins with a 3D digital model, created in CAD software. The file (usually an STL) is imported into a slicer, which divides the model into thin horizontal layers and generates the instructions sent to the 3D printer.
2. The Machine Setup: A typical SLA printer contains a resin tank with a transparent, non-stick film (usually FEP) at its base, a build platform that moves along the Z axis, a UV laser, focusing optics, and a galvanometer-driven mirror system that steers the laser beam across the X and Y axes. The build platform starts lowered into the tank, positioned just above the film.
3. Layer Curing: Guided by the sliced model, the UV laser sweeps across the resin through the transparent base of the tank, selectively curing and solidifying it against the build platform. This traces out the geometry of a single layer from the bottom up.
4. Peel and Lift: Once a layer is cured, the platform lifts slightly to separate the new layer from the film, a step known as the peel. The platform then drops back down by one layer thickness so the next cross-section can be cured beneath the last. This cycle repeats, layer by layer, with the part gradually rising out of the tank until it is complete.

The main exception is large-format and industrial stereolithography, where machines instead cure from the top down. Here the build platform starts at the top of a deep, fully filled resin tank and descends one layer at a time, with the laser curing each new layer on the open surface of the resin. Because there is no film to peel away from, this approach avoids the separation forces that stress delicate features, which is why it remains the standard for very large parts.

Post-Processing in Stereolithography

Unlike some 3D printing technologies, an SLA part is not finished when it leaves the printer. It comes out coated in sticky, uncured resin and has not yet reached its full mechanical strength, so post-processing is a mandatory part of the workflow. There are typically three steps:

1. Washing: The part is rinsed in a solvent, usually isopropyl alcohol (IPA, also called isopropanol), to remove the excess liquid resin clinging to its surface. Many workflows use a dedicated wash station that agitates the part in solvent for a set time. Some newer resins are water-washable, allowing this step to be done with water instead.
2. Support Removal: Like FDM, SLA relies on support structures to hold up overhangs and features that would otherwise sag or float during printing. These supports are removed after washing, either by hand or with cutters, leaving small contact marks that can be sanded smooth.
3. UV Curing: The washed part is exposed to additional UV light, often in a dedicated curing chamber, to complete the photopolymerization reaction. This final cure hardens the resin fully and maximizes the strength of the finished part.

Once cured, SLA parts can be sanded, primed, and painted like most plastics. Stereolithography is prized for its surface quality: the finish is smooth and slightly glossy, and for a given layer thickness it is generally superior to what FDM or SLS can achieve, with individual print layers often barely visible.

The Different Types of Resin 3D Printing

Stereolithography is the original vat photopolymerization technology, but not the only one. After the early SLA patents expired, manufacturers developed other ways to cure liquid resin, differing mainly in their light source and how much of each layer they expose at once. This affects speed, resolution, and cost.

• SLA (laser): A single UV laser traces each layer point by point. The original method, prized for accuracy and surface finish, but comparatively slow. Used by professional systems from the likes of 3D Systems and Formlabs.
• DLP (Digital Light Processing): A digital projector flashes a whole layer at once, making it faster than laser SLA. Resolution is tied to projector pixel size. France’s Prodways developed a moving-projector variant called MovingLight.
• MSLA / LCD (Masked SLA): An LCD screen masks a UV LED array to expose a full layer at once. Cheap and fast, it now powers the vast majority of affordable desktop printers (Elegoo, Anycubic, Phrozen). Detail depends on screen resolution, hence the race toward 4K, 8K, and beyond.
• CLIP / CDLP (continuous): Carbon’s continuous approach uses an oxygen-permeable window to draw parts upward without pausing to peel between layers, printing dramatically faster and yielding strong, isotropic parts suited to production.

Resin 3D Printing Materials

 Unlike FDM’s solid thermoplastics, resins are formulated for specific properties, and choosing the right one matters more than almost any other decision in resin printing. The main categories are:

• Standard resins: The default for visual prototypes and highly detailed models. They deliver excellent surface finish and fine features but are relatively brittle, so they suit display parts rather than functional ones.
• Tough and engineering resins: Formulated to mimic engineering plastics like ABS or polypropylene, with greater strength and impact resistance for functional prototypes, housings, and snap-fit parts.
• Castable resins: Designed to burn out cleanly with little to no ash, making them ideal for lost-wax casting in jewelry and dentistry, where a printed pattern is used to produce a metal part.
• Flexible and elastic resins: Rubber-like materials used for gaskets, grips, wearables, and other parts that need to bend or compress.
• Dental and medical resins: Biocompatible, often certified materials used for aligners, surgical guides, crowns, dentures, and models. This is one of the largest professional markets for resin printing today.
• High-temperature resins: Heat-resistant formulations for demanding applications such as molds, tooling, and parts that must withstand elevated temperatures during testing.
• Ceramic resins: Photopolymers heavily loaded with ceramic particles such as alumina, zirconia, or silica. The printer produces a fragile “green” part in which the cured resin only acts as a binder; it must then be debinded and sintered in a furnace to burn off the polymer and fuse the ceramic into a dense, solid part. This makes ceramic printing a mainly industrial process, used for dental restorations, medical implants, and aerospace and electronics components.

A general trade-off runs through all of these: resins that capture the finest detail tend to be more brittle, while tougher, more durable resins often sacrifice some resolution. Resin is also a consumable with a shelf life, and it must be handled with gloves and stored away from light before curing. For a deeper look into these materials, check out our resin guide.

How Much Does a Resin 3D Printer Cost?

Resin 3D printers span a wide range depending on their light source and build size. Entry-level MSLA desktop machines, which dominate the consumer market, start at roughly $200 to $300, while enthusiast and prosumer models with larger build volumes and more automation typically run $400 to $800. Professional SLA systems, such as those from Formlabs, generally fall between $2,000 and $10,000 (the Form 4 starts around $3,500), and large-format or industrial machines range from about $5,000 to $25,000 and beyond. On top of the hardware, resin is an ongoing consumable, usually costing $30 to $80 per liter (more for specialty dental, castable, or engineering formulations), and buyers should also budget for isopropyl alcohol, replacement FEP film, and post-curing equipment.

Frequently Asked Questions about Stereolithography