What Is Stereolithography?

Stereolithography is an additive manufacturing process that builds three-dimensional objects by selectively curing liquid photopolymer resin with an ultraviolet light source, hardening it layer by layer into a solid structure. Developed in the 1980s and patented by Charles Hull in 1986, it was the first commercially viable 3D printing technology and remains one of the most precise methods for producing complex polymer parts. The process falls under the broader category of vat photopolymerization, in which a photosensitive liquid is progressively solidified from a reservoir.

The technique draws on photochemistry, optics, and materials science. During curing, UV light activates monomer chains within the liquid resin, triggering crosslinking reactions that transform the material from a flowable liquid to a solid polymer network. The spatial resolution of the cured layer is governed by the spot size of the UV source and the optical properties of the resin.

Process Mechanics

In a classic stereolithography system, a UV laser traces each cross-sectional layer of a computer model across the surface of the resin vat. After each layer cures, the build platform descends by one layer thickness, exposing fresh resin for the next pass. In inverted systems, widely used in desktop printers, the light source sits below a transparent-bottomed vat and the platform rises upward, peeling each cured layer from the bottom surface before the next exposure begins.

Layer thicknesses typically range from 25 to 300 micrometers, contributing to the smooth surface finish that distinguishes stereolithography from extrusion-based printing methods. The Formlabs guide to stereolithography documents how modern inverted systems use collimated LED arrays rather than scanning lasers, increasing throughput without sacrificing resolution. Post-processing generally involves rinsing parts in isopropyl alcohol and exposing them to a UV flood cure to complete polymerization.

Laser Sintering and Related Processes

Laser sintering, another light-driven additive process, uses a high-power laser to fuse powdered materials such as nylon or metal rather than curing a liquid. While both techniques use lasers and build objects layer by layer, stereolithography operates on photopolymerization chemistry while sintering relies on thermal bonding. The distinction matters for material selection: stereolithography is confined to UV-curable resins, whereas sintering opens access to a much wider palette of engineering polymers and metal powders. Research published in Communications Materials has explored high-resolution variations of stereolithography that use constrained liquid interfaces to improve Z-axis fidelity and reduce the peel forces that limit layer speed in inverted systems.

Resin Materials and Performance

The mechanical properties of a stereolithography part depend almost entirely on the resin formulation. Standard resins produce stiff, somewhat brittle parts suitable for visual prototypes and design verification. Engineering-grade resins offer higher impact resistance, flexibility, or thermal stability, with heat-deflection temperatures reaching above 200 degrees Celsius for specialized high-temperature formulations. Biocompatible resins meeting ISO 10993 standards are used to fabricate surgical guides, dental models, and audiological devices. Castable resins burn out cleanly at jewelry and investment casting temperatures. Recent advances in silicone and ceramic resin formulations have expanded the process into previously inaccessible material families, as reviewed in a ScienceDirect survey of stereolithography-based additive manufacturing applications and challenges.

Applications

Stereolithography has applications across a wide range of engineering and scientific domains, including:

• Rapid prototyping of mechanical and consumer product designs
• Dental and orthodontic model fabrication for crown, bridge, and aligner workflows
• Surgical planning models and custom implant templates in medical settings
• Aerospace wind tunnel test components and low-volume tooling
• Jewelry casting patterns using burnout-compatible resins
• Microfluidic device fabrication in laboratory and biomedical research