Stereolithography (SLA) 3D printing is the most common resin 3D printing process that has become vastly popular for its ability to produce high-accuracy, isotropic, and watertight prototypes and end-use parts in a range of advanced materials with fine features and smooth surface finish.
What is Stereolithography 3D Printing?
Stereolithography belongs to a family of additive manufacturing technologies known as vat photopolymerization, commonly known as resin 3D printing. These machines are all built around the same principle, using a light source—a laser or projector—to cure liquid resin into hardened plastic. The main physical differentiation lies in the arrangement of the core components, such as the light source, the build platform, and the resin tank.
SLA 3D printers use light-reactive thermoset materials called “resin.” When SLA resins are exposed to certain wavelengths of light, short molecular chains join together, polymerizing monomers and oligomers into solidified rigid or flexible geometries.
The SLA 3D Printing Workflow
- Use any CAD software or 3D scan data to design your model, and export it in a 3D printable file format (STL or OBJ). Each SLA printer includes software to specify printing settings and slice the digital model into layers for printing. Once setup is complete, the print preparation software sends the instructions to the printer via a wireless or cable connection.
- After a quick confirmation of the correct setup, the printing process begins and the machine can run unattended until the print is complete. In printers with a cartridge system, the material is automatically refilled by the machine.
- Once the printing is completed, parts require rinsing in isopropyl alcohol (IPA) to remove any uncured resin from their surface. After rinsed parts dry, some materials require post-curing, a process which helps parts to reach their highest possible strength and stability. Finally, remove supports from the parts and sand the remaining support marks for a clean finish. SLA parts can be easily machined, primed, painted, and assembled for specific applications or finishes.
A Brief History of Stereolithography
The SLA 3D printing process first appeared in the early 1970s, when Japanese researcher Dr. Hideo Kodama invented the modern layered approach to stereolithography, using ultraviolet light to cure photosensitive polymers. The term stereolithography was coined by Charles (Chuck) W. Hull, who patented the technology in 1986 and founded the company 3D Systems to commercialize it. Hull described the method as creating 3D objects by successively “printing” thin layers of a material curable by ultraviolet light.
SLA 3D printing, however, was not the first 3D printing technology to gain widespread popularity. As patents began to expire at the end of the 2000s, the introduction of small format, desktop 3D printing widened access to additive manufacturing, with fused deposition modeling (FDM) first gaining adoption in desktop platforms.
While this affordable extrusion-based technology sparked the first wave of wide adoption and awareness of 3D printing, FDM 3D printers did not satisfy the spectrum of professional needs—repeatable, high-precision results are crucial for professional applications, as are biocompatible materials in the dental industry and the ability to create fine features for industries like jewelry and applications like millifluidics.