What is Stereolithography (SLA)?
What is Stereolithography (SLA)?
Stereolithography (SLA) is one of several methods used to create 3D printed objects. It works by curing layers of a photopolymer (a light-sensitive liquid plastic) to create a part or object. The precise layering is guided by a CAD file that has been converted to an STL file, which digitally slices a 3D model of an object into layers. Each layer of photopolymer is exposed to a UV (ultraviolet) laser that immediately cures, or hardens it. Subsequent layers are cured and bonded to the previous layer until a complete three-dimensional object has been formed. That object is then cleaned and can be baked in a UV kiln to further cure the photopolymer.
SLA produces prototypes and small, precise objects faster than typical machining. This makes stereolithography printing ideal for detailed parts including jewelry, dental models, medical models and implants, and other things that would be expensive to machine otherwise.
SLA Printing Advantages and Disadvantages
SLA printers are popular for their ability to produce intricate objects and parts with a high degree of accuracy. Printers using this process are relatively affordable, so are often found in offices.
SLA printing produces strong odors due to curing photopolymers in the printing process, and the risk of warping in larger items. It’s generally best for smaller parts, and most parts are not particularly strong.
History of SLA Printing
In 1981, a functional rapid-prototyping system using photopolymers was invented by Hideo Kodama, which made a solid, printed model from many layers, each of which corresponded to a sectional slice in the model. Three years later, in 1984, Charles Hull invented the solid imaging process known as stereolithography —one of the earliest and most widely used forms of 3D printing — along with the STL file format that is necessary for translating CAD files for 3D printers.
FAQ
What is the difference between FDM printing vs SLA printing?
FDM (fused deposition modeling) and SLA (stereolithography) are both methods of 3D printing. Both print objects layer by layer. SLA uses a curable photopolymer that is hardened by applying a UV light. SLA printers typically build a three-dimensional object from top to bottom. The build platform lifts the object upwards out of the resin bath. FDM printers use thermoplastic, which is heated to its melting point and then extruded in layers to create a three-dimensional object.
How thick are the layers created by SLA? The photopolymer is applied in thin layers, usually between 0.025-0.3 mm.
What is a photopolymer? Also known as a resin, a photopolymer is an acrylic-based, liquid plastic material that instantly turns into a solid part when exposed to UV light.
Why use an ultraviolet laser? Lasers are fast and precise, so they can produce highly accurate models and prototypes. An ultraviolet (UV) laser reacts with photopolymers immediately to cure and harden them, accelerating the production process.
What kind of post processing is needed with SLA printing? Parts need to be rinsed in isopropyl alcohol to remove any uncured resin. Parts may need additional curing to increase strength from their surface, and sanding is often required to attain a desired surface.
What is an STL file? CAD files show a rendering of a 3D object; STL (Standard Tessellation Language) acts as a translator that digitally slices that image into layers, creating a file that can then be used to direct 3D printing machines in creating the object.