Stereolithography (SLA) 3D printing stands as a pioneering technology in the realm of additive manufacturing, renowned for its precision and ability to create intricate and high-resolution parts. At its core, a Stereolithography 3d Printer harnesses the power of light to transform liquid resin into solid three-dimensional objects, layer by layer. This process, known as photopolymerization, is the fundamental principle behind how SLA 3D printers operate.
Traditional SLA 3D printing systems, in their original design, positioned the light source, typically a UV laser, above a vat of liquid resin. This top-down approach involved the laser selectively curing each layer from the top surface of the resin. However, a significant advancement in SLA technology emerged with the introduction of inverted stereolithography in 2011. Pioneered by Formlabs’ co-founders, inverted SLA revolutionized the process by placing the light source beneath the resin vat.
Inverted stereolithography operates by projecting the light pattern from below, tracing the cross-section of each layer onto the bottom-most layer of resin. As each layer is cured, the build platform incrementally rises, allowing fresh liquid resin to flow beneath the newly solidified layer. This innovation was crucial in enabling the creation of larger and more efficient stereolithography 3D printers.
Several key technological breakthroughs paved the way for inverted stereolithography. One of the most significant was the development of transparent and eventually flexible bottomed resin tanks. This novel tank design played a critical role in mitigating peel forces, which are the forces exerted when separating the cured layer from the bottom of the tank. By utilizing a flexible surface at the bottom of the resin tank, inverted SLA 3D printers could achieve larger build volumes and improved print reliability.
SLA 3D printers utilize a specific type of material known as resin, which is a light-reactive thermoset polymer. These specialized resins are engineered to undergo photopolymerization when exposed to specific wavelengths of light. During the SLA printing process, the light source precisely targets the liquid resin, causing short molecular chains within the resin to crosslink and solidify. This process transforms monomers and oligomers into rigid or flexible three-dimensional structures, depending on the formulation of the resin.
Over the past decade, the landscape of resin 3D printing has expanded significantly, giving rise to various subtypes of stereolithography. These advanced techniques are primarily distinguished by the type of light source employed to cure the resin. Common variations include laser-based stereolithography (SLA), Digital Light Processing (DLP), and Masked Stereolithography (MSLA), also frequently referred to as LCD 3D printing. Each of these methods offers unique advantages in terms of speed, precision, and cost-effectiveness, catering to diverse application requirements.
An illustrative representation of Formlabs’ Low Force Display™ (LFD) print engine, a sophisticated iteration of MSLA 3D printing technology.
Regardless of the specific type of light source or its orientation (top-down or inverted), the fundamental workflow of stereolithography 3D printing remains consistent. After the 3D printer completes the part fabrication, a crucial post-processing step involves washing the printed part with alcohol or ether. This washing stage effectively removes any uncured liquid resin remaining on the surface of the part, ensuring a clean and accurate final product. Furthermore, depending on the specific resin material used and the desired mechanical properties, a post-curing step may be necessary. Post-curing typically involves exposing the printed part to UV light within a dedicated curing chamber, which further completes the polymerization process and optimizes the material properties of the 3D printed object.
Beyond washing and post-curing, additional post-processing methods can be employed to enhance the functionality and aesthetics of SLA 3D printed parts. These advanced finishing techniques include coloring, coating, or plating, which can be tailored to meet specific application requirements or achieve desired visual appearances. These post-processing options expand the versatility of stereolithography 3D printing, making it suitable for a wide array of industries and applications, from rapid prototyping and product development to creating end-use parts with exceptional detail and surface finish.
