Why Choose SLA 3D Printing?

Engineers, designers, manufacturers, and more choose SLA 3D printing for its fine features, smooth surface finish, ultimate part precision and accuracy, and mechanical attributes like isotropy, watertightness, and material versatility.

Isotropy

Because 3D printing creates parts one layer at a time, completed prints may have variations in strength based on orientation of the part relative to the printing process, with different properties in X, Y, and Z axes.

Extrusion-based 3D printing processes like fused deposition modeling (FDM) are known for being anisotropic due to layer-to-layer differences created by the print process. This anisotropy limits the usefulness of FDM for certain applications, or requires more adjustments on the part geometry side to compensate for it.

Read our in-depth guide about FDM vs. SLA 3D printers to learn how they compare in terms of print quality, materials, applications, workflow, speed, costs, and more.

In contrast, SLA resin 3D printers create highly isotropic parts. Achieving part isotropy is based on a number of factors that can be tightly controlled by integrating material chemistry with the print process. During printing, resin components form covalent bonds, but layer to layer, the part remains in a semi-reacted “green state.”

While in the green state, the resin retains polymerizable groups that can form bonds across layers, imparting isotropy and watertightness to the part upon final cure. On the molecular level, there is no difference between X, Y, or Z planes. This results in parts with predictable mechanical performance critical for applications like jigs and fixtures, end-use parts, and functional prototyping.

SLA printed parts are highly isotropic compared to those produced with fused deposition modeling (FDM).

Because they are isotropic, SLA printed parts like this jig from Pankl Racing Systems can withstand the variety of directional forces they undergo during high stress manufacturing operations.

Watertightness

SLA printed objects are continuous, whether producing geometries with solid features or internal channels. This watertightness is important for engineering and manufacturing applications where air or fluid flow must be controlled and predictable. Engineers and designers use the watertightness of SLA printers to solve air and fluid flow challenges for automotive uses, biomedical research, and to validate part designs for consumer products like kitchen appliances.

OXO relies on the watertightness of SLA printing to create robust functional prototypes for products with air or fluid flow, like this coffee maker.

Accuracy and Precision

Industries from dental to manufacturing depend on SLA 3D printing to repeatedly create accurate, precise components. For a print process to produce accurate and precise parts, multiple factors must be tightly controlled.

Compared to machined accuracy, SLA 3D printing is somewhere between standard machining and fine machining. SLA has the highest tolerance of commercially available 3D printing technologies. Learn more about understanding tolerance, accuracy, and precision in 3D printing.

The combination of the heated resin tank and the closed build environment provides almost identical conditions for each print. Better accuracy is also a function of lower printing temperature compared to thermoplastic-based technologies that melt the raw material. Because stereolithography uses light instead of heat, the printing process takes place at close to room temperature, and printed parts don't suffer from thermal expansion and contraction artifacts.

Low Force Stereolithography (LFS) 3D printing houses the optics inside a Light Processing Unit (LPU) that moves in the X direction. One galvanometer positions the laser beam in the Y direction, then directs it along across a fold mirror and parabolic mirror to deliver a beam that is always perpendicular to the build plane, so it is always moving in a straight line to provide even greater precision and accuracy, and allows for uniformity as hardware scales up to larger sizes, like Formlabs larger format SLA printer Form 3L. The LPU also uses a spatial filter to create a crisp, clean laser spot for greater precision.

The characteristics of individual materials are also important for ensuring a reliable, repeatable print process.

Formlabs Rigid Resin has a high green modulus, or modulus before post-curing, which means it’s possible to print very thin parts with precision and a lower chance of failure.