SLA 3D printing

SLA 3D printing (stereolithography) is one of the oldest and most accurate 3D printing technologies. A photopolymer resin is cured layer by layer with a UV laser, or alternatively with a projector or an LCD mask (the DLP and MSLA variants).

The main advantages of SLA printing are high accuracy (roughly ±0.025 to 0.1 mm on smaller parts) and surface quality. Prints are smoother than FDM prints and capture fine details. That is why SLA is used for visual models, dental applications, jewelry, small precision mechanical parts and prototypes where appearance matters.

SLA materials are resins with a range of properties: standard, clear, rigid, tough, flexible, high-temperature or biocompatible. The drawbacks are the higher material cost compared with FDM, the post-processing that is always required (washing in isopropyl alcohol and post-curing under UV light) and sensitivity to UV radiation when parts are used outdoors.

DLP (digital light processing) is a related technology in which a projector cures an entire layer at once instead of a laser tracing it point by point. The result is faster printing at comparable quality.

Choose SLA printing when detail, a smooth surface or accuracy on small parts matters: visual and presentation models, prototypes of consumer electronics housings, small mechanisms, connectors, parts with fine text or texture, and master patterns for silicone molds and vacuum casting (in the US often called urethane casting).

Clear resins are useful for visualizing flow in channels or for light pipes, and specialty resins for testing at elevated temperatures or for dental and medical applications.

Standard resins are brittle, and over time, especially in sunlight, they become even more brittle and change color. For functional parts, snap fits and screw connections, ask for a tough or engineering resin, or consider SLS instead. Mechanical properties vary from one resin manufacturer to another, so do not rely on generic values.

Large and thin-walled parts can warp, supports leave marks that have to be sanded off, and hollow parts need drain holes for uncured resin. Check with your supplier which resin they will use, whether they fully post-cure the part and where the support marks will be.