Stereolithography (SLA)

Stereolithography (SLA) 3D prints highly detailed plastic parts by laser-curing liquid resin, delivering smooth surfaces and fine features with moderate strength and UV sensitivity.

Overview

Stereolithography (SLA) is a resin-based 3D printing process that uses a UV laser to cure liquid photopolymer layer-by-layer. It excels at fine detail, sharp edges, thin walls, and cosmetic surface finish with minimal visible layer lines—often the best choice for “looks-like” prototypes and master patterns.

Choose SLA for low-quantity parts where accuracy and surface quality matter more than toughness: form/fit prototypes, housings, fluidic features, and molds or casting patterns. Expect post-processing (washing and UV cure) and support removal, which can affect delicate features.

Tradeoffs: photopolymer resins are generally more brittle than engineering thermoplastics, with property drift under UV/heat and lower impact/fatigue performance. Large flat parts can warp, and internal cavities need drain/vent paths to avoid trapped resin. Cost scales with part volume and support complexity more than with simple footprint.

Common Materials

  • Standard resin
  • Tough resin
  • High-temp resin
  • Flexible resin
  • Clear resin
  • Castable resin

Tolerances

±0.003 in (±0.08 mm)

Applications

  • Form/fit enclosures and housings
  • Dental models and surgical guides
  • Clear fluidic manifolds and flow-visualization parts
  • Casting patterns for investment casting
  • Master patterns for silicone urethane casting
  • Small threaded or snap-fit prototype features

When to Choose Stereolithography (SLA)

SLA fits low-volume prototypes and bridge builds where crisp detail, smooth surfaces, and dimensional control are the main requirements. It works well for small-to-medium parts with thin features, cosmetic needs, or patterns for molding/casting. Plan on post-processing and design features that tolerate support contact and resin drainage.

vs Fused Deposition Modeling (FDM)

Choose SLA when you need sharper detail, smoother surfaces, and tighter control on small features than typical FDM can deliver. SLA is better for cosmetic prototypes and fine geometry; it’s less forgiving for rugged functional parts and high-temperature environments.

vs Selective Laser Sintering (SLS)

Choose SLA when surface finish, fine edges, and small features are more important than toughness. SLA parts typically look better out of the machine, while SLS usually wins for durable nylon parts and complex assemblies without supports.

vs Multi Jet Fusion (MJF)

Choose SLA for high-resolution features, thin walls, and presentation-quality surfaces, especially on smaller parts. MJF is usually better when you need stronger, more consistent thermoplastic performance and batch production of many parts.

vs Digital Light Processing (DLP)

Choose SLA when you need strong feature fidelity across varied geometries and can benefit from a scanned laser’s controllable exposure. DLP can be faster for trays of small parts, but SLA often holds detail well on mixed part sizes without pixel artifacts showing on surfaces.

vs PolyJet

Choose SLA when you want crisp detail and good surfaces at a lower material/process cost and can live with single-material resin behavior. PolyJet is better for multi-material, overmold-like prototypes, and very smooth surfaces, but it comes with higher cost and wax/support considerations.

Design Considerations

  • Add drain and vent holes for hollow sections to prevent trapped resin and post-cure blowouts
  • Avoid large, thin flat panels; add ribs or curvature to reduce warping during print and post-cure
  • Orient cosmetic surfaces away from supports and define no-support / no-touch faces on drawings
  • Use consistent wall thickness and avoid knife edges; keep minimum walls realistic for the selected resin and part size
  • Oversize and then ream/reamer-ready critical holes; expect small holes to print undersize and require cleanup
  • Call out finishing expectations (as-printed, sanded, painted, clear-coated) since post-processing drives cost and lead time