SLA vs SLS comes down to one trade-off: detail versus durability. SLA (resin) gives you the smoothest surface and the finest detail; SLS (nylon powder) gives you the strongest, most functional parts. Almost every other difference — supports, cost, finish, materials — flows from that single distinction. Get clear on which one your part actually needs and the decision makes itself.
This guide breaks down how each process works, where each wins, and how to choose. When you're ready to order either, the 3D Prototyping Hub directory lists providers running both.
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How Each Process Works
SLA (Stereolithography) builds parts from liquid photopolymer resin. A light source — a laser in traditional SLA, an LCD screen in the desktop MSLA variant — cures the resin one thin layer at a time. Because the layers are optically defined, SLA captures extremely fine detail and produces a smooth surface. Parts need support structures during the build, and they require washing and UV curing after printing.
SLS (Selective Laser Sintering) builds parts from a bed of nylon powder. A laser scans each layer, fusing powder into solid material; the bed then drops, a fresh layer of powder is spread, and the process repeats. The unfused powder surrounding the part supports it during the build — which is why SLS needs no support structures at all. That single fact unlocks complex geometries, internal channels, and dense nesting of many parts in one build.
That difference in how the layer is formed — curing liquid vs. fusing powder — is the root of every practical difference below.
Surface Finish and Detail
SLA wins decisively. Resin parts are smooth off the plate and hold sharp edges, thin walls, fine text, and intricate features. This is why SLA is the go-to for presentation models, cosmetic prototypes, and master patterns.
SLS parts have a matte, slightly grainy, powdery finish and softer fine detail. It's a perfectly good functional finish, and it can be upgraded with tumbling, dyeing, or vapor smoothing — but out of the box, SLS looks like a functional part, not a finished product.
Mechanical Properties
SLS wins decisively. Sintered nylon (typically PA 12) is tough, impact-resistant, and near-isotropic — it behaves consistently regardless of build orientation, which matters for parts under real load. It handles snap fits, living hinges, and repeated use well, making it genuinely suitable for functional and end-use parts.
Standard SLA resin is comparatively brittle and can become more so with UV exposure over time. Tough, durable, and engineering resins close much of the gap for functional resin parts, but for load-bearing, impact-prone, or long-life parts, SLS is the more forgiving choice.
Supports, Geometry, and Design Freedom
SLS needs no supports, so complex organic shapes, enclosed voids, lattices, and consolidated assemblies print freely — and dozens of parts can be packed into a single powder bed. This is a real design and throughput advantage.
SLA needs supports on overhangs, which means support marks to clean up and some geometry constraints. It excels at small, detailed, relatively simple parts rather than complex functional assemblies.
Cost and Volume
For one or a few small parts, SLA — especially desktop MSLA — is usually the cheaper route. For batches of functional parts, SLS often wins: no supports plus dense nesting means the machine's higher cost gets spread across many parts efficiently, so per-part cost drops as quantity rises. This makes SLS a common choice for low-volume production runs. For how printed cost is built up in general, see How Much Does 3D Printing Cost?.
A Simple Decision Framework
- Cosmetic prototype, presentation model, fine detail, smooth surface → SLA
- Master pattern for casting, dental, jewelry, small sharp-featured parts → SLA
- Functional or end-use part, snap fits, living hinges, real mechanical load → SLS
- Complex geometry, internal channels, consolidated assemblies → SLS
- Small batch of durable parts (low-volume production) → SLS
- Needs both strength and a cosmetic finish → SLS with post-processing, or compare both quotes
When you're unsure, get a quote for the same geometry from an SLA-capable and an SLS-capable provider, and weigh finish, strength, and per-part cost against what the part actually has to do.
How This Compares to SLA vs FDM
If you were also weighing FDM, the mental model stacks up cleanly: FDM is the cheapest, fastest route for functional prototypes in engineering thermoplastics; SLA is the detail-and-finish specialist; SLS is the strength-and-production specialist that needs no supports. For the resin-versus-extrusion side of that comparison, see SLA vs. FDM Printing Explained. For a deeper look at the powder process on its own, see SLS 3D Printing Services.
Find a Provider for Either Process
Whether your part calls for SLA detail or SLS strength, browse the 3D Prototyping Hub directory, shortlist two or three providers that run the technology your part needs, and submit the same file to each for comparable quotes. Run a shop offering resin or powder-bed printing? Claim your listing to start receiving quote requests.
A note on going in-house: SLA has a real desktop path — Anycubic's MSLA machines paired with standard or ABS-like resin bring resin detail in-house affordably. SLS does not: it remains an industrial service-bureau process, so for nylon parts a provider is effectively your only route. If resin printers are on your radar, Best Resin 3D Printers in 2026 covers the current picks.
Related Resources
- SLA vs. FDM Printing Explained — resin versus extrusion
- SLS 3D Printing Services — the powder-bed nylon process in depth
- Functional and End-Use 3D Printed Parts — when parts have to perform
- Best Resin 3D Printers in 2026 — desktop SLA/MSLA options
- How Much Does 3D Printing Cost? — what drives the printed price
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