What is SLA (Resin) Printing?
SLA, also called resin printing, is a different way of 3D printing a part. Instead of melting plastic string like our regular (FDM) printers do, it uses a liquid resin that hardens under a light, layer by layer – a bit like curing nail polish, but far more precise.
The big advantage: an extremely smooth, detailed surface with no visible layer lines – much closer to an injection-molded part than a 3D print. The trade-off: parts are more limited in size, and every print needs a quick wash and light-curing step afterwards, which we take care of for you.
Why choose resin over standard printing?
- Smooth finish: no visible layer lines, great for anything that needs to look polished.
- Fine detail: perfect for small or intricate parts – jewelry, miniatures, connectors, parts with tiny features.
- Special materials: we offer resins that behave like real rubber or even real silicone, which regular printing can’t do.
Good to know
Your part arrives fully finished and ready to use – we handle the washing and curing steps ourselves, so there’s nothing extra for you to do.
Resin printers also have a smaller maximum part size than our regular printers. If your part is on the larger side, let us know and we’ll tell you whether resin or standard printing is the better fit.
Materials
We currently offer the following resins, each suited to different needs – from tough engineering parts to true silicone components and optically clear prototypes.
| Material | Strength | Flexibility | Heat resistance | Print difficulty | Best for |
|---|---|---|---|---|---|
| Tough 1500 V2 | Medium | Semi-flexible (PP-like) | ~52°C | Easy | Living hinges, snap-fits, parts that flex repeatedly |
| Tough 2000 V2 | High | Rigid (ABS-like) | ~70°C | Easy | Functional prototypes, enclosures, load-bearing parts |
| Flexible 80A V2 (Black) | – | Very flexible | Tg -49°C | Moderate | Gaskets, soft-touch grips, protective inserts |
| Flexible 80A (Translucent) | – | Flexible | Tg 27°C | Moderate | Translucent flexible parts, tubing mockups |
| Silicone 40A | – | Very flexible (true silicone) | Tg -107°C | Advanced | Seals, wearables, genuine silicone-feel parts |
| Clear Resin V5 | High | Rigid | ~74°C | Easy | Transparent prototypes, light guides, fluidics |
Rigid materials show a heat deflection temperature (the point where they start to bend under load when hot). Flexible and silicone materials don’t have that spec – instead we show their glass transition temperature (Tg): the point where they’d turn stiff and brittle if it got that cold. Lower Tg means the material stays flexible in colder conditions.
Material details
Values below are drawn from published Formlabs technical data sheets. Real-world results vary by print settings, orientation, and post-curing time.
Tough 1500 V2
A flexible-but-tough engineering resin with properties similar to polypropylene (PP) – parts can flex repeatedly without cracking, making it well suited to snap-fit assemblies, living hinges, and parts that need to absorb impact without becoming brittle over time.
Tough 2000 V2
A rigid, ABS-like engineering resin built for demanding functional prototypes and end-use parts. It resists shattering, deformation, and long-term wear, holding up well under both mechanical stress and moderate heat.
Flexible 80A V2 (Black)
A soft-touch, rubber-like elastomer that mimics 80A-durometer cast urethanes and TPU. Parts snap back after bending, twisting, and compression, making it a good match for protective inserts, soft grips, and functional prototypes that need to flex without tearing. This is a newer formulation with improved tear strength and rebound compared to the original Flexible 80A below.
Formlabs has not published full independent datasheet figures for this newer formulation at the time of writing.
Flexible 80A (Translucent)
The original Flexible 80A formulation – a translucent, rubber-like material for prototyping parts normally made from softer rubbers or elastomers. A good option when see-through flexibility is useful, such as for tubing mockups or soft translucent housings.
Silicone 40A
A true 100% silicone 3D printing material – not a silicone-like imitation. It holds its shape and flexibility across a wide temperature range, making it suited to seals, wearable components, and soft parts that need genuine, long-term silicone performance rather than just a rubbery feel.
Clear Resin V5
A rigid, optically clear general-purpose resin for parts where transparency matters – prototypes that need to look and function like clear injection-molded plastic, fluid-flow visualization, lenses, and light guides. Parts can be polished to near-optical clarity as an additional finishing step.
Design Tips & Tolerances
Resin printing has different strengths and constraints than FDM – a few things to keep in mind when preparing your model.
Wall thickness
Walls can generally be thinner than FDM – as little as 0.6 – 1mm for small, well-supported parts. Very thin walls are more fragile until fully post-cured, so handle freshly printed parts carefully.
Hollowing and drain holes
Large solid parts waste resin and can trap stress during curing, so we often hollow out bigger models with a shell of even thickness. Hollowed parts need at least one drain hole so uncured liquid resin can escape from inside during washing – without one, resin gets trapped inside the part. If you’re submitting a hollowed model yourself, let us know its wall thickness so we can check drain holes are placed correctly.
Overhangs & supports
Steep overhangs need support material, similar to FDM, though resin supports are thinner and leave smaller marks where they’re removed. Orientation is chosen to minimize supports on visible or cosmetic surfaces wherever possible.
Dimensional accuracy
SLA is significantly more precise than FDM – typical achievable tolerance is around ±0.15% of a dimension (e.g. ±0.15mm over 100mm), depending on part size, geometry, orientation, and material. If your application needs specific tolerances, let us know before ordering.
Minimum feature size
Fine details reproduce noticeably better than FDM – features down to about 0.3 – 0.5mm are generally achievable, depending on geometry and orientation. Flag any critical small features in your order comments so we can double-check before printing.
Where to Find 3D Model Files
The same model-sharing communities that work for FDM also work for resin printing – any standard STL file can be printed on either process. See our full list of recommended sites on the main Resources page.