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FDM vs SLA: which 3D printing process should you use?
A plain-English comparison from the shop that runs both, so you can pick the right process before you upload a file.
Choose FDM for strong, functional parts in engineering plastics like nylon, carbon-fiber nylon and ASA, and for larger parts at a lower cost. Choose SLA when you need fine detail, smooth surfaces and tight tolerances — looks-like models, small precise parts and casting patterns. At Mithril, most parts from either process ship in 3–5 days.
How each process works
FDM (fused deposition modeling) melts plastic filament and lays it down one layer at a time. Because it uses real thermoplastics, parts behave much like the material they're made of — tough, heat-tolerant and ready for threaded inserts.
SLA (stereolithography) uses a laser to cure liquid resin one very thin layer at a time. The result is a smooth, highly detailed part with crisp edges and small features that FDM can't reproduce.
FDM vs SLA at a glance
| FDM | SLA | |
|---|---|---|
| Strength & toughness | Strong in engineering plastics; best for loaded and functional parts | Good with tough and durable resins; generally less impact-resistant |
| Surface finish | Visible layer lines | Smooth, near-molded look |
| Detail & tolerances | Good for most functional features | Excellent for fine features and tight tolerances |
| Part size & cost | Economical for larger parts | Best value on small to medium parts |
| Materials | PLA, ABS, ASA, PETG, nylon, carbon-fiber nylon, TPU | Standard, tough, durable, clear, castable and Silicone 40A resins |
| Outdoor use | ASA holds up well in sun | Most resins aren't made for long UV exposure |
| Typical lead time | 3–5 days | 3–5 days |
Choose FDM when…
- The part carries load, flexes or takes impact (brackets, clips, fixtures).
- It's large, or you need several and cost matters.
- It lives outdoors or near heat.
- You need metal threads — we install heat-set threaded inserts in FDM parts.
Choose SLA when…
- Appearance matters: design reviews, pitches, display models.
- The part is small with fine features or tight-fitting details.
- You need a clear part, a soft silicone-like part, or a casting pattern.
Still not sure?
Upload your file to the instant quote to see FDM and SLA pricing side by side, or tell us what the part has to do and an engineer will recommend one. Our materials guide compares every plastic and resin we offer.
Questions
Is SLA stronger than FDM?
Usually not. For parts that carry load or take impact, FDM in nylon or carbon-fiber nylon is typically the stronger choice. SLA's tough and durable resins close some of the gap, but SLA's real advantages are detail and finish.
Which is cheaper, FDM or SLA?
FDM is generally cheaper, especially for larger parts. The instant quote shows both prices for your exact file.
Can SLA parts be used outdoors?
Most resins aren't designed for long exposure to sunlight. For outdoor parts we usually recommend FDM in ASA.
Can I get threaded inserts in a printed part?
Yes — we install heat-set threaded inserts in FDM parts, so they arrive with metal threads ready for assembly.
Get FDM and SLA pricing in seconds
Upload STL, OBJ, PLY, GLB or GLTF files and compare both processes for your part.