Guide · Process Selection
SLA vs FDM vs SLS: choosing the right process without a materials degree
Three technologies, three personalities, one recurring client question. Here's the honest decision guide we give over email every week — written down properly.
Every week someone asks us to settle the same argument: which printing process is “best.” The honest answer is that the question is malformed — processes aren't ranked, they're cast. Each one is the star of a different movie. Here's the typecasting.
FDM: cast it when speed and budget lead
Fused deposition modeling extrudes melted thermoplastic along toolpaths. It's the least expensive process per part, the fastest to start, and its materials — PLA, PETG, ABS, TPU — cover an enormous functional range. The tell-tale layer lines are its signature and its tradeoff: fine for brackets and iterations, wrong for beauty shots.
Cast FDM for: early design iterations, jigs and fixtures, enclosures, anything large and light, and every prototype whose job is to answer a question rather than win an award.
SLA: cast it when the surface is the story
Stereolithography cures liquid resin with a laser at layer heights down to 25 microns — an order of magnitude finer than typical FDM. Parts emerge smooth, crisp and camera-ready, in resins tuned for detail, toughness, transparency or skin contact.
Cast SLA for: presentation prototypes, architectural and product models, casting masters, clear components, and any part where a client, buyer or camera will lean in close.
SLS: cast it when the part has a real job
Selective laser sintering fuses nylon powder, with the unfused powder acting as built-in support. That means no support scars, near-uniform strength in all directions, and geometric freedom — hinges printed pre-assembled, internal channels, weight-saving lattices. The finish is a consistent professional matte.
Cast SLS for: end-use components, functional prototypes that must behave like molded plastic, complex assemblies, and low-volume production where part #500 has to match part #5.
The 30-second decision tree
- Judged by eyes or camera? → SLA.
- Judged by function under stress? → SLS.
- Judged by tomorrow's deadline or this month's budget? → FDM.
- Genuinely torn? → the part is probably mid-development: iterate in FDM, validate in SLS, present in SLA.
The two classic (expensive) mistakes
Mistake one: paying SLA prices for a bracket nobody will ever look at. Mistake two: printing a client-facing model in FDM to save a little, then spending an evening sanding it into apology-grade. Matching the process to the part's audience — eyes, hands, or calendar — prevents both.
If you'd rather not memorize any of this: our quote form has a “not sure — recommend for me” option for exactly this reason, and it's the most-clicked choice on the site. Questions about a specific part? Send it over — process advice is free and we enjoy the puzzle.
Still torn between two processes?
Upload the file, pick “not sure,” and let the people who run all three machines make the call with you.