Choosing the wrong printing process is the single most expensive mistake product teams make when commissioning 3D printed parts. A bracket that ships beautifully in SLA will crack in three days under load — because SLA is optimised for resolution, not impact strength. Here is the definitive decision guide from the engineers at Layer X who run FDM, SLA, and SLS machines daily in Ahmedabad.
FDM (Fused Deposition Modelling)
FDM is the workhorse of additive manufacturing. A nozzle melts thermoplastic filament and deposits it layer by layer. The process is fast, inexpensive, and produces parts in production-grade materials — PLA, PETG, ABS, ASA, PC, PA-CF, and more.
Best for: functional prototypes, jigs and fixtures, enclosures, large structural parts, low-volume production runs where surface finish is secondary to cost and speed.
Tolerances at Layer X: ±0.3 mm standard; ±0.2 mm in engineering-grade materials. Build volume 300×300×400 mm. Lead time 3–5 days from ₹400/part.
Limitations: Visible layer lines require post-processing for smooth surfaces. Anisotropy — parts are weaker in the Z-axis. Not suitable for fine jewellery or dental work.
SLA (Stereolithography)
SLA cures photopolymer resin with a UV laser. The result is exceptional surface quality and the finest feature resolution of any desktop-scale process — routinely below 0.1 mm. Castable resins allow direct investment casting of metal parts from 3D printed positives.
Best for: visual prototypes requiring smooth surfaces, master patterns for silicone moulds, dental and jewellery applications, microfluidic channels, parts with intricate overhangs.
Tolerances at Layer X: ±0.1 mm standard; ±0.05 mm in dental/castable grade. Build volume 192×120×245 mm. Lead time 2–4 days from ₹800/part.
Limitations: Photopolymers degrade under UV exposure over time. Impact resistance is lower than FDM thermoplastics. Resin is brittle — avoid thin snap-fit clips.
SLS (Selective Laser Sintering)
SLS fuses nylon powder with a CO₂ laser. No supports are needed — unfused powder holds the part — which opens up complex internal channels, living hinges, and interlocking assemblies impossible in supported processes.
Best for: functional end-use parts, complex geometries with undercuts, assemblies printed-in-place, small production runs in PA12, PA11, or glass-filled nylon.
Tolerances at Layer X: ±0.2 mm standard. Natural surface has a matte, slightly granular finish. Lead time 4–6 days from ₹1,200/part.
Limitations: Minimum wall 0.7 mm. Parts have slight porosity — seal if fluid-tight is required. Colour options limited without dyeing post-process.
Quick Selection Table
| Criterion | FDM | SLA | SLS |
|---|---|---|---|
| Starting price | ₹400 | ₹800 | ₹1,200 |
| Tolerance | ±0.2–0.3 mm | ±0.05–0.1 mm | ±0.2 mm |
| Surface quality | Medium | Excellent | Good (matte) |
| Mechanical strength | High | Medium | High (isotropic) |
| Supports needed? | Yes | Yes | No |
Our Recommendation
If you are unsure, default to FDM for first-article testing and SLA for any part that will be photographed or cast. Once geometry is validated and you need isotropic strength with no support constraints, move to SLS. Layer X runs all three processes under one roof — upload your STL and get quotes for all three simultaneously.