The Core Difference

FDM (Fused Deposition Modeling) works by melting and extruding plastic filament layer by layer onto a build plate. Resin printing (SLA/MSLA) uses UV light to cure photopolymer resin layer by layer into solid geometry.

Same high-level concept, completely different execution, with dramatically different results in surface quality, material properties, and ideal use cases.

FDM: What It Does Well

FDM is the workhorse of prototyping. Its strengths are material variety, build volume, structural integrity, and cost at scale.

  • Materials: PLA, PETG, ABS, ASA, TPU (flexible), Nylon, PC, HIPS, each with distinct mechanical and thermal properties for different applications.
  • Build volume: FDM printers routinely handle 256×256×256mm and larger. Enclosures, housings, brackets, and large prototypes are all in range.
  • Post-processing: Sand, prime, paint, tap threads, or insert heat-set inserts. FDM parts integrate naturally into assembly and production workflows.
  • Cost efficiency: For larger parts, FDM is almost always cheaper per unit volume than resin.

FDM: The Tradeoffs

Layer lines are the perennial critique of FDM, and the criticism is legitimate. Without sanding and priming, FDM surfaces show horizontal banding at 0.1–0.3mm layer height. Fine details below 1mm often don't resolve cleanly, and text at small scales can be illegible.

Overhangs beyond 45° require support structures, which leave witness marks and add cleanup time. For parts with complex internal geometry or very fine features, FDM hits real limits.

Resin: What It Does Well

Resin printing's defining strength is surface quality and fine feature resolution. UV-cured resins resolve features well below 0.1mm. Layer heights are typically 0.025–0.05mm, producing surfaces that often require no post-processing for visual or presentation applications.

  • Detail: Jewelry mockups, dental models, miniatures, product prototypes with fine logos, lettering, or texture.
  • Surface quality: Out of the printer and after washing, resin parts look polished. Ideal for client presentations and photorealistic mock-ups.
  • Dimensional accuracy: Resin typically holds tighter tolerances than FDM for small and intricate parts.

Resin: The Tradeoffs

Standard resin parts are more brittle than most FDM materials. ABS-like resin snaps under impact where PETG or ABS filament would flex or deform. Functional parts subject to mechanical stress, such as clips, snap-fits, and load-bearing brackets, are generally a poor fit for standard resins.

Build volume is smaller (most machines cap around 130×80×160mm), cost per volume is higher, and post-processing requires IPA washing and UV curing, adding equipment and time to your workflow.

Tip: Engineering resins (ABS-like, tough resin, flexible resin) close some of the mechanical gap, but they're still more brittle than FDM filaments in most real-world use cases.

Choose FDM When

  • Your part is functional: brackets, enclosures, jigs, fixtures, or anything load-bearing
  • You need a specific engineering material: flexible (TPU), heat-resistant (ABS/ASA), or chemically resistant (Nylon)
  • The part is larger than roughly 100mm in any key dimension
  • Cost per part matters more than pristine surface finish
  • You need multiple units across different colors or materials

Choose Resin When

  • Surface quality and fine detail are the primary requirements (product mock-ups, display models)
  • You're printing small, precise components with intricate geometry
  • The part won't bear significant mechanical load or repeated stress
  • You need a smooth, paintable surface without post-processing
  • You're working in dental, jewelry, or high-detail miniature applications

Making the Right Call

When in doubt: if it's going on a shelf or into a client presentation, consider resin. If it's going into an assembly or needs to survive handling, use FDM. For structural engineering parts, FDM with the right material wins almost every time.

Still unsure? When you configure your order on Piclaro, you'll see both options with a clear comparison of strength, resolution, and pricing for your specific geometry, so you can make the choice with real data.