Two fundamentally different physical processes both carry the label "3D printing." FDM (Fused Deposition Modeling) melts and extrudes thermoplastic filament. Resin printing (MSLA/SLA) uses ultraviolet light to cure liquid photopolymer. The hardware looks similar from a distance — a machine on a desk that produces objects — but the workflow, output quality, material options, safety requirements, and ideal use cases are profoundly different.
This comparison covers every dimension that matters for making an informed choice between the two technologies.
How Each Technology Works
FDM feeds a spool of solid thermoplastic filament through a heated nozzle, melting it to a semi-liquid state. The nozzle traces each layer of the model in X and Y, depositing molten plastic that bonds to the layer below as it cools. The build plate drops in Z between layers.
MSLA (Masked Stereolithography) — the dominant form of consumer resin printing — works in reverse. The build plate starts at the bottom of a vat filled with liquid resin and rises upward. A UV LCD screen beneath the vat projects the cross-section of each layer, curing only the areas exposed to light. The cured layer adheres to the plate (or the previous layer) as the plate lifts, and the process repeats.
Resolution and Detail Quality
This is where resin wins decisively. An MSLA printer's XY resolution is determined by the pixel size of its LCD screen — typically 0.05 mm (50 microns) or finer on modern machines. Every feature within that resolution is cured simultaneously in a single flash of the UV screen.
FDM resolution is limited by nozzle diameter. The standard 0.4 mm nozzle cannot physically produce features narrower than approximately 0.4 mm. Even with smaller nozzles (0.2 mm), FDM cannot approach the surface smoothness of resin because layer lines are inherently visible on curved surfaces printed in filament.
For miniatures, jewelry masters, dental models, and anything with fine surface texture — resin is unambiguously superior. For mechanical parts with toleranced holes and flat faces — FDM produces excellent results and is generally easier to calibrate for dimensional accuracy.
Build Volume
FDM printers scale readily to large build volumes. Mid-range consumer machines offer 235 × 235 × 250 mm as a starting point; large-format printers reach 400 × 400 × 500 mm and beyond. Printing a large vase, a prop helmet, or a structural mechanical assembly is straightforward.
Consumer resin printers are typically constrained to smaller build volumes — commonly 150 × 80 × 165 mm to 200 × 120 × 260 mm — because larger LCD screens are expensive, higher-power UV light sources are required to cure uniformly across a large area, and the vat of liquid resin becomes heavier and more difficult to manage. Large-format resin printers exist but occupy a professional price tier.
Print Speed
Modern high-speed FDM printers (Bambu Lab, Creality K1, Qidi X-Max) print at 300–600 mm/s, completing small-to-medium objects in under an hour. The layer-by-layer extrusion time scales with object volume.
MSLA resin printers have a unique speed characteristic: each layer takes the same time regardless of how many objects are on the build plate, because the entire layer is cured in one UV exposure. This makes resin printers highly efficient when batch-printing many small objects simultaneously. However, for a single large object occupying the full build volume, resin layer count and peel forces make total print time competitive with but not dramatically faster than FDM.
Material Range
FDM materials are extraordinarily diverse: PLA, PETG, ABS, ASA, TPU, Nylon, carbon fiber composites, wood-fill, metal-fill, PEEK, and more. Mechanical properties span a huge range, from soft rubber to near-metal stiffness. Most materials are food-safe in their raw form and do not require special handling beyond ventilation for high-temperature variants.
Resin materials have expanded significantly but remain in a narrower functional range. Standard resins are brittle and not UV-stable; engineering resins add toughness, flexibility, or heat resistance; specialized formulations target dental, casting (burnout), and water-washable applications. All liquid resins are skin and eye irritants before curing and require careful handling with gloves and eye protection. Uncured resin disposal requires UV exposure before it can be treated as standard waste.
Post-Processing Requirements
FDM post-processing is optional. A well-tuned FDM print can come off the bed, have supports removed, and be considered finished. Sanding, painting, and surface treatment improve aesthetics but are not mandatory.
Resin post-processing is mandatory and multi-step:
- Washing: Freshly printed resin parts are coated in liquid uncured resin. They must be washed in isopropyl alcohol (IPA) or a dedicated wash solution for several minutes to remove surface resin.
- UV curing: After washing, parts are placed in a UV curing station for several minutes. This completes the photopolymerization, reaching the final mechanical properties. Parts that are not post-cured remain tacky and underperform mechanically.
- Support removal: Resin supports are typically thinner and cleaner than FDM supports but can leave small marks that require sanding.
The washing and curing steps add 15–30 minutes to every resin print and require dedicated equipment (wash and cure station, IPA supply) and a space where resin spills can be managed safely.
Cost Analysis
Entry-level machines in both categories now cost under $300. However, the total cost of ownership differs:
- Filament costs €15–€40 per kilogram for standard materials. A kilogram prints a very substantial number of parts. Cost per gram is low.
- Resin costs €25–€60 per kilogram for standard materials, with engineering resins substantially more. Resin also requires ongoing IPA or wash solution replacement, FEP/nFEP release film replacement (the transparent membrane at the bottom of the vat wears out), and LCD screen replacement every few hundred hours on high-use machines.
For most users, FDM has a lower total running cost. Resin's higher consumable overhead is justified when the resolution is specifically required.
The Clear Recommendation Framework
Choose FDM if you need:
- Functional mechanical parts with good strength
- Large objects that don't fit a small resin build volume
- Minimal post-processing and workspace requirements
- Flexible materials (TPU), heat-resistant materials (ASA/ABS), or engineering polymers
- Low filament cost for high-volume printing
Choose Resin if you need:
- Ultra-fine surface detail (miniatures, jewelry, dental models)
- Smooth surfaces without visible layer lines
- Small, highly detailed objects in batch quantities
- Castable masters for lost-wax metal casting
Many serious makers end up with both technologies — an FDM printer for functional parts and structural work, and a resin printer for detail work and display pieces. The two technologies are complementary rather than competitive.