FDM vs Resin: How 3D Printing Technologies Work
How FDM works
FDM (Fused Deposition Modeling) melts a spool of plastic filament and extrudes it through a heated nozzle, building objects layer by layer from the bottom up. Think of it like a very precise hot glue gun controlled by a computer. The nozzle moves in X and Y while the build plate drops in Z after each layer. FDM printers can use dozens of different materials — PLA, PETG, ABS, nylon, TPU, and more — each with different properties.
How resin (SLA/MSLA) works
Resin printers work by curing liquid photopolymer resin with UV light. MSLA (Masked Stereolithography) — the most common consumer type — uses an LCD screen to mask UV light, curing an entire layer at once. The build plate dips into a vat of liquid resin, the LCD projects a cross-section of the model, UV light cures that layer, and the plate lifts. Because the entire layer cures simultaneously, print time depends on height, not on how many objects are on the plate.
Resolution and detail
Resin wins on detail. MSLA printers achieve 18-40 micron XY resolution, while FDM is limited by nozzle diameter (typically 400 microns). On a 28mm miniature, resin reproduces facial features and armor details that FDM physically cannot resolve. For large decorative pieces or functional parts, FDM's layer lines are usually acceptable and can be sanded smooth.
Strength and materials
FDM wins on strength. PETG, nylon, and polycarbonate are strong engineering materials available only to FDM printers. Standard resin is brittle — fine for display pieces but unsuitable for mechanical loads. ABS-like resin improves toughness but still doesn't match FDM engineering materials.
Safety and handling
FDM with PLA is essentially odorless and non-toxic — safe for living spaces and classrooms. Resin requires nitrile gloves (skin sensitizer), ventilation (fumes), and careful waste disposal (uncured resin is hazardous). Never handle uncured resin with bare skin. This makes FDM the clear choice for homes with children or pets.
Post-processing
FDM prints are ready to use immediately — just remove supports if any. Resin prints require washing (IPA or water for water-washable resin), UV curing, and support removal. The entire post-processing workflow adds 15-30 minutes per batch and requires dedicated supplies.
Cost comparison
FDM filament costs $18-30/kg. Resin costs $25-55/L. Per-unit costs depend heavily on the object: a 28mm miniature uses 3-5ml of resin ($0.10-0.25) — cheaper than printing the same mini in FDM when you account for time and waste. Large objects are significantly cheaper in FDM due to lower material costs per volume.