Two families, two chemistries
Consumer and prosumer 3D printing splits into two camps. Photopolymer printers, SLA, DLP, and LCD, cure a liquid resin with light, building the part upside down one cured layer at a time. Filament printers, FDM or FFF, melt a solid thermoplastic strand and deposit it through a nozzle, laying down beads that fuse as they cool.
The chemistry drives everything else. Resin starts fluid and becomes solid only where light hits it, so it can resolve tiny features with no nozzle in the way. Filament starts as a solid rod, so its resolution is fundamentally limited by nozzle diameter and how finely the molten bead can be placed.
How SLA, DLP and FDM actually build
In SLA and DLP, a light source, a laser or projector, cures a thin slice of resin across the build platform; the part is lifted, the next layer is exposed, and supports hold the geometry to the build plate. Layer heights of 25 to 50 microns are common, and because there is no tool touching the surface, vertical walls are smooth.
In FDM, the nozzle traces each layer as a continuous bead. Resolution is set by nozzle size, often 0.4 mm, and layer height, commonly 0.1 to 0.3 mm. The bead path leaves visible lines, and overhangs need support material printed from the same or a second filament. The process is mechanical and forgiving but coarser.
Detail, resolution and dimensional accuracy
Resin wins on fine detail. Small text, thin walls, fine holes, and organic sculpted surfaces come out crisp because the pixel or laser spot defines the edge. Tolerances of about plus or minus 0.1 mm are typical, and high-resolution machines push finer. This is why dentistry, jewelry, and miniatures favor resin.
Filament is coarser but perfectly adequate for most functional parts. Expect plus or minus 0.2 to plus or minus 0.5 mm, with accuracy sensitive to temperature, belt tension, and how the part is oriented. Large, blocky fixtures and enclosures print fine; tiny interlocking features may need cleanup or a resin machine instead.
Surface finish and the layer-line problem
A resin part emerging from the vat already has smooth, near-injection-molded surfaces on cured faces, needing only washing and UV post-cure. Curved and detailed surfaces look finished with minimal sanding, which is a major reason for choosing resin for presentation models.
Filament parts show stair-stepping and bead lines, especially on curved or angled surfaces. These can be sanded, filled, or vapor-smoothed for ABS to approach a smooth look, but that is extra labor. For hidden structural brackets the lines are harmless; for visible consumer parts they often need finishing.
Strength, anisotropy and end-use suitability
Standard resin is brittle, strong in compression but it can crack or shatter under impact or bending. Tough and engineering resins, ABS-like, HDT-enhanced, glass-filled, improve this markedly, yet they still generally trail the impact resistance of a well-printed thermoplastic.
Filament parts are tougher and more ductile. ABS, PC, PA, nylon, and carbon- or glass-filled grades absorb impact and resist fatigue far better, and the extruded bead structure gives good in-plane strength. Layer adhesion is the weak axis, so very high through-thickness loads still need design care.
Material range and properties
Resin libraries center on photopolymers: standard, tough, flexible, castable, dental, and high-temperature grades. Each tunes one property, clarity, flexibility, heat deflection, at the cost of others. You get excellent specific traits but a narrower overall property window than molding or filament.
Filament spans a broad thermoplastic menu: PLA for easy prints, ABS and ASA for toughness and heat, PC for clarity and strength, nylon for wear and chemical resistance, and composites with carbon or glass for stiff, light parts. If you need a known engineering plastic, filament usually has it.
Post-processing, safety and mess
Resin is the messier, higher-care process. Printed parts come wet with liquid resin and must be washed in isopropyl alcohol, then UV-cured, and sometimes further sanded or painted. Uncured resin and fumes require gloves, eye protection, and active ventilation; it is a lab-like workflow, not a desk task.
Filament is comparatively clean. Parts are handled dry; you snap or cut away supports and lightly sand if needed. The main safety note is fume control for ABS and ASA and keeping the enclosure ventilated. Setup and cleanup are friendlier for an office or workshop.
Cost per part, material and throughput
Resin machines and resin are moderately priced, but material cost per gram is higher than commodity filament, and the IPA wash and cure add consumables. For small, detailed parts the material used is tiny, so per-part cost stays low; for large solid parts resin gets expensive fast.
Filament is cheap by the spool and efficient for large, mostly-solid parts since you pay for the plastic you extrude. Throughput favors filament for big parts and resin for many small parts on one build platform. Choose by part size and count, not just by machine price.
Lead time and iteration speed
Both are fast from file to part, but the rhythm differs. Resin prints fine details slowly per layer yet packs many small parts in one vat run, so a batch of miniatures finishes efficiently. Washing and curing add a fixed post-step regardless of count.
Filament prints continuously and scales with part volume; a big enclosure may take many hours but needs little post-handling. For a quick functional prototype you can often print, peel supports, and test the same afternoon on filament, while resin needs the wash-cure window.
Typical applications by industry
Resin dominates where looks and detail rule: dental models and surgical guides, jewelry masters, miniatures and figurines, and visual presentation prototypes with smooth surfaces. It is also used for castable patterns in lost-wax metal casting.
Filament dominates where function rules: jigs and fixtures on the factory floor, enclosures and brackets, replacement parts, and large-format prototypes. A carbon-filled nylon bracket on a robot arm is a textbook filament use case that resin would struggle to match on toughness.
How FabProto helps you choose and print
FabProto runs both resin and filament systems, so the choice is based on your part, not on what a single machine can do. Send the model and we will flag whether fine detail, smooth finish, toughness, or size should drive the process.
We can print the same geometry on both to compare, advise on orientation and supports to minimize finishing, and match the material to your end use, whether that is a showroom model in tough resin or a shop-floor jig in carbon-filled nylon. You get the right process without buying both technologies.