Filament and resin printers are the two most common ways to make plastic parts on a desk, and they belong to different process families. A filament printer, called FDM or FFF, pushes a thermoplastic strand through a heated nozzle and lays it down as lines. A resin printer uses light to harden liquid photopolymer one layer at a time. Formlabs groups laser SLA, DLP projection and LCD-masked MSLA printers under the resin heading.
That one difference shapes almost everything else: how small a feature can be, how the surface looks, how the part behaves under load, what happens after printing, and what precautions the workspace needs. This page compares the two on those points. Separate guides cover choosing a process for a project and the differences between resin light engines.
How each builds a layer
In FFF, the printer feeds filament, typically 1.75 mm and occasionally 2.85 mm in diameter according to Prusa, through a hot nozzle and traces each layer as extruded lines that cool on the build plate. The nozzle has to visit every line, so layer height is the main lever on print time. Prusa says taller layers print faster but show more visible lines, and that layer height should stay below about 80 percent of the nozzle diameter, roughly 0.32 mm for a 0.4 mm nozzle.
In a resin printer, the build platform dips into a vat of photopolymer and light cures a thin slice wherever the part should be. Laser SLA traces each layer with a moving spot, so Prusa notes that adding more objects lengthens the print. MSLA and DLP machines expose a whole layer at once, so each layer takes about the same time however many parts are on the platform. Prusa lists layer heights of 25 to 100 microns for SLA printing.
Detail and surface finish
Formlabs' design guidance shows the gap in minimum feature size. It suggests walls of about 0.8 mm for FDM but as thin as 0.2 mm on its Form 4 resin printer, and embossed details about 0.6 mm wide on FDM against 0.1 mm on resin. Prusa calls resin prints almost perfectly smooth and incredibly detailed, with layers that are nearly invisible. Formlabs describes FDM surfaces as having visible layer lines that usually need sanding or smoothing for demanding uses, and says clear resins can print almost fully transparent.
On a filament printer, layer height sets only vertical resolution. Prusa points to a smaller nozzle for finer horizontal detail. On a resin printer, horizontal detail comes from the light engine, which is why spec sheets quote laser spot size, projector resolution or LCD pixel pitch. Formlabs rates its Form 4 at ±0.15 percent for features of 1 to 30 mm, with a lower limit of ±0.02 mm, and says FDM accuracy is limited by how consistently material is extruded and by thermal warping.
Strength and materials
The two processes join layers differently. Formlabs explains that FDM parts are anisotropic: the bond between layers is weaker than the extruded lines, and voids can form between them. Resin layers keep reactive groups that bond chemically to the next layer, so Formlabs describes cured resin parts as highly isotropic. It cites a University of Rhode Island test of underwater enclosures in which FDM housings failed within seconds while SLA housings stayed watertight at very high pressure.
Material range runs the other way. Filament printers use common thermoplastics. Ultimaker lists PLA, ABS, nylon, PETG, CPE, polycarbonate, TPU, polypropylene and water-soluble PVA, plus composites filled with carbon, glass or metal fibers, though it warns that abrasive composites wear some hardware. Formlabs adds PEEK and ULTEM, which generally need professional machines. Resins are proprietary formulations, and Formlabs says it offers more than 40, including flame-retardant, electrostatic dissipative, ceramic-filled and biocompatible grades.
Workflow and post-processing
Both workflows start with a model exported as STL or OBJ and a slicer that adds supports where needed. On a filament printer, supports hold up overhangs. PrusaSlicer offers grid, snug and organic styles and notes that supports can leave small blemishes where they touch the model. Ultimaker adds that water-soluble PVA can support overhangs and cavities on printers that run two materials. Once supports are off, a filament part is ready to use, and Formlabs says the remaining work is mostly sanding away support marks.
Resin parts come off the platform soft and sticky, as Prusa puts it, and need two more steps: washing in isopropyl alcohol or another solvent to remove uncured resin, then post-curing under UV light. Supports matter more, too. Formlabs explains that they hold the model in place for the whole print through a raft, scaffolding and touchpoints, and that under-supported models can leave cured debris floating in the tank or form a pancake on its floor. Formlabs says washing and curing can be automated, while most of the labor in FDM goes to sanding and support removal.
Safety and ventilation
Both processes give off emissions, but the main hazards differ. NIOSH says heating filament breaks the plastic down into particles, often smaller than 100 nanometers, and gases, and that the particles can reach deep into the lungs. It recommends a well-ventilated space, a printer with built-in filtration for particles and gases where possible, and lower-emitting plastics, noting that PLA often releases fewer particles than ABS.
With resin, the liquid itself is the bigger concern. NIOSH's January 2025 guidance says uncured resin contains acrylates and other chemicals that can cause asthma or dermatitis, that printing releases gases, and that washing in isopropyl alcohol raises concerns for lung irritation and dermatitis. It recommends ventilation or filtration, gloves that resist acrylates and IPA and are changed often, UV eye protection, and quick cleanup of drips. Waste is handled differently as well. Formlabs says liquid resin and resin-laden solvent must not go down the drain or into household trash, small amounts of resin should be fully cured before disposal, and cured parts can go in household waste.
Running costs side by side
Formlabs, which makes resin and powder printers, gives these price ranges in its comparison. Budget filament printers and kits start around $200, professional desktop models cost $2,000 to $8,000, and industrial systems start at $15,000. Low-cost resin printers cost about $200 to $1,000 and professional ones $2,500 to $10,000. For materials, it puts ABS and PLA filament from about $30 per kilogram and engineering filaments at $100 to $150 per kilogram, against $100 to $200 per liter for standard and engineering resins and $200 to $500 per liter for biocompatible resins. Resin printing also consumes solvent, gloves and replaceable parts such as tanks and LCD screens.
| Factor | Filament (FDM or FFF) | Resin (SLA, MSLA or DLP) |
|---|---|---|
| How a layer forms | A heated nozzle extrudes thermoplastic lines | Light cures liquid photopolymer |
| Layer height guidance | Below about 80% of nozzle diameter; Prusa advises against going under 0.10 mm | 25 to 100 microns, per Prusa |
| Minimum wall, per Formlabs | About 0.8 mm | As thin as 0.2 mm on Form 4 |
| Surface as printed | Visible layer lines | Smooth, with nearly invisible layers |
| Layer bonding | Anisotropic; weaker between layers | Highly isotropic, per Formlabs |
| After printing | Remove supports and sand | Wash in solvent, post-cure, remove supports |
| Main exposure concerns, per NIOSH | Particles and gases from heated plastic | Skin contact with uncured resin, gases and solvent vapors |
| Entry-level printer price, per Formlabs | From about $200 | About $200 to $1,000 |
| Material price, per Formlabs | From about $30/kg for PLA or ABS | $100 to $200/L for standard resins |
At a glance
Strengths
- Choose filament for larger, low-cost parts in common thermoplastics such as PLA, PETG, ABS and nylon
- Choose filament when parts should be usable straight off the printer after support removal
- Choose resin for fine detail, thin walls and smooth surfaces
- Choose resin when a part must be watertight or behave the same in every direction
Limitations
- Filament: visible layer lines and weaker bonding between layers
- Filament: heated plastic releases particles and gases, so ventilation matters
- Resin: every part needs washing and post-curing
- Resin: uncured resin is a skin and breathing hazard and must not go down the drain
Typical applications
- Filament: prototypes, jigs, replacement parts and short-run end-use parts, per Ultimaker
- Filament: classroom and university projects
- Resin: dental models and other parts that need tight accuracy, per Formlabs
- Resin: watertight housings and clear parts
Materials for this process
- PLA
- PETG
- ABS
- ASA
- TPU / flexible filament
- Nylon / polyamide
- Polycarbonate blends
- Fiber-filled composites
- PVA / BVOH supports
- General-purpose photopolymer resin
- Engineering photopolymer resin
- Tough resin
- Flexible resin
- Clear resin
Common questions
Are resin prints stronger than filament prints?
Not as a rule. Formlabs explains that resin parts are highly isotropic because layers bond chemically, while FDM parts are weakest between layers. But strength depends heavily on the material: tough or engineering resins and filaments such as nylon or polycarbonate behave very differently from standard grades. Compare data sheets for the exact materials, printed in the orientation you plan to use.
Do resin printers need more ventilation than filament printers?
Both need it. NIOSH recommends ventilation or filtration for filament printers because heated plastic releases fine particles and gases, and for resin printers because printing, washing and curing release gases and vapors. Resin adds a skin-contact hazard, so NIOSH also recommends gloves that resist acrylates and IPA, plus UV eye protection.
Which is cheaper to run?
By Formlabs' figures, entry-level printers of both types start around $200, but filament costs less per unit of material: from about $30 per kilogram for PLA or ABS, against $100 to $200 per liter for standard resin.
Can I skip washing and curing resin prints?
No. Prusa notes that resin prints come off the printer soft and sticky and recommends washing them in isopropyl alcohol and curing them under UV light. NIOSH adds that once curing is complete, the resin on the surface is usually fully cured, which greatly reduces the risk of allergic dermatitis.
Sources
- Types of printers and their differences Prusa Research · Checked 2026-11-02
- Layers and perimeters Prusa Research · Checked 2026-10-15
- FDM vs. SLA vs. SLS: How to choose the right 3D printing technology Formlabs · Checked 2026-11-02
- What is FFF 3D printing? UltiMaker · Checked 2026-11-02
- Support material Prusa Research · Checked 2026-10-15
- How supports work in SLA printing Formlabs · Checked 2026-10-15
- Safe 3-D Printing CDC / NIOSH · Checked 2026-10-15
- Safe Desktop Vat Photopolymerization 3-D Printing CDC / NIOSH · Checked 2026-10-15
- Disposing of resin Formlabs · Checked 2026-10-15
- Guide to Resin 3D Printers: SLA vs. DLP vs. MSLA vs. LCD Formlabs · Checked 2026-11-02
An explainer synthesized from the cited references, not hands-on testing. Vendor names for processes are trademarks of their owners and are mapped to the ISO/ASTM 52900 families for orientation.