Key takeaways
- Resolution and strength are different axes. Resin wins the first; FDM and SLS share the second.
- Resin isn't "weak": Formlabs publishes 65 MPa tensile strength after UV cure, higher than many filaments. What it lacks is elongation and heat resistance.
- SLS is anisotropic too, just far less than FDM. The published figures are 11 % elongation in X/Y against 6 % in Z.
- Don't compare numbers across data sheets that use different test standards. ISO 527 and ASTM D638 don't give the same number on the same material.
These three technologies are often ranked by "how advanced" they are, as if SLS beats resin and resin beats FDM. They can't be ranked that way. They shape material in three different ways, and each leaves its own fingerprint on the part — and that fingerprint is what decides where your part belongs.
Three ways of making a shape
One file, three ways to turn it into an object
- FDM (filament)
- A bead of molten plastic is laid beside and on top of the previous one. The part is a collection of welds, so print orientation is a mechanical parameter.
- Resin MSLA / DLP
- A whole layer is exposed at once through an LCD screen, and liquid resin cures in place. Print time depends on the part's height, not the number of parts on the plate.
- SLS (selective laser sintering)
- A laser sinters nylon powder in a heated chamber. Unsintered powder supports the part, so no supports are needed and even nested mechanisms can be printed.
Resolution: 0.48 mm against 14 µm
This is the biggest gap between FDM and resin, and it is geometry, not machine quality. A 0.4 mm nozzle lays a line about 0.48 mm wide; no tuning makes that line much narrower. A 16K screen on a desktop resin printer has pixels around 14 × 19 µm — roughly thirty times smaller in one dimension.
| FDM 0.4 mm | Resin MSLA 16K | |
|---|---|---|
| Smallest in-plane unit | ≈ 480 µm (line width) | 14 × 19 µm (pixel) |
| Typical layer height | 120–240 µm | 20–50 µm |
| Reference build volume | 256 × 256 × 256 mm (Bambu Lab A1) | 211.68 × 118.37 × 220 mm |
| Time depends on | Number of parts and volume of plastic | Part height, not number of parts |
The last row is what newcomers rarely expect: on a resin printer, one figurine or ten of the same height take almost the same time. That is why model workshops run resin in full-plate batches.
Mechanical properties: three data sheets side by side
| PLA (FDM) | PETG (FDM) | Standard resin | PA12 (SLS) | |
|---|---|---|---|---|
| Tensile strength | 46.0 MPa | 37.9–50.8 MPa | 65 MPa | 50 MPa |
| Tensile modulus | not published | 2,117 MPa | 2,800 MPa | 1,850 MPa |
| Elongation at break | not published | 8.4 % | 6 % | 11 % (X/Y) · 6 % (Z) |
| HDT 0.45 MPa | 53 °C | 76–78 °C | 73 °C | 171 °C |
We left impact out of the table entirely, because it can't share a row: the ISO standard reports energy per area (kJ/m²) and the ASTM standard per specimen width (J/m). The units don't convert, so putting 5.0 kJ/m² next to 25 J/m creates a comparison that doesn't exist. Each material's impact figure is on its own data sheet.
This table breaks two assumptions at once. First, resin is not weak: 65 MPa tensile beats PLA and matches good PETG. Second, SLS PA12 doesn't win on tensile strength — it wins on heat ceiling, by a mile: 171 °C against 73 °C. If your part gets hot, that's the only row that matters.
There's one more column a resin data sheet has to publish and few people read: the part before UV cure. Formlabs publishes 38 MPa for a freshly printed part against 65 MPa after curing — nearly half. Skip the cure and you've printed a different material.
What each technology can't do
FDM: orientation is a mechanical property
Across the layers, an FDM part typically reaches only 30–50 % of its in-plane strength. That gap is larger than the gap between any two plastics, so turning the part on the plate does more than changing material. Details in print settings for strength.
Resin: beautiful parts, messy process
Parts come off the machine still wet with liquid resin and must be washed in isopropyl alcohol and then UV-cured. Liquid resin irritates skin and needs gloves; used wash alcohol is waste, not something for the sink. After that there are still two material limits: 6 % elongation means the part snaps rather than bends, and an HDT of 73 °C means it doesn't belong in a car. Settings and process for resin are on the resin catalogue page.
SLS: no desktop machines
SLS needs a heated chamber, inert gas or oxygen control, and a powder-handling process. The machines are industrial-class, and recovered powder must be blended with fresh powder in a set ratio. In Vietnam it is an outsourced service: you send a file, you receive parts. In exchange, it is the only one of the three that gives near-isotropic parts without supports — hinges, nested joints and hollow lattices in a single print.
Resin wins the first millimetre. FDM wins the first kilogram. SLS wins the part whose supports could never come out.
Money: machines, material, and where to buy
List prices observed at one Vietnamese retailer on 27/08/2026, as a reference scale rather than a quote: the enclosed Bambu Lab P1S FDM printer at 9,359,000 VND, the multi-colour A2L FDM printer at 11,499,000 VND, the Anycubic Photon P1 resin printer at 16,345,000 VND, and the large-format ELEGOO Jupiter 2 16K resin printer at 23,100,000 VND. Machine prices move faster than filament prices. See sources.
- FDM — the lowest material cost per gram, and the only technology with a wide engineering range: PETG, ABS, ASA, nylon, PC, fibre-filled composites.
- Resin — cheap per small part, plus wash alcohol, gloves, FEP film and an LCD screen as consumables with a lifetime.
- SLS — priced per part when outsourced; sensible from a few dozen parts up, expensive for a one-off.
How to break down the real cost on your own machine — material, electricity, machine hours, labour and failure rate — is in how to calculate 3D printing cost along with the print cost calculator.
Choose by the part, not by the machine
Where your part belongs
- Fixtures, housings, indoor mechanical parts
- FDM, PLA or PETG
- Heat-exposed parts in a car or outdoors
- FDM, ASA or PA — not resin
- Models, figurines, features under 1 mm
- Resin MSLA
- Dental models, casting patterns, glossy surfaces
- Resin, a specialist grade
- Hinges, nested joints, lattices whose supports can't come out
- SLS, outsourced
- Batches of a few dozen identical nylon parts
- SLS, and compare prices with FDM PA12 before deciding
If you've settled on FDM and are choosing a printer, what can my 3D printer print covers the four deciding numbers, and 3D printer makers compared covers where each maker is strong.
Frequently asked
Can a resin printer make functional parts?
Yes, within narrow limits. Standard resin reaches 65 MPa tensile but only 6 % elongation and an HDT of 73 °C at 0.45 MPa, so parts are stiff and snap rather than bend, and soften early when hot. There are tough and high-temperature resins, but they cost more and still don't replace nylon for impact parts.
Is SLS printing really isotropic?
Not completely, and the data sheet says so. Formlabs publishes 11 % elongation in X/Y and 6 % in Z for SLS PA12. That is still anisotropy — just far less than FDM's 30–50 % gap. For parts loaded in many directions, that difference is worth paying for.
Should I buy both an FDM and a resin printer?
If you make both functional parts and models, yes, and it's usually more sensible than buying one more expensive FDM printer. The two machines solve problems that don't overlap. But count the space: a resin printer needs a washing area, ventilation and somewhere to store alcohol — more than the footprint of the machine itself.
Can resin parts be used outdoors?
No. Photopolymer keeps reacting under UV, so parts embrittle and discolour after weeks to months of sun. For outdoor parts in a tropical climate, ASA is the answer — background in 3D printing for outdoor use.
Do SLS nylon powder and PA12 filament give the same part?
Same polymer family, different process, so different results. The SLS version is near-isotropic with no layer lines; the FDM version has weaker layer planes but can be printed in your own workshop and is cheaper for one or two parts. If you need uniform properties in every direction, the process matters more than the material name.