September 27, 2020
fdm vs sla 3d printing comparison guide cover

FDM vs SLA 3D Printing: Which Is Best For You?

Fused deposition modeling (FDM) and Stereolithograpy (SLA) are two of the most commonly used and well-known 3D printing technologies. But which is better?

This guide is also part of our FREE 3D printing technologies EBook. You can download it here.

History of Stereolithography and Fused Deposition Modeling

SLA was the first 3D printing technology available — all the way back in 1987 when 3D Systems released the SLA-1 3D printer. The patents for FDM were filed back two years later in 1989, though both patents have since expired allowing cheaper consumer printers to come to market.

sla 3d printing patent
The first 3D printing patent back in the 1980s.

FDM vs SLA Printing Process

Fused deposition modeling involves heating the 3D printer filament — such as ABS, PLA or PETG — until it melts, and extruding the material in layers (according to the 3D printer model, or STL file) to gradually create a finished part.

An easy way to visualize this is in icing a cake — you extrude the icing out of the piping in accordance to the design you want. If this design involves anything three-dimensional, then you draw your first layer, and then layer more icing on top. This is exactly what happens with FDM 3D printing.

Stereolithography 3D printing also involves printing layer by layer, but instead of physically touching the material it prints it instead cures the resin with a UV light or projector (DLP). The light laser is shone on to the resin, curing the area intended whilst leaving the rest liquid, and repeated layer-by-layer until the model is finished.

Stereolithography and Digital Light Processing and slightly different variations of this technology. DLP instead involves projecting the entire layer’s dimensions at the same time rather than on one particular spot, and is often faster.

SLA stereolithography process
The stereolithography 3D printing process.

Print Time and Speed

In terms of FDM vs SLA print speed, this depends on the quality and infill specifications. You can print faster with FDM if you are willing to sacrifice quality, though go too fast and your model could end up looking like an intelligible splodge. Assuming normal print specs, there isn’t a huge amount of difference in FDM vs SLA print speed.

It’s also worth noting that DLP and LCD are significantly faster than SLA and FDM. We have a ranking of the 5 best low cost LCD 3D printers under $500.

FDM vs SLA verdict: draw.

FDM vs SLA Materials

FDM 3D printers use filaments, which are thermoplastics fed into the printer on a spool that are then melted and extruded. SLA 3D printers use liquid resins which are hardened by the UV light.

Versatility and Color Options

FDM 3D printers are compatible with many different materials, ranging from the most common like PLA and ABS to more niche or industrial options like Nylon, or carbon fiber- or wood-filled filaments.

Moreover, you can basically print in whatever color you want to with FDM. Want to print in yellow, orange or purple? No problem.

SLA 3D printers are often compatible with a versatile range of resins, such as castable and dental resins. However, you’ll struggle to find resins in colors other than black, white or grey, which creates problems for some.

fdm vs sla resins
Resins being poured into the resin tank for SLA 3D printing.

FDM vs SLA Material Strength and Part Strength

The general consensus is that FDM parts are stronger than SLA parts. They have better impact resistance, are less likely to break or degrade over time, and can be left outside.

SLA parts have a big weakness in their vulnerability to UV rays, and can therefore not be left outside in the sun or they will deteriorate rapidly.

FDM vs SLA verdict: FDM wins on material and part strength, draw in material versatility, and FDM wins on color options.

FDM vs SLA Resolution, Accuracy and Surface Finish

In all three of these areas, few FDM 3D printers can compete with the accuracy and surface finish quality offered by even a mid-range SLA printer.

This is because the FDM printing process — with its heated plastics and consecutive layers — can create warping, shrinking and general structural deformation, all of which affect the final part’s print quality. There are often small filament hairs on a print, and the underside of FDM parts is often less than presentable.

fdm vs sla printed part quality comparison
FDM vs SLA part comparison. FDM on the left, SLA on the right.

SLA 3D printed parts on the other hand have far smoother surface finishes and are almost always more accurate in terms of both resolution and accuracy. Stereolithography printer usually print with layer sizes of between 0.05mm and 0.01mm, noticeably better than most FDM 3D printers.

FDM vs SLA verdict: SLA wins.

Post-processing

With FDM if a part requires supports then these will need to be removed. Be careful to avoid damaging the part if using a scraping tool to remove the part from the print bed. Generally however, FDM parts require minimal post-processing.

With SLA, a similar process of removing supports is required, wherein the part needs to be bathed in isopropyl alcohol (wear protective gloves!) to dissolve the supports. Additionally, with SLA it is more difficult to remove a part than with FDM, as excess resin needs to be separated before the part can be removed.

FDM vs SLA verdict: the differences are inconsequential.

FDM vs SLA 3D Printer Cost & 3D Printing Cost

Costs: FDM vs SLA 3D printer purchase

Forgetting about material costs and general part replacement and just counting the nominal cost of buying an FDM or SLA 3D printer, there is no doubt that FDM 3D printers are cheaper on average.

If you’re willing to build your own FDM DIY 3D printer kit, they start from $200-300 — you can view our favorite DIY 3D printer kits here. If you want a plug-and-play FDM machine, you can pick one up for under $1,000 or go slightly higher for a very reliable consumer 3D printer. There are industrial FDM 3D printers like those by Markforged or Stratasys that sell for more, but for makers at home this is probably overkill.

ultimaker 3 fdm 3d printer vs sla
The Ultimaker 3 is still one of the best FDM 3D printers around for the price.

Although there are some low-priced SLA 3D printers, they do not come as cheap as those using FDM. Solid SLA printers such as Formlabs’ Form 3 start at $3,499, and many cost exponentially more. Some DLP 3D printers can cost less, but are not usually cheaper than $1,000 and cheap ones usually cost around $1,500.

Costs: FDM vs SLA 3D printing costs and upkeep

FDM vs SLA Material Cost

This part ties into our FDM vs SLA material comparison. As you print, you’ll use up your materials — either filament or resin — which require replenishing, at a cost. FDM filaments such as PLA and ABS are obtainable very cheaply, at around $25-30 per kilo, though more specialized filaments like HIPS or TPU cost more.

SLA resins cost far more, though the numbers again depend on the type of resin used. For a rough approximate, a liter of resin will set you back between $80-150, though castable resins can be double that.

fdm vs sla material color options
You can print in almost all colors with FDM filaments.

FDM vs SLA Printer Part Replacement Cost

FDM printers typically only need their nozzles replaced on occasion, with other parts less likely to break consistently. These are usually replaceable for under $30 and are more of an annoyance than a major setback. If you scrape your models off the print bed too aggressively you may eventually need to replace it, but this is not a regular occurrence.

SLA printers however require more regular part replacement. Resin tanks become less clear, affecting laser accuracy and costing around $60 to replace, whilst build platforms can also become damaged in a similar way to FDM printers during part removal.

FDM vs SLA cost verdict: FDM wins.

FDM vs SLA Conclusion

Overall, FDM is clearly the more accessible technology: the printers are cheaper, materials are cheaper, and parts are stronger.

However, this is offset by noticeably reduced part quality and surface finish, so your choice really depends on your priorities.

If you’re looking for an easy-to-use, cheap printer that can make solid parts without much hassle, go FDM.

If quality is important to you, and you’re printing fine details, or casting things like jewelry, go SLA.