Types of 3D printing

This page describes the two main types of 3D printing. Whether you’re just curious or want to buy a printer of your own this highlights some of the key differences.

FDM

FDM (Fused Deposition Modeling) printing is what comes to mind for most people when they think about 3D printing.

FDM printers have a flatbed that a nozzle prints (extrudes) a type of filament. The filament can be plastic, wood-based, or many other materials. It prints line by line and layer by layer.

I usually use a comparison to help people understand: imagine FDM printing as a hot glue gun. It draws/pours a layer of glue (filament) a line at a time until you eventually get the shape you want. Like a hot glue gun, the nozzle can leave behind trails of loose plastic that need to be cleaned up.

Many people like FDM printers because they are usually cheaper and have a larger printing surface than SLA printers.

Unfortunately, it’s not all upsides with FDM printers.

The biggest complaint I have with FDM printers is the build quality.

Due to the nozzle printing line by line with a hot material that cools before the next layer is added, those lines are usually very visible on prints. This isn’t always bad; if you want to make a cobblestone building, those lines can add details you would otherwise need to design yourself. If, however, you want a detailed print that looks good, those lines can change, reduce, or altogether remove details on your prints.

Another downside to FDM printers is the print time.

Printing line by line takes a long time, which might not be an issue for you. You can turn on your printer overnight and have it done in the morning. Suppose you are excited about a particular print or a making larger print. In that case, they can take multiple days, which can be very irritating.

SLA

SLA (Stereolithography) printers are another very popular type, and it was the original form of 3D printing.

SLA printers print by using UV light to harden the liquid resin. I know that doesn’t sound very clear, but stay with me.

Unlike FDM printers that melt a type of filament, SLA printers use a liquid plastic called resin (specifically, it is a photopolymer). The resin hardens (cures) when exposed to UV light.

A metal plate (build plate) is lowered into the container (vat) of resin and stops against a plastic screen (FEP). UV light then shines through the FEP in specific areas to harden the resin onto the metal plate.

Super basic version: a metal plate lowers into the resin, a UV display shines light onto the liquid, and it hardens against the metal plate. The metal plate rises slightly and lowers back against the FEP for the next layer.

The most significant upside to SLA printers is the detail of prints. Unlike FDM printers, where the material melts and resolidifies before the next layer is added, the next layer for SLA printers is immediately afterwards. You aren’t going to get those print lines unless something in your print settings is wrong.

Another huge upside to SLA is the print time. Because UV light is shining onto the resin, it will take the same amount of time to print the entire surface of the build plate as doing a tiny portion. This means you can print multiple objects with no added build time. Short and wide prints will only take as long as other short prints. Do you need to make ten goblins for your upcoming TTRPG session? Congrats! With an SLA printer, it’ll take the same time as printing 1.

As always, there are some downsides, and honestly, there are some big ones.

Liquid plastic isn’t good for you. That seems obvious, I know, but if you’re working with it, you need to take some precautions.

Nitrile gloves (or other nonpowdered gloves) must be worn when handling uncured (liquid) resin. If it touches your skin, it’s not the end of the world but get ready for it to be itchy and irritated.
Eye protection, just like your science teacher always told you, “When you’re dealing with chemicals, ensure you have eye protection.” If you’re taking your prints off your build plate, some resin can splash into your eyes. Remember that itchy, irritated skin I talked about? Yeah, it’s much more unpleasant if you get it in your eye.
Fumes. Plastic can be smelly, especially when it’s a liquid. Breathing the resin fumes (like most fumes) can harm your health. I recommend putting an SLA printer somewhere with good ventilation and air purifiers. It’ll also be very smelly. You can buy low-odour (often plant-based) resin. These still have the classic resin smell, but in my experience, it hasn’t been quite as bad.

Small build volume

SLA printers have a smaller build volume than FDM printers. It will be difficult and expensive if you want to build larger items such as terrain or other objects.

Material cost.

Resin is (on average) more expensive than filament.
Not only that, but you’ll also need to get Isopropyl alcohol (IPA) of a pretty high percentage. IPA is used to remove uncured resin from your finished prints. Water (unless you use water washable resin) won’t do the job, and putting uncured resin down the drain is bad for the environment. Some people buy a wash machine filled with IPA that cleans their prints.
Curing station. If you’re looking at this website, you probably live in Edmonton. You’ve probably noticed this, but we don’t get all that much sun, and when we do, it doesn’t have a very high UV index. This means that to finish curing your prints once they’re done, you’ll need to put them into a curing machine ($40-$200+)

Sunlight will cure the resin.

Are you thinking about putting your SLA printer in a brightly sunlit room? Bad news, that will probably wreck your prints and waste a lot of that expensive resin. You’ll need a room that can be almost (if not totally) dark. I use my closet.

That seemed like a lot of negatives for only faster, better prints. So why is SLA still so popular? Because of the high level of detail, smooth finish, and water-tight exterior. For these reasons, SLA is not only used by hobbyists; it is also used in the medical industry.

FDM or SLA?

So, you’ve made it this far and now you’re asking “So? Which is better?” Unsurprisingly, the answer is “It depends.” That’s very unsatisfying so here are some things to make your decision easier.

What do you want to use it for?

Are you a hobbyist who wants to try out 3D printing or don’t want to break the bank on something you don’t know if you like? Super detailed prints not that important to you? Want large prints such as terrain for TTRPGs

I’d recommend picking an FDM printer. Generally cheaper, and less hassle to deal with, not to mention you won’t need an unusable, smelly room to run it. FDM would be a great choice.
The go-to recommendation for most is a Creality Ender 3. Ranging from $230-$300 it’s a great budget printer that will get the job done.
If you want a larger build area than the Ender 3, the Creality CR-10 family (CR-10, CR-10 Pro, CR-10 V2, V3) is also an excellent choice.

Do you want higher quality prints for a bit more work and cost? Is the fast printing time drawing your eye?

My personal introduction to 3D printing was an SLA printer. The build quality is outstanding and was exactly what I wanted. I had some room in my closet and figured I like things to look good, so I gave it a shot.
The extra hassle of needing nitrile gloves, and washing the prints after they’re done to get the uncured resin off is definitely something to keep in mind. That said, if I were to choose my first printer again I would stick with SLA.
The detail on the prints is outstanding and I still can’t get over it. Explaining how it works is also very fun (clearly as I rambled on for quite a while) and maybe some of you will agree with me on that and get to experience it yourself.
The Anycubic Photon family is often a recommended SLA printer $230-$800+
Elegoo Mars $280+ or Saturn $600+ are also both good choices

There’s no right or wrong answer here. What was the right choice for me will not be the right choice for everyone. Hopefully, this guide will help make your choice a bit easier..

If you want another opinion on any of anything I’ve said in this guide Form Labs has a great description and videos