FDM 3D Printing Explained | Extrusionary Designs Blog

New to 3D printing? This plain-English guide explains exactly what FDM 3D printing is, how the process works layer by layer, and what kinds of things you can actually make with it.

FDM 3D printing is the most widely used form of 3D printing in the world — and for good reason. It's accessible, versatile, and capable of producing everything from decorative trinkets to serious functional engineering parts. If you've never ordered a custom print before and aren't sure what the process even looks like, this guide is for you.

What Does FDM Actually Stand For?

FDM stands for Fused Deposition Modelling. You might also see it called FFF — Fused Filament Fabrication — which means the same thing. Both names describe the same core process: melting a strand of plastic and depositing it precisely, layer by layer, to build up a three-dimensional object from the ground up.

Think of it like a very precise, very controlled hot glue gun — one that follows an exact digital blueprint and never misses.

How Does FDM 3D Printing Work?

The basic process looks like this:

Start with a 3D file — the printer needs a digital model, usually an STL or 3MF file. This can be something you've designed in CAD software, downloaded from a model library, or created from a 3D scan.
Slice the model — slicing software (like Cura, PrusaSlicer, or Bambu Studio) converts that 3D file into a set of instructions for the printer, slicing the model into hundreds or thousands of horizontal layers and calculating exactly how the nozzle needs to move to recreate each one.
Heat and extrude — the printer feeds a spool of plastic filament into a heated extruder, which melts it and pushes it out through a small nozzle (typically 0.4mm in diameter), depositing thin lines of molten plastic in precise patterns over a build plate.
Build layer by layer — each layer cools and solidifies almost instantly. The print bed (or the nozzle) moves down fractionally, and the next layer is deposited on top of the previous one. This repeats hundreds or thousands of times until the object is complete.
Remove and post-process — once the print is done, the part is removed from the bed. Depending on the design, support structures may need to be removed, and the surface can be sanded, painted, or finished as needed.

What Materials Can FDM Printers Use?

One of the biggest strengths of FDM printing is the range of materials available. Different filaments have very different properties:

PLA (Polylactic Acid)

The most common filament. Easy to print, comes in every colour imaginable, produces great detail and surface finish. It's biodegradable, slightly brittle under stress, and not great for high-heat environments — but for decorative parts, enclosures, props, and most everyday applications, PLA is the go-to.

PETG (Polyethylene Terephthalate Glycol)

Tougher and more impact-resistant than PLA, with better heat tolerance. Great for functional parts that need to handle a bit more stress. Slightly glossier surface finish. We use PETG a lot for parts that need to actually do something, not just look good.

TPU (Thermoplastic Polyurethane)

Flexible, rubber-like filament. Perfect for anything that needs to flex, grip, or absorb impact — phone cases, seals, gaskets, grips. Trickier to print than PLA but the results are great when you need that rubbery quality.

ASA & ABS

Higher-temperature materials suited for outdoor or under-bonnet applications. UV resistant (ASA especially) and more heat-tolerant than PLA or PETG. Harder to print well, but worth it for the right applications.

Not sure which material you need? When you place a custom order with us, just describe what the part needs to do and we'll recommend the right filament. That's part of the service.

What Can You Actually Make with FDM 3D Printing?

This is the question most people start with — and the honest answer is: a lot. Here's a rough breakdown of the kinds of things FDM printing is genuinely good for:

Functional parts and brackets — mounts, clips, adapters, spacers, enclosures
Replacement components — parts that are discontinued, hard to source, or prohibitively expensive from the OEM
Prototypes — test a design in your hands before committing to an expensive manufacturing run
Props and costume pieces — armour, accessories, weapons, masks — sized and finished how you need them
Toys and hobby items — figurines, terrain, miniatures, RC parts
Custom products — anything you can dream up that doesn't exist off a shelf

The main limitation of FDM is that it's not suited for parts that need extreme precision tolerances, very thin walls, or optical-quality surface finishes right off the printer. For those applications, resin printing or CNC machining are usually better options. But for the vast majority of real-world use cases, FDM is exactly what's needed.

What About Large Format FDM?

Standard desktop FDM printers have a build volume of roughly 220mm x 220mm x 250mm — which is plenty for most parts. But some projects need more. Large format FDM printers can handle significantly bigger builds, which opens up possibilities like full motorcycle bodywork panels, large props and set pieces, big enclosures, and parts that would otherwise need to be split and joined.

At Extrusionary Designs, we run both standard and large format FDM setups, so if your project is on the bigger side, we've got you covered.

Frequently Asked Questions

How long does a 3D print take?

It depends heavily on size, complexity, and quality settings. A small part might print in 1–3 hours. A large or detailed print can run overnight — or over multiple days for very large objects. We'll always give you an estimated timeframe when you get in touch.

Do I need to provide a 3D file?

Not necessarily. If you have a file, great — we can work with STL, 3MF, STEP, and most other common formats. If you don't have a file, we offer CAD design services and can design your part from a sketch, photo, or description. We also offer 3D scanning for existing objects you need replicated or modified.

Can 3D printed parts be painted or finished?

Yes. FDM prints can be sanded, primed, painted, and sealed like any other plastic part. The layer lines visible on raw prints largely disappear with light sanding and primer, leaving a smooth paintable surface.

What's the difference between FDM and resin printing?

FDM (this guide) builds parts by melting and depositing plastic filament. Resin printing uses UV light to cure liquid resin, producing much finer detail and smoother surfaces — but parts tend to be more brittle, build volumes are smaller, and the process is messier. We use FDM because it's more practical for functional parts, larger prints, and the kinds of custom work our customers need.

Ready to Get Something Printed?

Whether you've got a file ready to go or just an idea in your head, we're here to help make it physical. Get in touch and tell us what you're working on — we'll take it from there.

FDM 3D Printing Explained: What It Is, How It Works & What You Can Make