3D Printing Basics
The fundamentals of desktop FDM 3D printing — how it works, the parts of a printer, the model-to-print workflow, and the vocabulary the rest of this section assumes.
What is FDM?
Fused Deposition Modelling (FDM) — also called Fused Filament Fabrication (FFF) — builds an object by melting a plastic filament and depositing it in thin layers. A motor pushes a 1.75 mm filament string into a heated nozzle, the melted plastic is laid down along a path, and the print head moves up one layer height to draw the next slice. Stack a few hundred layers and you have a physical part.
It is the most common and affordable form of consumer 3D printing. The main alternative, resin (SLA/MSLA), cures liquid photopolymer with UV light and gives far finer detail, at the cost of messier, more toxic handling.
| FDM (filament) | Resin (SLA/MSLA) | |
|---|---|---|
| Detail | Good; visible layer lines | Excellent; very fine |
| Strength | Strong, functional parts | Often brittle |
| Materials | Huge range (see Filaments) | Photopolymer resins |
| Mess / safety | Low | Sticky, toxic, needs gloves + ventilation |
| Best for | Functional parts, prototypes, large prints | Miniatures, jewellery, fine detail |
The rest of this section is about FDM.
Anatomy of a printer
graph TD
A[Spool of filament] --> B[Extruder / drive gear]
B --> C[Hotend: heater + nozzle]
C --> D[Molten plastic on the bed]
D --> E[Heated build plate]
F[Motion system: X / Y / Z] --> C
G[Mainboard + firmware] --> B
G --> C
G --> E
G --> F| Part | What it does |
|---|---|
| Extruder | Motor + gear that grips and pushes filament. Direct-drive mounts it on the print head (better for flexibles); Bowden mounts it on the frame and feeds through a tube (lighter head, faster). |
| Hotend | Melts the filament. Includes the heater block, thermistor, heat break, and nozzle. An all-metal hotend is needed for high-temp materials (> ~240 °C). |
| Nozzle | The tip the plastic exits. Common sizes 0.4 mm (default), 0.2 mm (detail), 0.6–0.8 mm (fast/strong). Brass is standard; hardened steel for abrasive filament. |
| Build plate / bed | The heated surface the print sticks to. Surfaces include PEI (spring steel), glass, and textured sheets. |
| Motion system | Moves the head in X/Y/Z. Cartesian/bed-slinger (bed moves on Y), CoreXY (head moves in X/Y, bed only drops — faster, more rigid), or delta. |
| Part-cooling fan | Blows air on the freshly laid plastic so it solidifies. Critical for PLA/PETG overhangs; turned down/off for ABS/ASA/nylon. |
| Mainboard + firmware | Runs the printer (Marlin, Klipper, RRF). Klipper offloads motion planning to a Raspberry Pi/host for higher speeds and input shaping. |
The workflow
graph LR
A[3D model<br/>.stl / .3mf / .step] --> B[Slicer]
B --> C[G-code / .3mf]
C --> D[Printer]
D --> E[Post-processing]- Get a model. Download one (Printables, Thingiverse, MakerWorld, Thangs) or design your own in CAD (Fusion 360, Onshape, FreeCAD, Tinkercad, Blender for organic shapes).
- Slice it. A slicer converts the 3D model into G-code — the layer-by-layer toolpath and machine instructions. Common slicers: OrcaSlicer (popular, feature-rich), PrusaSlicer, Bambu Studio, Cura. Here you set layer height, infill, supports, temperatures, and speed (see Print Settings).
- Print. Send the G-code via SD card/USB, or over the network with OctoPrint, Klipper's web interfaces (Mainsail/Fluidd), or the vendor's cloud/app.
- Post-process. Remove supports, peel off the brim, sand, glue multi-part prints, vapour-smooth (acetone for ABS, IPA for PVB), or paint.
Key terms
| Term | Meaning |
|---|---|
| Layer height | Thickness of each layer (e.g. 0.2 mm). Smaller = finer detail, more layers, slower. |
| Infill | The internal lattice. Given as a percentage (10–20 % typical) and a pattern (gyroid, grid, honeycomb). 0 % is hollow, 100 % is solid. |
| Perimeters / walls / shells | The outer loops of each layer. More walls add strength more efficiently than more infill. |
| Top / bottom layers | Solid layers that cap the infill. |
| Adhesion helpers | Skirt (priming loop), brim (flat collar for grip), raft (full base layer under the part). |
| Supports | Scaffolding printed under overhangs steeper than ~45–60°, removed afterwards. |
| Bridging | Spanning a gap in mid-air between two points without support. |
| Retraction | Pulling filament back to stop oozing during travel moves. Key to fighting stringing. |
| First layer | The most important layer — poor bed adhesion or a bad first layer ruins the whole print. |
| Elephant's foot | First-layer bulge from heat + weight; reduced with bed-temp and Z-offset tuning. |
| Slicer | Software that turns a model into printer instructions (G-code). |
| G-code | The text instructions a printer executes (move here, extrude this much, set this temperature). |
Bed adhesion & the first layer
Most failed prints fail on layer one. Getting a good first layer down:
- Level the bed / set Z-offset. The nozzle should be exactly the right height — too high and lines don't stick; too low and they smear. Many modern printers do this automatically with a probe (auto bed levelling / mesh levelling).
- Clean the plate. Grease from fingerprints is the #1 adhesion killer. Wipe with isopropyl alcohol; wash textured/PEI sheets with dish soap occasionally.
- Right bed temperature for the material (see Filaments).
- Adhesion helpers — a brim for tall/small-footprint parts; glue stick as adhesion (ABS/PC/nylon) or as a release layer (PETG on PEI/glass).
Dial in the first layer, once
Print a first-layer test or a bed-level pattern when you set up a printer or swap surfaces, and note the Z-offset per filament. It saves far more time than it costs. See Print Settings and Troubleshooting.
What you need to start
- A printer. Modern auto-levelling machines (Bambu Lab, Prusa, Creality K-series, Sovol) remove most of the old pain of manual tramming and are the easiest entry.
- PLA filament to learn on — cheap and forgiving.
- A slicer (OrcaSlicer is a great free default).
- Basic tools: a scraper/spatula, flush cutters, a glue stick or IPA, and calipers for checking dimensions.