3D PrintingBuild your first model in Tinkercad

Introduction to 3D Printing and Modelling

By Admin, 15/09/2026 · 6 min read

How an FDM 3D printer builds an object layer by layer, from a design file to a finished print. Part 1 of a four-part series on 3D printing and Tinkercad.

3D printing

How does a 3D printer actually work?

A 3D printer builds a solid object by adding material one thin layer at a time, under the control of a computer. This way of building is called additive manufacturing, because the printer adds material instead of cutting it away.

Fix It Today's printers, the Bambu Lab X1 Carbon and the H2D, both build objects using a method called FDM. FDM is short for Fused Deposition Modelling. An FDM printer builds objects out of melted plastic, one layer at a time.

From a file to a finished object

Design, slice, print

Four steps turn a shape on a screen into an object you can hold.

1

Every 3D print starts as a 3D model. A 3D model is a file that records the exact shape of an object in three dimensions. Someone designs this file on a computer, using software made for 3D modelling. You'll usually see this kind of file end in .stl or .3mf.

2

A program called a slicer reads the 3D model next. The slicer cuts the shape into many thin, flat layers, a bit like slicing a loaf of bread. Each layer is one horizontal slice of the finished object.

3

The slicer writes exact instructions for every layer. These instructions tell the printer how far to move and how much melted plastic to push out at each point. The slicer saves everything in a file called G-code, a long list of precise moves for the printer to follow.

4

The printer reads the G-code file from the first line to the last. It prints one full layer. Then it moves up a tiny amount and prints the next layer directly on top. It repeats this many times until the object is finished.

The parts of an FDM printer

What each part does

A real Bambu Lab X1 Carbon, with its AMS filament unit on top.

A Bambu Lab X1 Carbon 3D printer with its AMS filament unit on top

Nozzle (hot end)The nozzle heats up until it's hot enough to melt solid filament into liquid plastic. It then pushes the melted plastic out through a tiny hole, similar to a hot glue gun.

Print bed (build plate)The print bed is the flat surface the printer builds on, and on many printers it heats up too. That warmth helps the first layer stick down firmly, so you'll usually need to wait for it to cool before removing a finished print.

Filament spoolFilament is a long, thin thread of plastic, roughly as thick as spaghetti, wound around a spool like thread on a sewing reel. A motor inside the printer pulls filament off the spool and feeds it into the nozzle.

GantryThe gantry is the frame that carries the nozzle around while it prints, sliding it left-right and front-back, the X and Y directions, above the bed. On the X1 Carbon and the H2D, the build plate itself moves down a tiny amount after every layer, which is what creates the third direction, Z. Between the gantry's X and Y motion and the bed's Z motion, the nozzle can reach any point in any layer.

AMS (Automatic Material System)The AMS is a unit that holds several spools of filament and switches between them on its own, so the printer doesn't need someone to change filament by hand mid-print. This lets one object print in several colours or materials, and both the X1 Carbon and the H2D can use one.

How the layers build up

Melted plastic, one layer at a time

Nozzle depositing a bead onto the previous layers of a printed part — The nozzle deposits a bead of melted plastic onto the layer underneath it.

1

Melted plastic leaves the nozzle as a thin string. It cools and hardens quickly once it's out in the air. This fast cooling is what lets the printer place one layer directly on top of the last one.

2

Each new layer has to bond to the layer underneath it. If a layer doesn't stick properly, the object can crack or come apart later, sometimes even while it's still printing.

3

A shape with nothing underneath it is hard for a printer to build. This kind of shape is often called an overhang. Melted plastic has nowhere to land if it's pushed out into empty air, so it sags or drips instead of forming a clean layer. Printers often get around this by adding thin support structures underneath the overhang, which get removed once the print is done.

What the object is made of

Filament and PLA

Filament comes in several types of plastic, and each type behaves a little differently when it's heated. PLA is a type of plastic filament used by many school 3D printers, because it melts at a temperature these printers can reach easily and doesn't warp much as it cools. It's made partly from plant starch, such as corn, while many other printing plastics come from crude oil.

Ask an adult first

The nozzle gets hot enough to melt plastic, so it can burn skin if it's touched by accident. Other parts, like the heated print bed, can also stay warm for a while after a print finishes. Because of this, kids should only use a 3D printer with an adult close by, especially when opening the printer or handling a print that might still be warm.

Watch it happen

A short video

Video: How a filament printer works

Where to go next

This is a series

This page covers what a 3D printer is actually doing. The rest of the series is where the hands-on work happens: designing a first model in Tinkercad, a full tour of every Tinkercad tool, and a second, more advanced project that puts the whole toolbox to work. Each page links to the next one further down.

Once a design is exported from Tinkercad, a program called a slicer turns it into instructions a printer can follow. Bambu Studio is the slicer used with Fix It Today printers, and it has its own full guide.

Your first model: a keychain in Tinkercad
Using Bambu Studio: models, slicing and printing
3D printing theory and material properties
Choosing filament for 3D printing
Bambu Studio settings that matter most