1.1 How a 3D printer works, and the words for it
Module 1 · Part 1: Understand the machines · Lesson 1 of 14 · about 6 min
These are filament printers, also called FDM printers (fused deposition modelling). The idea fits in one sentence: a small nozzle draws your object in melted plastic, one thin flat layer at a time, and each layer fuses to the one below it as it cools.
Labelled diagram of the filament path: from a spool in the AMS 2 Pro, through the PTFE tube to the print head, between the extruder gears, past the filament cutter and down through the hotend to the nozzle, which lays the first layers on the build plate on the heatbed. An inset shows a hotend with its cool and heated sections
From plastic string to finished part
The plastic comes as filament: a 1.75 mm string wound on a spool.
An extruder, a pair of motor-driven gears, grips the filament and pushes it forward.
The filament enters the hotend, which heats and melts it. Only its lower part gets hot: the top is kept cool, so the filament does not soften before it gets there. PLA is printed at around 210 °C.
The melted plastic comes out of the nozzle, a metal tip with a 0.4 mm hole on these machines. That is roughly how wide every line in your print will be.
The nozzle moves over the build plate and draws one layer.
The heatbed carrying the plate moves down by one layer height, usually 0.2 mm, and the nozzle draws the next layer on top.
A few hours later you have an object made of a few hundred stacked layers.
Close-up of the nozzle laying down a layer on a white part, with the layer lines visible on its side
How the printer knows what to draw
It doesn't, until you tell it. A 3D model file, usually an .stl or .3mf, only describes the shape of an object. The printer can't print from that directly.
So you first open the model in a slicer: a program on a computer that turns the model into step-by-step instructions for the printer. It cuts the model into hundreds of thin horizontal slices, which is where the name comes from. Then it works out how to draw each slice: where the nozzle moves, how fast, how much plastic to push out and how hot everything should be. If you turn supports on, it also adds them where the model needs them. The result is a print file that you send to the printer.
Our slicer is Bambu Studio, made by the same company as the printers. It is already set up on the wall computer in the printing room and on the workstations in the big room (1.10 Slicing in Bambu Studio).
The slicer is where you make all the decisions. The printer just does what it is told.
Words this course uses
Word | What it means |
|---|---|
Filament | The plastic string you print with. Always 1.75 mm here. |
Spool | The roll the filament is wound on. |
Extruder | The motor-driven gears that push filament into the hotend. |
Hotend | The heated part that melts the filament. |
Nozzle | The tip the plastic comes out of. Ours are 0.4 mm. |
Build plate | The removable, flexible steel sheet your print sticks to. |
Heatbed | The heated platform the build plate sits on, held by magnets. The heat helps the first layer stick and keeps the print from warping. |
Layer height | How thick each layer is. Thinner layers give finer detail and a longer print. |
Walls (wall loops) | The solid outline of each layer. This is where most of a part's strength comes from. |
Infill | The sparse internal lattice that fills the inside of the part. |
Top/bottom shells | The solid layers that close the part at the top and bottom. |
Overhang | A part of the model that leans out over nothing. |
Supports | Temporary scaffolding under overhangs, explained below. |
Purge | Plastic the printer wastes on purpose to clean out the nozzle. The waste is often called poop in the 3D printing community. |
Purge line | The short squiggle printed next to your part at the start. |
Prime tower | A small throwaway tower printed next to your part when the colour changes. |
AMS | The Automatic Material System that feeds filament to the printer. 1.4 Meet the AMS. |
PTFE tube | The white tube the filament travels through. |
Coupler | The push-in connector that holds the end of a PTFE tube in place. |
Slicer | The program that turns a 3D model into instructions for the printer. Ours is Bambu Studio. |
Spaghetti | What a failed print looks like. You will recognise it when you see it. |
What supports are for
Melted plastic needs something underneath it. The nozzle cannot print onto thin air.
So when part of a model leans out too far, the slicer adds supports: a thin temporary scaffold underneath, which you break off afterwards. Think of an outstretched arm, the underside of an arch, or a wide flat ceiling.
About 45–50° from vertical is the limit. A wall that leans out less than that still has enough of the layer below to rest on. If it leans further, each layer's edge hangs over nothing and sags.
Short gaps often need nothing. The printer can stretch plastic across a narrow gap ("bridging"). That is why a small hole in a wall usually prints fine and a wide flat ceiling does not.
Try turning the model before adding supports. Rotating it can remove the need for supports altogether, and supports always cost plastic, time and surface quality. Turning the model also changes which way the layers run, though, and a part is weakest along its layer lines. Don't lay a part down so that the load will pull the layers apart.
Supports leave marks. The surface is rougher wherever a support touched the part. You can choose which face gets the marks by choosing how the model is turned.
Supports are meant to break off, by hand or with pliers, once the part has cooled. PLA supports on a PLA part can be stubborn. That is normal. If you think you are about to snap the part, stop and ask in Slack.
There is a better way, in Module 2. Special support material is designed to come off cleanly. Printing it is the main job of the X2D's second nozzle (1.3 The printers).
If you are unsure, turn support on when you slice. The slicer only adds them where it thinks they are needed. Unnecessary supports are a nuisance. Missing supports mean a failed print.
⬅️ Previous | 📚 Module | Next ➡️ |
|---|---|---|