How to read this book

A short orientation so you know what you are looking at and what you will want nearby.

The shape of each chapter

Most chapters teach a handful of ideas, each in the same rhythm: what it is, why it matters for you, how it works in plain terms, and a few takeaways you can carry forward. The project chapters add hands-on labs: numbered steps you actually do, with a clear "you are done when..." at the end.

When two words are easy to mix up (filament and resin, a slicer and a model, PLA and PETG), you will see a box like this:

Don't be confused. A model is the digital shape of your object. A slicer is the program that chops that shape into layers and writes the instructions your printer follows. The model is the drawing; the slicer is the route planner.

Each chapter ends with a 👉 arrow pointing to the next one, so you always know where the road goes.

You do not need to buy anything to start reading

You can read this entire book with no printer in the room. Where you can follow along on a real machine, we say so. Where something needs hardware or software you might not have yet, we describe it precisely and label any sample output as illustrative so you are never misled into thinking a screenshot is a promise.

What you will eventually want on hand

Not yet, but as you move into the later parts, the full kit is small:

A 3D printer, or access to one (a library, makerspace, school, or a friend), or an online print service. Chapter 2 walks through every one of these paths.
A spool of beginner-friendly filament, most likely PLA to learn on and PETG for the squeezer itself. Chapter 3 explains why.
A free slicer program on any laptop (Chapter 5).
A free CAD tool that runs in a web browser (Chapter 8).
For the project: a real lemon, a small kitchen scale if you have one, and a willingness to make a sticky mess.

A little bit of code, and why

This is a hands-on hobby book, not a programming book, so there is very little code. Where a small script genuinely helps, you will find one: for example, estimating how much filament a print uses, or working out the dimensions of the squeezer's juicing cone. Those scripts are short, written in Python, and we show their real output. There is also one optional chapter on describing a 3D shape in code with a tool called OpenSCAD, for readers who enjoy that. You can skip it and design entirely by dragging shapes on screen instead; nothing later depends on it.

Safety, in one place

Two recurring cautions, stated once here and repeated where they matter:

Hot and moving parts. A printer's nozzle runs around 200 degrees Celsius and the bed can be hot too. The machine moves on its own. Keep fingers clear during a print and let parts cool before handling.
Food contact is not automatic. A printed object touching food raises real questions about cleaning and materials. We do not hand-wave this. Chapter 14 is devoted to it, and the project's design is shaped around it.

👉 With that, let us start at the beginning: what a 3D printer actually does.