Slicer Basics

A slicer is the software that converts your 3D model into instructions the printer can follow. It sits between the model file and the print.

The mental model

Your 3D model is a description of a shape — a mesh of triangles in 3D space. The printer can’t use that directly. The slicer slices the model into horizontal layers and generates a path for the nozzle to follow on each layer, along with temperature commands, fan speed commands, and retraction moves. The output is a file called G-code.

Think of the slicer as a compiler: source code goes in, machine instructions come out. You configure it; it translates.

Two slicers worth knowing

PrusaSlicer — free, open-source, works with any FDM printer. Strong default profiles, excellent layer preview, good documentation. This is the reference slicer for this site.

Bambu Studio — free, based on PrusaSlicer. Best choice if you have a Bambu Lab printer. The UI is slightly cleaner; the feature set is similar.

Both are free. Download whichever matches your hardware.

The basic workflow

Import your model — drag an STL or 3MF file into the slicer window, or use File → Import.
Choose your printer profile — select your exact printer model from the list. This sets bed size, max temperatures, and other hardware limits.
Set the material — select PLA, PETG, or ABS. The slicer adjusts temperatures automatically.
Configure the five key settings (see below).
Preview the layers — click the layer preview slider and scrub through the layers. Look for obvious gaps, missing supports, or weird toolpaths.
Export G-code — save to SD card, USB, or send directly to the printer if you have a network connection.

The five settings you’ll actually touch

1. Layer height

Controls how thick each printed layer is. Thinner layers = smoother surface, longer print time. Thicker layers = faster print, more visible layer lines.

0.1 mm — fine detail, slow. Good for figurines.
0.2 mm — the default. Right for almost everything.
0.3 mm — fast, coarser. Good for functional parts where appearance doesn’t matter.

Start at 0.2 mm and only go lower if you have a specific reason.

2. Infill percentage

How solid the inside of the print is. 0% = hollow shell. 100% = solid plastic.

15% — default for decorative prints. Plenty strong for anything non-functional.
40% — functional parts that need strength.
80%+ — rarely needed; the perimeter walls provide most of a part’s strength anyway.

3. Supports

Supports are automatically generated scaffolding for overhanging geometry. Any part of the model that overhangs more than about 45° from vertical without something below it will sag or fail without support.

Turn supports on when: the model has overhangs greater than 45°, bridges longer than ~80 mm, or the slicer preview shows unsupported sections.

Use tree supports when available — they touch the model at fewer points and leave a cleaner surface.

4. Print speed

How fast the nozzle moves. Faster = less time, more risk of errors (layer shifts, vibration artefacts, under-extrusion on corners).

Start at 50 mm/s for everything and only increase after you’ve had a few successful prints. The stock profiles are usually safe.

5. Brim

A brim is a flat ring of extra material printed around the base of your model, attached at the bottom layer. It increases the footprint that contacts the bed, improving adhesion.

Use a brim when: you’re printing something tall and thin, something with a small footprint, or ABS/PETG that tends to warp.

Width: 5–10 mm is usually enough.

What can go wrong

Using the wrong printer profile — a profile for a 0.6 mm nozzle will generate paths that are too wide for a 0.4 mm nozzle. Double-check the profile every session.
Not previewing the layers — the layer preview catches 90% of obvious problems before you start a 10-hour print. Always scrub through it.
Turning supports off when the model needs them — the slicer will warn you if overhangs are steep, but it won’t stop you. Look at the model in the preview and identify any sections that are floating in mid-air.
Cranking speed up to save time — a 3-hour print at 100 mm/s that fails halfway costs more time than a 4-hour print at 50 mm/s that succeeds. Speed up gradually, only after you’ve confirmed quality at lower speeds.