Slicer settings for beginners: layer height, infill, supports and the first layer

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A slicer is the program that turns a 3D model into the step-by-step instructions your printer follows. It has hundreds of settings, which is overwhelming at first, but a handful decide almost everything about a beginner's results. Learn these, change one at a time, and leave the rest at the profile your printer's maker supplies.

Start from a known profile

Choose your exact printer and nozzle size in the slicer and use its default profile for your filament. Those settings were tested on your hardware. When something goes wrong, compare with the default before inventing new numbers.

Layer height: detail versus time

Layer height is how thick each slice of the print is.

Thinner layers give smoother curves and finer detail but take much longer.
Thicker layers print faster and are often stronger, with more visible lines.
A common rule of thumb is to keep layer height well under the nozzle diameter. Your default profile will usually sit in a sensible middle range.
Many slicers offer variable or adaptive layer height, using thin layers only where the model curves.

Walls, top and bottom layers

Strength mostly comes from the outer shell, not the inside.

Adding walls (perimeters) is often the most effective way to make a part stronger.
Enough top layers stop the infill pattern showing through and avoid holes on flat tops.

Infill: how solid the inside is

Infill is the internal pattern that supports the shell.

Decorative models print fine with low infill.
Functional parts need more, and more walls, rather than simply cranking infill to the maximum.
Patterns such as grid, gyroid and cubic behave differently. Gyroid is a popular all-round choice; the default pattern is fine to start with.

Supports: when the model hangs in mid-air

Each layer needs something beneath it. Overhangs steeper than about 45 degrees from vertical, and bridges across gaps, may need supports.

Orient the model first. Rotating a part so its flattest side sits on the bed often removes the need for supports completely, and makes it stronger.
Use tree or organic supports for figures and curved models; they touch the part in fewer places and peel off more cleanly.
Use support blockers or painting to add supports only where they are needed.
A small gap between support and model makes removal easier, at the cost of a slightly rougher underside.

The first layer and adhesion

Almost every beginner failure starts on the first layer. It should be slightly squashed onto the bed, with lines touching each other and no gaps, but not so close that the nozzle scrapes.

First-layer speed: slower than the rest of the print.
First-layer height: often a little thicker than normal layers to forgive a slightly uneven bed.
Brim: a flat ring of extra lines around the base that holds corners down. Useful for tall, thin or warping-prone parts.
Skirt: a loop drawn around the model before printing to prime the nozzle; it does not hold anything down.
Raft: a full platform under the part. Rarely needed on modern printers and leaves a rough base.

Levelling the bed and setting the Z offset

Heat the bed and nozzle to printing temperature first; metal expands when hot.
Clean the build surface. Fingerprints are a classic cause of parts letting go.
Run the printer's automatic levelling, or level by hand using a sheet of paper at each corner and the centre until you feel slight drag.
Print a single-layer test pattern and adjust the Z offset (the nozzle's height above the bed) while watching: too high and lines are round and separate, too low and they are thin and ragged.
Note the value that works.

A simple way to learn

Keep a notebook or a text file. Each time you change a setting, write down what you changed and what happened. After a few weeks you will understand your own printer better than any profile. Which slicer setting confused you most when you started? Ask about it, or share the one change that improved your prints, in the comments.