Brim

The slicer extrudes the brim as a series of concentric loops attached directly to the outer perimeter of the first layer. Common widths are 5–10mm. After the print finishes, you peel or cut the brim off — it leaves a small witness mark you can smooth with a knife or sandpaper.

Brims fix the most common FDM print failure: a tall, narrow part warping at the corners and detaching from the bed mid-print. Adding a brim is cheaper than tuning bed adhesion settings, and it works for ABS, PETG, and nylon prints that would otherwise curl off the build plate.

For visual parts on a perfectly tuned bed, skip the brim — it adds post-processing time and leaves a small ridge at the base. For functional parts where adhesion failure would waste hours, add a 5mm brim by default.

Brim is not the same as raft. A brim is a single-layer skirt attached to the first layer of the part. A raft is a thick, multi-layer base printed underneath the part with the part printed on top. Brim is faster and uses less material; rafts give better adhesion on a marginal bed.

Skirt is yet another thing — a few loops printed around the part but not touching it. Skirts prime the nozzle and confirm bed leveling before the part starts.