Brim, Skirt and First-Layer Adhesion Aids Explained

Brim and skirt look similar — extra plastic printed around the model before or alongside it — but they solve completely different problems, and reaching for the wrong one wastes filament without fixing anything.

Brim: more first-layer contact area, on purpose

A brim is extra material printed flush against the model's base, widening its effective footprint on the plate. More contact area means more adhesion force holding the part down, which is exactly what a shrinking, warping-prone material (ABS, ASA, PC, PA) needs at the corners where accumulated shrinkage tries hardest to lift the part. Bambu Studio's default brim width is 5 mm, with a small gap (0.1 mm) between the innermost brim line and the model so the brim snaps off cleanly instead of fusing to the part.

Use a wider brim (8–10 mm) for ABS/ASA/PC/PA, especially on parts with sharp corners or a large flat footprint — see the ABS/ASA warping guide for the full playbook, of which brim is one piece.

Skip the brim (or keep it minimal) for PLA and small parts — the extra adhesion usually isn't needed, and it's cleanup time and filament spent for no real benefit.

Skirt: a priming and verification loop, not an adhesion aid

A skirt is a perimeter printed a short distance away from the model, not touching it. Its job is entirely different from a brim's: it primes the nozzle with fresh, evenly-flowing filament before the real print starts, and it gives a visual check that the first layer looks right (even squish, no gaps) before the printer commits to the actual part. A skirt printed thin and patchy is an early warning that the first layer overall will have problems — catching that in the first 30 seconds is the whole point.

Why there's no "raft" option in Bambu Studio

Rafts — a full sacrificial base layer printed under the entire model, common in older Bowden-slicer workflows for very poor adhesion or difficult materials — aren't part of Bambu Studio's adhesion toolkit the way brim and skirt are. In practice, a properly matched plate, plate temperature and a brim solve the adhesion problems a raft used to paper over; if a part still won't stay down after those three are right, the underlying problem is usually warping (a thermal/cooling issue, see the warping guide) rather than something a raft-style sacrificial layer would fix.

Quick decision guide

Frequently asked questions

When should I use a brim instead of a skirt in Bambu Studio?

Use a brim when the part itself might lift: it prints flush against the model’s base and widens its footprint, which shrinking materials like ABS, ASA, PC and PA need at the corners. Use a skirt when you only want to prime the nozzle and visually verify the first layer before the print commits — it doesn’t touch the model and adds no adhesion.

How wide should a brim be for ABS or ASA?

Use a wider brim of 8–10 mm for ABS, ASA, PC and PA, especially on parts with sharp corners or a large flat footprint. Bambu Studio’s default brim width is 5 mm, with a small 0.1 mm gap between the innermost brim line and the model so the brim snaps off cleanly. For PLA and small parts, skip the brim or keep it minimal.

Why is there no raft option in Bambu Studio?

Because a properly matched build plate, the right plate temperature and a brim solve the adhesion problems a raft used to paper over in older Bowden-era slicers. If a part still won’t stay down after those three are right, the underlying problem is usually warping — a thermal and cooling issue — rather than something a raft-style sacrificial layer would fix.

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