WHEN TO USE A BRIM, SKIRT, OR RAFT

Skirt: an outline of perimeter loops printed near the model but not touching it. Purpose: prime the nozzle and confirm extrusion is clean before the model starts. Doesn't help adhesion. Brim: flat loops printed *attached* to the model's first layer, extending outward. Purpose: increase bonded surface area to prevent warping and corner lifting. Removes with flush cutters after printing. Raft: a multi-layer base printed *under* the model. Purpose: provide a fresh smooth surface when the build plate is unreliable, or compensate for severe warping on technical filaments. Adds significant print time and material.

Use a skirt when: every print, basically. 1-2 outline loops at print start cost almost nothing and confirm the nozzle is priming cleanly. Default to skirt = 1-2 loops. Use a brim when: large flat parts on PLA/PETG (over 100 mm wide), any ABS or ASA print regardless of size, prints with thin tall features that lift off easily, prints on bare glass without adhesion aid. Use a raft when: the build plate has visible scratches or low spots that ruin first layers, you're printing flexible filament (TPU) on a surface it doesn't grip, you need a perfectly flat bottom but the bed has texture, or you're printing very small parts with tiny first-layer footprints. Don't use a brim when: first-layer adhesion is already reliable (PLA on textured PEI for normal-size parts), or the brim would mark the visible bottom of a display piece. Don't use a raft when: a brim would solve the same problem (95% of the time it would). Rafts waste 10-30 minutes of print time and 5-15 g of filament.

Setting up a skirt: - All slicers: Print Settings - Skirt - 1-2 loops, 5-10 mm distance from model. Skirt height: 1 layer. - Adjust skirt distance to 0 mm if you want it to act as a partial brim for very small parts. Setting up a brim: - Cura: Build Plate Adhesion Type - Brim. Brim Width: 5-10 mm. For ABS/ASA: 10-15 mm. - PrusaSlicer: Skirt and brim - Brim type - Outer brim only. Brim width: 5-10 mm. - OrcaSlicer / Bambu Studio: Brim type - Outer brim. Brim width: 5-10 mm. Brim object gap: 0 mm (brim attached to model). - For tall thin features that need extra hold: Brim type - Outer and inner (Cura: 'Brim Outside Only' off). Setting up a raft: - Cura: Build Plate Adhesion Type - Raft. Raft Air Gap: 0.2-0.3 mm (gap between top of raft and model). Raft Top Layers: 2. - PrusaSlicer: First layer extrusion type - Raft. Raft layers: 2-3. - OrcaSlicer / Bambu Studio: Raft layers: 2-3. Raft contact distance: 0.1-0.15 mm. - For flexible filaments specifically: increase raft air gap to 0.3-0.4 mm or supports won't release. Removal tips: - Brim: flush cutters along the model edge, sand any residue. - Raft: gently flex from one corner; should peel cleanly if air gap is right.

Using a raft when a brim would work. Wastes 5-15 g of filament and 10-30 minutes per print. No brim on ABS/ASA prints. ABS warps without a 10+ mm brim almost regardless of bed temp. Brim too narrow for the print. A 3 mm brim on a 200 mm wide ABS part won't hold. Scale brim width to part width. Skirt set to 0 loops. No nozzle priming = first line of model is patchy. Always use 1-2 skirt loops. Forgetting to remove the brim before measuring. Dimensional checks include the brim - looks like the part is bigger than designed.

If you're using a brim because of warping, address the underlying cause too - see warping-lifting. If your raft won't release cleanly, the air gap is too small - similar to the support-scarring guide's interface settings.