Brims, Rafts and Skirts

None of these fixes a dirty plate or a nozzle set too high. If the first layer itself is not sticking, work through First Layer Won't Stick before adding a brim.

The four helpers

Helper	What it is	What it does for the print	What it costs
Skirt	Loops around the part, not touching it	Primes the nozzle and stabilizes flow; lets you check the first layer before the part starts. No adhesion.	A little filament
Brim	Flat first-layer lines attached to the part's edge	Bigger footprint, edges held down	Removal, a faint edge mark
Mouse ears	Small brim patches at corners only	Holds the corners that lift first	Less material and cleanup than a brim
Raft	A multi-layer platform under the whole part	A flat, well-stuck base for warp-prone materials, tiny contact areas or worn plates	Time, material, removal, a rougher bottom face

Where the settings are called what

What it controls	PrusaSlicer	OrcaSlicer	Bambu Studio	Cura
Which helper	Skirt and brim section	Brim type; Raft: Layers	Brim types (Auto, Outer brim only, Painted, No-brim and others)	Build Plate Adhesion Type: Skirt, Brim, Raft or None
Brim size	Brim width	Width	Brim Width	Brim Width or Brim Line Count
Gap between brim and part	Brim separation gap	Brim-Object Gap	Brim-Object Gap	Brim Distance
Corner-only brim	Not confirmed	Mouse Ears	Painted (brim ears)	Not confirmed

Not confirmed means we did not find the name in that slicer's documentation; the feature may still exist. Prusa's skirt and brim settings are under Print settings, Skirt and brim; Bambu Studio's brim settings are in the Other group and can be set per object.

Skirt

The skirt runs a few loops around the part before printing it. Prusa says it helps stabilize filament flow before the model prints, and lets you check first-layer adhesion and adjust live Z while it goes down. UltiMaker notes it primes the nozzle and can serve as a leveling check, but adds no adhesion to the model.

Prusa profiles typically print three skirt layers Maker spec, because a one-layer skirt is hard to get off the plate. PrusaSlicer's Draft shield option makes the skirt as tall as the tallest object, a wall that keeps drafts off warp-prone materials such as ABS and ASA (see ABS and ASA).

Brim

A brim adds first-layer area attached to the part, so the edges have more to hold on with. Bambu Lab says it is especially useful for tall, thin objects, and that materials which shrink as they cool, such as ABS, benefit because a wide enough brim keeps the edges from warping. Prusa recommends it for tall objects with small bases and for several small objects printed together.

• Width. Rule of thumb Prusa advises at least 3 mm for better adhesion. OrcaSlicer notes wider brims hold better but use more material and take longer to remove.
• Gap. A small gap between brim and part makes the brim easier to snap off. UltiMaker and OrcaSlicer both note the trade: a bigger gap removes more easily but holds less, and OrcaSlicer warns a very large gap may stop the brim touching the part at all.
• Outer, inner or both. Inner brims go inside holes. OrcaSlicer notes they are harder to remove and less effective; use outer only unless a hole's edge is lifting.
• Auto. Bambu Studio's default Auto brim works out a width per part from its shape and orientation, the filament type and print speed: tall parts with small footprints and high-shrink materials get wider brims, TPU narrower ones.

If the brim will not sit tight against the part even with the gap at zero, Bambu Lab points to elephant foot compensation as the usual cause; see Elephant's Foot.

Mouse ears

Corners lift first. Ears put brim only there. OrcaSlicer's Mouse Ears brim type places small brim patches near corners and sharp features, using less material than a full brim, and Bambu Studio lets you paint brim ears where you want them. Ears are a good first try for flat boxes and plates whose corners curl.

Raft

OrcaSlicer recommends a raft for materials prone to warping or lifting (ABS, ASA, PC, nylon), for objects with a small contact area or thin, sharp features, and for uneven or worn plates, and it says to try a brim first, since a brim is faster and uses less material. UltiMaker adds that a raft helps when the model's own bottom is uneven.

The costs are real: more time, more material, removal work, and a rougher bottom surface on the part. The raft's contact Z distance trades the same way supports do: OrcaSlicer says a larger gap releases more easily but leaves a rougher bottom. Starting point OrcaSlicer suggests 2 to 4 raft layers for most prints and more for uneven beds or strong warping.

What to choose first

1. Every print: keep a skirt, or use your printer's purge line. UltiMaker warns that turning off all adhesion features can lead to print failure.
2. Corners lifting on a flat part: mouse ears, then a full brim.
3. Tall, narrow part or small footprint: a brim of a few millimeters, and consider a wider one for fast printers.
4. Warp-prone material still lifting with a brim: a draft shield or enclosure, then a raft. See Warping.