Brims, Rafts, and Skirts

Skirts, brims, and rafts are first-layer add-ons that solve different startup problems. Use a skirt to confirm the nozzle is primed and your first layer is behaving, a brim to add real adhesion area to fight edge lift and stabilize small footprints, and a raft only when you need a sacrificial base to brute-force adhesion (accepting extra time and a worse bottom surface).

TL;DR

Use a skirt to verify first-layer flow and Z height before the part starts, add a brim when corners/edges lift or the footprint is small, and reserve rafts for stubborn adhesion or rough/variable beds because they cost time and ruin bottom finish.

Brims, Rafts, and Skirts (Placement)Topic-specific diagram for the concept, checks, and tradeoffs in this lesson.SkirtLoops not touching partBrimAttached first-layer ringRaftSacrificial base layersPrimingSkirt benefitAnti-warpBrim benefitMax adhesionRaft benefit
Where each helper prints relative to the part: skirt is separate, brim touches the part, raft sits underneath with an interface layer.

What they are (and what they actually do)

Skirt: 1+ loops printed near the model but not touching it. It primes the nozzle and lets you watch the first-layer line quality before the part begins. Brim: extra outlines that are attached to the part’s first layer, increasing contact area and resisting edge lift. Raft: a separate multi-layer “platform” printed under the part; the part prints on a raft interface so you can peel it off later.

Pick the right tool

  • Choose a skirt when you mainly want a startup check: is filament flowing, are lines sticking, and is the nozzle too high/low?
  • Choose a brim when the part can physically lever itself off the bed: sharp corners, long straight edges, tall skinny parts, or small footprints.
  • Choose a raft when you can’t get reliable adhesion any other way, the build surface is inconsistent, or you need a sacrificial layer you can remove (knowing the underside will look worse).

Tradeoffs you’ll notice on the finished part

Skirt
Pros: fastest, no cleanup on the part. Cons: adds zero adhesion to the part.
Brim
Pros: strong anti-warp effect; stabilizes small bases. Cons: you must remove it; can nick/scar the bottom edge if the first layer is over-squished.
Raft
Pros: maximum adhesion and can hide minor first-layer imperfections. Cons: most time/filament; worst underside finish; removal can be tedious if tuned poorly.

Starter settings that work for many printers

  • Skirt: 1–3 loops, 3–10 mm away from the part. Use your normal first-layer speed/temps so it’s a meaningful test.
  • Brim: start around 5–10 mm width (or ~8–20 lines, depending on line width). Add width for sharp corners or warp-prone materials.
  • Raft: use only when needed. Keep it as thin as your slicer allows while still stable, and ensure there is a distinct interface/release layer between raft and part.

If it fails

Skirt prints fine but the part still lifts at corners/edges

Likely cause: The part needs more contact area or the first layer on the part is cooling/contracting too much

Fix: Add a brim; slow the first layer; re-check first-layer squish and bed temperature for that material

Brim is welded on and tears up the bottom edge during removal

Likely cause: First layer is too low (over-squished) and/or first-layer temperature is too hot; brim is wider than needed

Fix: Raise Z offset slightly or reduce first-layer temp; reduce brim width/lines and try again

Raft is hard to remove or leaves a very rough underside

Likely cause: Raft interface is too dense or the gap to the part is too small

Fix: Increase raft air gap and/or reduce interface density; if adhesion is otherwise OK, switch from raft to brim