Brim, Raft, and Skirt: When to Use Them? A Guide to Adhesion Aids

🔧 Brim, Raft, and Skirt: When to Use Them?

TL;DR: Skirt only primes the nozzle and ensures leveling. Brim, a flat strip added to the base edge of the print, prevents warping and improves adhesion for small parts. Raft adds a full platform beneath the print, providing the best adhesion but reducing bottom surface quality. For most prints, brim is sufficient; use raft only for serious adhesion issues.

📋 Table of Contents

What are Adhesion Helpers?
Skirt: Detailed Review
Brim: Detailed Review
Raft: Detailed Review
Comparison Table
Decision Tree: Which One to Choose?
Slicer Settings
Printer-Specific Notes
FAQ (Frequently Asked Questions)

🔍 What are Adhesion Helpers?

One of the most fundamental problems in 3D printing is the proper adhesion of the print to the build plate. If adhesion is insufficient, the part can detach from the plate, corners can lift (warping), or the print can fail completely.

Adhesion helpers are extra structures that your slicer software adds around or beneath your print. There are three main types:

Skirt: Outline lines drawn around the print
Brim: A flat edge added to the base of the print
Raft: A full platform added beneath the print

Each has its own advantages, disadvantages, and ideal use cases.

📏 Skirt: Detailed Review

What is a Skirt?

A skirt is one or more outline lines drawn around your print. It does not touch the print and does not provide adhesion. It is purely for preparation.

What Does a Skirt Do?

Nozzle Priming: It initiates filament flow from the nozzle before the print starts. This ensures the first layer of the actual print is smooth.
Bed Leveling Check: Skirt lines allow you to observe adhesion in every area of the build plate. If a line doesn't adhere in a corner, you have a chance to correct the leveling.
Filament Flow Verification: You can detect extrusion issues (clogging, insufficient flow) before the print begins.

Skirt Settings

Setting	Recommended Value	Description
Number of Lines	2-3	Sufficient for nozzle priming
Distance (Offset)	3-10mm	How far from the print
Number of Layers	1	Usually, one layer is enough

When to Use a Skirt?

Can be used for every print (should be active by default)
Sufficient on its own for prints without adhesion issues
Ideal for wide-based parts with low warping risk

When is a Skirt Insufficient?

For parts with small base areas
For tall and thin parts
For materials prone to warping (ABS, ASA)
If bed adhesion is already problematic

🔲 Brim: Detailed Review

What is a Brim?

A brim is a flat strip added to the base edge of your print. It is printed at the same level as the first layer of the print and touches the print. Think of it like the brim of a hat.

When to Use a Brim?

When Warping Risk is High:
- Materials like ABS, ASA, Nylon
- Large, flat base areas
- Printers without an enclosure
When the Base Area is Small:
- Models with thin legs
- Small parts
- Geometries with minimal contact with the build plate
For Tall and Thin Parts:
- High height-to-base ratio
- Risk of detaching from the plate due to leverage
When Printing Multiple Small Parts:
- Ensures each part adheres individually

Brim Width Guide

Situation	Recommended Brim Width
Low warping risk	3-5mm
Medium warping risk	5-8mm
High warping risk	8-15mm
Small base area	5-10mm
Very thin/tall parts	10-15mm

Brim Types

Outside Only

Brim is added only to the outer edge of the print
Holes and inner cavities are not affected
Recommended: This option is sufficient in most cases
Easier to remove

Everywhere

Brim is added to both inner and outer edges
Brim is also added inside holes and cavities
Used in very difficult adhesion situations
Harder to remove

Brim Removal Techniques

With a Knife: Separate the brim from the print with a thin craft knife or spatula.
With Pliers: Grip the edge of the brim with pliers and slowly peel it off.
With Sandpaper: Clean remaining brim marks with fine-grit sandpaper (220-400 grit).
Deburring Tool: A plastic edge cleaning tool is very effective.

💡 Tip: Some slicers have a "Brim Gap" setting. Setting it to 0.1-0.2mm can make the brim easier to remove.

🏗️ Raft: Detailed Review

What is a Raft?

A raft is a multi-layer full platform added beneath your print. The print is placed on top of the raft, and after the print is finished, the raft is removed and discarded.

Raft Structure

A raft typically consists of three parts:

Base Layer: Adheres to the build plate with thick lines.
Middle Layers: Form the body of the raft.
Top Layers: The flat surface where the print will sit.

When to Use a Raft?

Very Poor Bed Adhesion: If the bed is uneven or the surface is damaged.
ABS/ASA Prints: For highly warp-prone materials.
Uneven Bed: If a glass bed is chipped or warped.
Very Small Base Area: If even a brim doesn't provide enough adhesion.
If Bottom Surface Quality is Not Critical: If the quality of the bottom surface is not important.

Raft Advantages

✅ Provides excellent adhesion
✅ Largely prevents warping
✅ Compensates for bed irregularities
✅ Eliminates first-layer issues

Raft Disadvantages

❌ Material waste (significant filament is consumed)
❌ Print time increases
❌ Bottom surface quality decreases (raft texture remains)
❌ Can be difficult to remove
❌ Dimensional accuracy may decrease

Raft Settings

Setting	Recommended Value	Description
Air Gap	0.15-0.25mm	Distance between raft and print
Top La
yers	2-3	Number of top layers
Base Layers	1-2	Number of base layers
Raft Extra Margin	3-5mm	Amount of overflow from the print

⚠️ Air Gap is very important: Too low = raft is impossible to remove. Too high = print can detach from the raft.

📊 Comparison Table

Feature	Skirt	Brim	Raft
Adhesion support	❌ None	✅ Medium-Good	✅ Very Good
Warping prevention	❌ None	✅ Good	✅ Very Good
Material waste	Very little	Little	A lot
Additional time	~1 min	~3-5 min	~10-20 min
Bottom surface effect	None	Minimal	Noticeable
Difficulty of removal	Not removed	Easy-Medium	Medium-Difficult
Nozzle preparation	✅ Yes	✅ Yes	✅ Yes
Leveling control	✅ Yes	✅ Yes	Limited

🎯 Decision Tree: Which One to Choose?

Follow the decision process below:

1. Is bed adhesion good?

Yes → Use Skirt
No → Proceed to the next question

2. Is there a risk of warping?

No → Skirt is sufficient
Slight-Medium → Use Brim (5-8mm)
High → Use Wide brim (10-15mm) or Raft

3. Is the base area of the part small?

No → Skirt or thin brim
Yes → Use Brim (8-10mm)

4. Is bottom surface quality important?

Yes → Prefer Brim (raft ruins the bottom surface)
No → Raft can be used

5. Is the bed flat?

Yes → Brim is sufficient
No → Use Raft (compensates for bed unevenness)

General Recommendation by Material

Material	Default Recommendation
PLA	Skirt (brim if there are issues)
PETG	Skirt or brim
ABS	Brim (in an enclosed environment) or Raft
ASA	Brim or Raft
TPU	Skirt (adhesion is usually good)
Nylon	Brim or Raft

🖥️ Slicer Settings

Cura

Build Plate Adhesion Type: None / Skirt / Brim / Raft
Skirt settings: Skirt Line Count, Skirt Distance
Brim settings: Brim Width, Brim Line Count, Brim Only on Outside
Raft settings: Raft Air Gap, Raft Top Layers, Raft Extra Margin

PrusaSlicer / OrcaSlicer

Brim type: No brim / Outer brim only / Inner brim only / Outer and inner brim
Brim width: Set in mm
Skirt: Skirt loops, Skirt distance, Skirt height
Raft settings: Raft layers, Raft contact distance

Bambu Studio

Brim type: Auto / No brim / Outer brim / Inner and outer brim
Auto option makes the decision automatically based on the model
Raft settings are similar to PrusaSlicer

🖨️ Printer-Specific Notes

Bambu Lab (X1C, P1S, A1)

Bambu Lab's PEI bed provides excellent adhesion for most materials
Skirt is usually sufficient for PLA
Brim is recommended for PETG (can stick too much to PEI, use glue stick)
The Auto brim feature usually makes the right decision
If adhesion is difficult on the Cool plate, use the Textured PEI plate

Creality (Ender 3, Ender 5, K1)

If using a glass bed, adhesion aids (glue stick, hairspray) may be needed
Switching to a PEI bed largely solves adhesion issues
Bed leveling can be problematic on the Ender 3 → raft can be used
With automatic leveling on the K1 series, brim is usually sufficient

Prusa (MK3S+, MK4, Mini+)

Prusa's textured and smooth PEI beds provide great adhesion
Do not print PETG directly on a smooth PEI bed (it can stick and damage the bed)
Skirt is usually sufficient for PLA
With the MK4's input shaper, brim usually yields better results

💡 Adhesion Improvement Tips

To increase adhesion without needing Brim or Raft:

Bed cleaning: Clean regularly with IPA (isopropyl alcohol)
Bed temperature: Use the appropriate temperature for the material
First layer speed: Keep it low (15-25 mm/s)
First layer height: Use 0.2-0.3mm
First layer flow: In the range of 100-110%
Z-offset: Adjust the first layer squish correctly
Adhesion aids: Glue stick, hairspray, or specialized 3D printing adhesives

❓ FAQ (Frequently Asked Questions)

Q: I'm undecided between Brim and Raft, which one should I choose?

A: Try Brim first. Brim is sufficient in most cases and uses less material. If Brim doesn't work, switch to Raft.

Q: Can't I always use Brim instead of Skirt?

A: You can, but it would be unnecessary material waste and a hassle to remove. If there are no adhesion issues, Skirt is sufficient.

Q: Does Brim affect the size of the print?

A: Brim is added outside the print and does not affect its size. However, if you are not careful when removing it, you can scratch the bottom edge.

Q: How can the effect of Raft on the bottom surface be minimized?

A: You can reduce raft marks by increasing the Air gap value (0.2-0.3mm). Also, increasing the number of Raft Top Layers (3-4) provides a flatter surface.

Q: Is Raft necessary for PLA?

A: Generally no. PLA is the material with the lowest tendency to warp. Even a skirt is sufficient on a clean PEI bed. You might consider brim only for parts with a very small base area.

Q: What is Brim gap?

A: It's a small gap (0.1-0.2mm) left between the Brim and the print. This gap makes the Brim much easier to remove. It's called "Brim Gap" in Cura; there is no official support for it in PrusaSlicer yet.

📚 Related Guides

This guide was prepared by the 3D-labX community. For your questions, visit our Community Forum page.