Raft vs Brim in 3D Printing: Understanding the Key Differences

In additive manufacturing, the choice between a raft and a brim can significantly influence print quality, adhesion, and post‑processing effort. Both structures act as a foundation, yet they serve distinct purposes and exhibit different mechanical interactions with the printed part.

What Is a Raft?

A raft is a three‑layered, flat mesh that is deposited first. It is slightly larger than the initial layer of the part, providing a stable base that compensates for bed warping or uneven leveling. Because the raft sits directly beneath the model, it encourages strong adhesion throughout the first few layers.

What Is a Brim?

Unlike a raft, a brim is a single‑layer extension that surrounds the initial perimeter of the print. It does not extend under the part but rather expands outward, creating a “skirt”‑like collar that improves bed adhesion and reduces warping for overhangs and narrow features.

Key Differences

• Location: Raft – underneath the part; Brim – around the part’s perimeter.
• Layers: Raft – typically 3–5 layers; Brim – 1 layer.
• Purpose: Raft – provides a robust, even base; Brim – anchors the outer edges to mitigate warping.

Why Rafts Often Prevail

Rafts deliver superior adhesion because the first few layers of material bond both to the print bed and the raft itself. This dual bonding reduces the chance of the part lifting during printing. The trade‑off is that detaching a raft requires more force, and it adds extra material and print time. Nevertheless, many manufacturers favor rafts for complex geometries or when bed adhesion is a critical concern.

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