Raft and Brim

Theory

A brim is a flat single-layer skirt attached to the model's perimeter, extending outward (typically 5-20 mm). It increases contact area with the bed and anchors corners prone to lifting. A raft is a thick multi-layer platform printed underneath the entire model; the model prints on top of the raft. Rafts provide maximum adhesion and compensate for uneven beds but add material and post-processing time.

Application

Use brim for tall, narrow, or warp-prone prints (ABS, ASA). Set brim width to 8-10 mm for most cases; increase to 20 mm for extreme warping. Use raft for flexible filaments that struggle with direct bed adhesion, or when the print footprint is very small. Remove brim carefully with flush cutters or a sharp blade; rafts peel off more easily if interface layer air gap is set to 0.3 mm.

Common mistakes

Brim on fine-detail parts near the model perimeter can fuse to small features, requiring careful removal. Rafts add significant print time and material waste. Skirt (non-attached) is sometimes confused with brim: it provides no adhesion benefit. PEI surfaces usually do not need brim for PLA; adding one increases removal difficulty.

Related terms: Warping, Bed Adhesion, Elephant Foot