Raft

A raft typically has 3–5 layers: a wide, fast-printed base layer for grip, one or two interface layers, and a thin top layer that peels away from the part cleanly. The part adheres to the raft rather than the bed, so heat-affected warping is somewhat isolated from the build surface.

Rafts are the heavy-duty answer for materials and parts where even a brim is not enough. ABS, ASA, and nylon on a borderline bed all benefit. Tiny parts with little contact area also benefit because the raft gives the part a much larger effective footprint.

The cost is real: a raft adds 5–15 minutes of print time, uses extra filament, and leaves a slightly rough underside on the part where it peeled away. For most users on a well-tuned printer with PEI or textured glass, brims are sufficient and rafts are rarely necessary.

Rafts were essential on early printers with marginal beds. Modern printers with magnetic flex plates, PEI, or textured-glass beds rarely need them. If you find yourself using rafts routinely, your bed leveling, first layer height, or bed surface probably needs attention.