A raft is a removable base structure that's printed underneath a 3D model to improve bed adhesion and prevent warping. It consists of several layers of material that create a stable foundation for the actual print, helping to ensure successful first layers and overall print stability.
Rafts are particularly useful when printing models with small contact areas with the bed, complex geometries, or when using materials that are prone to warping like ABS. The raft provides a larger surface area for adhesion and helps distribute the stresses that can cause warping during the printing process.
The raft typically consists of two parts: a base layer that adheres to the print bed and an interface layer that connects to the actual model. The base layer is usually printed with wider lines and higher flow rates to ensure good bed adhesion. The interface layer is printed with smaller lines and lower flow rates to make it easier to separate from the model.
Raft settings can be adjusted in the slicer software, including the number of base layers, interface layers, and the air gap between the raft and the model. The air gap is crucial - too small and the raft will be difficult to remove, too large and the model may not adhere properly to the raft.
While rafts improve print reliability, they do have some drawbacks. They use additional material and increase printing time. They also leave a rougher surface on the bottom of the model where it was attached to the raft. For models where the bottom surface appearance is important, other adhesion methods like brims or skirts might be preferred.
Rafts are especially valuable for beginners or when printing with challenging materials, as they provide a more forgiving printing surface and help prevent common first-layer issues.
