Raft in 3D printing: a base under the part, what it brings and what it costs

How a raft works

Several dense layers are printed first under the part, forming a board larger than the part itself. The model is then printed on it with a small gap so that it can be separated later. The setting in the slicer is described in the OrcaSlicer wiki.

It is used for parts with a small or uneven bottom surface, for materials prone to warping or for an uneven bed. With ordinary PLA and PETG on a clean PEI plate it is mostly not needed.

Disadvantages of a raft

• The underside of the part is rougher, because it is printed on the raft and not on the smooth bed.
• It uses more plastic and more time, with larger parts tens of minutes.
• It has to be snapped off after printing, which leaves marks on the underside, especially with PETG, which holds more firmly.
• The underside is less accurate, which matters for mating surfaces and tolerances.

What to do instead of a raft

Usually it is enough to turn the part so its largest flat surface is down, see model orientation. A brim can help too, or splitting the part into several flat pieces that are then glued together.

Raft with PLA and PETG. With PLA a raft is rarely used, because PLA holds well directly on the bed. PETG sticks so strongly that a raft or a support is harder to snap off after printing and can leave marks. It is therefore better to turn the part so it has a flat, large bottom. If that cannot be avoided, expect a rougher underside and do not put dimensionally accurate surfaces on the bottom.

A raft in your order

A raft is not an option in the calculator. We prepare the print settings ourselves, and all you choose is the material, the infill strength, the scale and the number of pieces. If your part is sensitive about its underside, design it with a flat and sufficiently large bottom, or write to us at jakub.novak@boostello.com.