Overhangs in 3D printing: when you need supports and how to avoid them

What angle can still be printed

In FDM printing every layer sits on the one below. If a wall leans out only slightly, the new layer mostly rests on the old one and holds. The more it leans, the more plastic hangs in mid-air.

The usual rule of thumb is about 45 degrees from vertical. Up to that angle you can print without support and the surface comes out clean. Beyond it the plastic starts to droop and the underside gets rougher, see sagging overhangs. Horizontal spans across a gap are a bridge.

How the print handles it

Wherever an overhang goes past the allowed angle, the slicer adds supports. They are removed after printing, and the spot where they sat is rougher than the rest. We generate supports automatically and their cost is included in the price per piece.

Supports cost material and time, so a model with large overhangs costs more than the same shape without them. You see the exact price right after uploading.

How to design overhangs out

• Rotate the model. Often it is enough to change which side it lies on and the overhang disappears. See model orientation.
• Chamfer the edge. Replace a horizontal edge with a 45 degree chamfer instead of a round.
• Use a teardrop shape. A horizontal round hole with a point at the top prints without support.
• Split the model. If nothing else works, cut it into parts and glue them together, see splitting a model.

Worth keeping in mind

A very long overhang beyond 45 degrees may not come out clean even with supports. So do not put a smooth show surface on the side that will be overhanging. If you are not sure, email us at jakub.novak@boostello.com and we will suggest how to turn the model.