Supports: what holds up the overhangs during printing

What supports are for

In FDM printing every layer rests on the one before, and the printer cannot print into thin air. When a part has an overhang, such as an arm, a canopy or the underside of a bridge, a temporary support has to be built under it. Those are called supports and they are snapped off after printing.

Supports can be classic, like a dense forest of columns, or tree supports, which branch only where needed. Short horizontal bridges between two supports can be printed without them.

Who deals with supports and what they cost

You do not have to add them to the model. When we prepare the model for printing, supports are generated automatically where they are needed. Their material and print time are already in the price you see in the calculator.

You do have to allow for them in appearance, though. The surface the supports touched is rougher and may keep small marks. So it pays to design the part so that supports are needed as little as possible, or touch only surfaces that will not be seen.

How to design a part without supports

• A slope up to 45 degrees. Overhangs sloping up to roughly 45° from the vertical usually print without supports, as each layer still rests on the one before.
• A chamfer instead of a flat overhang. Chamfer an edge that would hang horizontally. A chamfer under 45° prints cleanly, while rounding towards the bed is a problem.
• Flat side down. The part should lie on its largest flat surface. That surface is then perfectly smooth and supports are mostly not needed at all.
• Split in two. A complex shape is sometimes worth splitting and gluing or screwing together after printing.

There are more tips in the Prusa guide Modeling with 3D printing in mind.