Most 3D printing processes can be modeled by an incremental
stacking of thin, flexible layers. In this case, it is apparent that for
complex shapes, some stacks will be ”floating” in mid-air unless
they are supported from below by additional material. Similarly if
a slice is much larger than the one below it, it will droop unless supported. These areas are called overhangs, and most
3D printing software provides automated generation of some kind
of support structure. However, the support is waste, of both time
and material, and this waste should be minimized.