I would like to know about the average amount of overhang that can be allowed with a required support structure of some kind. I'm trying to design some new types of things, but this would really help
One of the most important things here is to know your printer - Some printers handle overhangs better than others. You often hear that anything more than a 60 degree angle from the horizontal needs to be supported, but I've used printers that can achieve much more than that. If you search Thingiverse for "overhang" you'll find plenty of test pieces where you can find out what your machine is capable of. Your results will depend on the material and the printing profile. For example, i got better results printing PETG when I increased my cooling.
If your overhang is supported on two sides, like a bridge, then you can get much bigger overhangs - you'll need to look at the bridging settings in your slicer.
From the design point of view, it's always a good idea to try to "design out" overhangs. Sometimes this can be as easy as printing the model from another side, but often the simplest solution is to make the piece in two parts.
Hope this helps!
Here's an article for you to read up on. https://www.3dhubs.com/knowledge-base/supports-3d-printing-technology-overview it explains when to use supports. Rule of thumb any horizontal overhang requires support of some kind. My personal work around is to create a slight angle, the printer then can build outwards with no drooping.
With good supports, you can print almost anything. The problem is removing the supports after.
I try to avoid using supports wherever possible. Sometimes you can get way without supports, sometimes you absolutely need them.
Example, printing something hollow with a flat roof. If the distance between the walls is not too great, you might be able to get way without any supports, although the underside of the roof might not look great. Smaller layer heights are good.
Things with circular holes through a vertical surface are usually ok without supports.
Cura's supports are a bit 'all or nothing', I sometimes use Print Studio (free from AutoDesk), lets you add supports manually where you need them.