3D printing can be a bit of an overwhelming experience for the new enthusiast. There are dozens of new terms, a spiky learning curve, and at least a couple of meaty programs that you’re going to need to learn before you can make it very far. And, while temperature might be the most difficult to pin down at first, it’s really the problem of infill and supports that stumps the average newbie.
Infill is exactly what it sounds like, though: something that fills something else in.
For most models of any reasonable size, there needs to be some sort of interior support to keep the middle of the model from sagging under its own weight.
Now, when you print a model you could print it solid (which would mean that you’re printing just one large piece of plastic), but if you do print a solid model you’re going to use a massive amount of filament and your prints are going to take a long time. That’s why, most of the time, people print using one of the infill settings available in their Slicer program.
Infill comes in two important categories: density and pattern. Density is just how much plastic you want sitting, hidden, inside your model. Pattern is just the setting for what shape that hidden plastic takes. There are various benefits to different types of infill, from strength to printing speed, but the gist is that all of them use a lot of plastic to create some type of interior structure that supports your 3D print from the inside-out.
But using infill, even on lower settings, still takes a massive amount of plastic filament to print, and even the fastest options for infill patterns are going to add an increasing degree of time to your prints (after all, your printer has to spend a lot of time printing those internal support structures, which can quickly take up for material and time than the outer shell that you actually care about!).