One of the characteristics of 3D printing on Fused Deposition Modeling (FDM) printers is the use of support scaffolds to print objects with overhangs. I talk about scaffolds in a previous blog post, About Scaffolds/Supports.
In short, scaffolds are used to support sections of items that aren't supported by lower sections of the object such as overhangs and bridges. Since the material (plastic) comes out as a melted liquid, it needs something underneath it to support it until it cools into a solid again. After the object has been completed, the scaffolds are cut away from the object and thrown away. It can create a fair amount of waste.
The reason that scaffolds are required is because FDM printers only print on 3 axis. They can't re-acclimate the nozzle and build plate so that the lower part of the object can support the overhangs, aka make every surface on the object flat.
While 3d printers have been created using as many as 5-axis, there hasn't been a good system for slicing objects in a way to efficiently use the 5-axis...until now!! Researchers at Penn State have have developed an automated system that eliminates the need for scaffolds by breaking the object into smaller pieces so that the system can print each section on a different axis.
The article has a great graphic that helps to explain how it works. Check it out: https://gizmodo.com/researchers-find-a-faster-more-efficient-way-to-3d-pri-1845992030.