Final answer:
A 3D model with an overhang of more than 45 degrees requires supports to prevent the layers from collapsing during printing. Supports are temporary structures removed after printing is complete.
Step-by-step explanation:
A 3D model that has an overhang of more than 45 degrees needs supports. In 3D printing, overhangs that exceed a 45-degree angle typically cannot be printed without additional structures to prevent the layers from collapsing or drooping during the printing process. Supports provide a temporary platform for the overhangs to be built upon. Once the print is completed, these supports can be removed. It's important to use supports wisely, as excessive support can waste material and make post-processing more challenging, whereas too little support can lead to print failure.