According to an Ultimate3D article, a popular applicatoin of 3D printing in theater is "prototyping" for sets. The article points out works from scenic designers like Kacie Hultgren, who worked on Pretty Small Things.


The site further goes in to the process of using 3D printing in theater: 

"Scenic designers will print their own miniature props to visualize how a finished set will look. After creating a scaled down model of a custom set, they then have something tangible to present to directors and set builders who make the final full-size furniture and props."