This process is called (FDM Fused Deposition Modeling) where a thread of molten plastic builds the object layer by layer. A MakerBot was used to make this piece. I modeled the part in 3D CAD, and my friend printed it on his MakerBot.
The plastic is ABS like Lego building blocks. It isn"t quite that strong due to the multiple layer build instead of a solid casting. It worked fine in this application.