What is 3d printing?
https://www.3dhubs.com/what-is-3d-printing
3d printing material - Proto Labs.
https://www.protolabs.com/documents/united-states/3D-Printing-Decision-Tree-Infographic-Horizontal-us-Full-Final.pdf
http://www.appliancedesign.com/ext/resources/WhitePapers/2016/3D-Printing-Materials-WP-US-Final.pdf