3D printing is not one thing, the different technologies depend on may factors; application, accuracy, price, output volume, materials and user expectations.
3D printing is a range of technologies that are essentially a 3D output device for CAD files. There are 9 different types.
1. Stereolithography (SLA)
2. Digital Light Processing (DLP)
3. Fused deposition Modeling (FDM)
4. Selective Laser Sintering (SLS)
5. Selective Laser Melting (SLM)
6. Electronic Beam Melting (EBM)
7. Laminated Object Manufacturing (LOM)
8. Binder Jetting (BJ)
9. Material Jetting