3D Printing has many years of being a very productive technology. It is not a technology that has been made for printing, even though it is called 3D printing. It is much more, because it makes objects out of more than hundred different materials, including liquid.
A very useful technology in 3D printing is SLA. SLA is an abbreviation of Stereolithography. It is a main technology that also include photopolymerization being used for producing a solid part from liquid material. It requires using supporting structure, as it is attaching the part to the platform that elevate the layers.