3D printing is getting more and moro common and it is expanding from prototyping applications to commercial use, opening up, at the same time, new possibilities.
This is the case of a company in the Netherlands, Luxexcel, that has found a way to print optical surfaces, like lenses.
The problem with 3D printing is that the object is created by layering one layer of the desired substance onto the other. This creates ridges and bumps that don't go well with optical applications.
What Lexexcel managed to do was to invent a process that eliminates these ridges. Basically, they have the 3D printer deploying droplets of material that remain in a liquid state. By careful positioning the object as it is being built the liquid droplets coalesce with one another and can be subject to forces that shape the overall surface. It becomes possibile to obtain the desired, smooth, curvature that is needed in optical applications.
Once the right surface is achieved the liquid is transformed into a solid by applying ultraviolet rays (a well known process to solidify certain kinds of plastic).