There are many 3D printing technologies available today. I am going to point your attention towards the one, that is considered the first 3D printing process and the first to be commercialized- Stereolithography. Stereolithography or SL in short, is a 3D printing method, where a laser works with photopolymer resins, that react with the laser and cure to form a solid, in a very precise way to create very detailed parts. This process is very complex. The photopolymer resin is held in a vat with a movable platform inside. A laser beam is directed in the X-Y axes across the surface of the resin, that follows the path which was set in the .stl file created by the 3D modeling software, then the resin hardens exactly where the laser hits the surface. When the first layer is complete, the laser prepares to start forging the next layer, as the platform which is withing the vat slightly drops down in the Z axis to make space for it. This operation is repeated until the object is entirely complete and once finished the platform can be raised out of the vat and removed. The SL process requires support structures for some parts, because of its nature, and especially if these parts have overhangs or undercuts. When the operation is complete these parts need to be manually removed. Many, of the objects printed with SL, need to be cleaned and cured once they are complete. The aim of this process is for the resin to fully harden.The process of curing these parts involves a machine similar to oven, where the object is exposed to intense light.
SL is considered to be one of the best 3D printing processes in terms of accuracy, when it comes to the surface finish of the process and are commonly used for highly detailed sculptures, jewelry molds, and prototypes. DLP is also a very good option for these objects. However using them for 3D printing big objects is not advisable as the DLP machines are small.
Digital Light Processing or DLP is another process that creates 3D printed objects from a photopolymer resin, by using a light source to solidify the liquid material, just like SL. However there is a difference when it comes to the light source that is used for solidification. With them being the two most common methods when it comes to light source SL uses a laser, while DLP uses projector. While there are not many options in terms of materials, recently more variety was added providing either more strength or flexibility to the final object. Desktop 3D printers using the SL technology are available.
Lets have a little comparison between DLP and SL. The DLP use stranded projectors. That means that when the light source burns out you can easily replace it, while if there is a problem with the laser of the SL printer in some cases replacing it can be problematic. Then again DLP 3D printers are bigger than SL ones. SL is much older and tested than DLP. It has been used ever since the middle of the 80s, while DLP came to be around 4 years ago. Both SL and DLP use nearly the same number of resins.
Both of these technologies can do outstanding job, 3D printing you the object you desire and the differences between them are not that big. Whichever type you prefer of the two you will not be in the wrong.