If you’re looking for a smooth surface and high precision models, resin technology (such as Figure 4, DLP, SLA) is for you.
This 3D printing process works by hardening layer after layer of a liquid resin. When exposed to a source of light, the photopolymer cures, hardening and linking to the previous layer. Following each layer, a recoater wipes new material on the surface, in preparation for the next layer to be cured.
Similar to FDM, if your model has overhangs, you’ll need to print a supporting structure. As this structure consists of the same material as the model, it has to be mechanically removed.
Unlike FDM, the entire model consists of full material strength. With resin technology you can 3D print elastic and transparent plastics, casting wax and models with very high surface quality.
Within the realm of SLA 3D printing is digital light processing (DLP + Figure 4). It is essentially the same as SLA but uses a projector as a light source instead of a laser. The primary difference is that DLP printing can be faster, given that an entire layer can be exposed to UV light at once.
Figure 4 is the newest generation of resin technology, capable of printing in high speed, with high accuracy and detail up to 10 microns. It offers repeatablity, in materials for various applications, with mechanical properties, such as ABS and PP, high temprature, biocompatible, and end use parts.