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3D resin printing is one of the most popular processes between additive manufacturing services—3D printing online use for the manufacture of prototypes or final pieces. 3D Systems founder Chuck Hull coined the term stereolithography in early 1986.
The basic principle of this technology base on the solidification hardening of a liquid, or paste, monomer by exposure to an ultraviolet light source.
Although the best-known process is the SLA 3d printing, which uses a laser for solidification, currently other processes coexist with that one, such as those based on mask or print head methods. In this article, we will describe the most widely used industrial processes.
3D resin printing: laser stereolithography or SLA
The 3D printers resins or 3D Printing SLA using a laser to polymerize the polymer consist of a container, a construction platform with vertical movement within the container, and the laser unit that describes the laser’s paths to form the layer solidify. The first layer will form on the construction platform. Then said the platform would lower a distance known as layer thickness. It will be the laser that re-solidifies a new layer on top of the previous one. This will generate the 3D model that will submerge in the container. The form labs printer is an example of an SLA technology resin 3d printer.
The resins SLA printer usually epoxies. Only lasers are capable of providing the necessary polymerization energy for epoxy resins.
It is common to manufacture hollow parts in resin 3D printing, saving time and material. To do this, it is necessary to make exit holes for the non-solidified resin inside. These holes must close a posteriori if the models use for casting processes with models lost in the ceramic or refractory lining.
Finished parts require post-processing to remove resin residue and support construction. For cleaning, the pieces place in a container with a solvent such as isopropyl alcohol. Laser-based stereolithography
Methods generally do not polymerize the component completely. Therefore a post-curing process is essential, which consists of introducing the part in a chamber with a UV light source for a controlled time and temperature.
The models made of resin have very details and the best of the surface finishes compared to the rest of the additive manufacturing processes. On the other hand, a disadvantage present in the mechanical characteristics that have improved considerably in recent years does not reach those of the plastic parts obtained in injection molds.
Resin 3D Printing: Digital Light Processing or DLP
The 3D printers’ DLP resins are technologically very similar to the SLA. They base their manufacturing principle on the mask method.
The main difference is the use of a DLP projector through a lamp. The use of the projector allows exposing a cross-section completely and therefore solidifying a complete layer at the same time regardless of the number of components that manufacture.
As in SLA, the material for the part and supports is the same. Therefore, they must be removed afterward, before or after cleaning and curing.
Another DLP variant has a construction platform that moves from the bottom up. Said platform immerse in a container whose base has a glass. The projector emits the cross-section through the bottom of the container and solidifying the first layer. The build platform rises a distance equal to the layer thickness to let the resin flow solidify in a second layer. Thus, layer by layer, the platform goes up, generating the 3D model. An advantage of this process is that it requires a small amount of resin.
The resins used in this technology are of the acrylates type because the lamps do not provide as much energy as an SLA laser.
