How does a 3D printer work?

Basically, a 3D printer works much like a well-known 2D printer that applies ink to a paper by means of a jet or laser. The 3D printing is an additive process in which material is gradually added layer by layer to create a three-dimensional model. There are several methods in 3D printing that work slightly differently. The starting point for 3D printing is the corresponding CAD data for the part to be printed.

Stereolithography (SLA)

In this method, a synthetic resin is exposed to a UV laser and thereby cured. The resin is placed layer by layer in a container and each layer is exposed to UV at the desired points. Once a layer has cured, the next step follows after the synthetic resin has been added, and so on. In order to hold the print object from floating or moving in the resin, support structures are needed to fix the object in the synthetic resin bath. These support structures are manually removed by hand after completion of the print.

Selective Laser Sintering (SLS)

In the SLM process both plastics and metals are processed. The material is applied uniformly in powder form layer by layer with a doctor blade or a levelling roller. By means of a laser, the powdery raw material is fused and then the next layer of powder is brushed over it. The material is melted together in layers until the desired component is completed. At the end of a printing process the powder in which the printed components lie is situated in a container, which can be removed from the printer and emptied after cooling. The excess powder is removed and can be reused. The finished components are easily cleaned and can be reworked according to requirements and application. Sometimes depending on the requirement, a subsequent smoothing of the surface is required.

Fused Deposition Modeling (FDM)

In the FDM process, the plastic is used as a filament, rolled up in the form of a wire on a spool. The plastic is melted for processing and dispensed through a nozzle as a thread. This thread is applied endlessly and gradually, the desired component is formed layer by layer. Advantage of this method is that there are printers with two nozzles through which two different plastics can be applied simultaneously. A small disadvantage is the thickness of the applied layers, which are usually recognisable on the finished objects and the surface may need reworking.  

Meanwhile, there are, in addition to the kits for hobbyists, also affordable readymade 3D printers. For private use 3D printers are used almost exclusively in the FDM process.