How does a 3D printer work? - Clearly explained

3D printers are becoming cheaper and more interesting for private users. We explain how a 3D printer works and what different printing methods are available.

Basic functionality of 3D printers

There are currently three different 3D printing techniques. They differ in the starting material used and the modeling technique. The basic principle is always the same:

• The template for 3D printing is not a text file as with ordinary printers, but a 3D template as it can be designed with CAD software.
• The most common file types are STL (Standard Triangulation Language), VRML (Virtual Reality Modeling Language) and X3D (Extensible 3D).
• The 3D printer is "fed" with these templates. The model is then built from meltable materials, powder or a certain liquid.
• All three common 3D printer types apply thin layers that are individually hardened.

3D printer: how does stereolithography work?

Stereolithography (SLA) was developed back in the 1980s and is the oldest 3D printing technology.

• Liquid epoxy resin, which is located in a basin, serves as the starting material.
• There is a lifting platform in the pool that can be moved up and down. The 3D model is created on this.
• At the start of printing, the lift is just below the surface of the resin - about 0.05 to 0.25 mm.
• A laser, which is attached above the pelvis, hardens the first layer of the model.
• Now the lift moves down a bit. Depending on the printer type and the filigree nature of the model, the layers are 0.05 to 0.25 mm thick. The epoxy resin runs together over the first, already hardened layer.
• Now the next layer of the object is hardened and fits seamlessly onto the first, underlying layer.
• The 3D model is built up layer by layer from bottom to top.
• The advantage of the SLA process is the smooth surface of the model. However, the liquid does not carry overhanging parts as long as they are not fully hardened. For this reason, support structures may have to be used.

How does a 3D printer work ?: Laser sintering

Selective Laser Sintering (SLS) or Selective Laser Melting (SLM) uses a powder as the raw material. Polyamide 12 powder is mostly used. However, molding sand coated with plastic and metal or ceramic powder are also possible as the starting material.

• Laser sintering uses not only one basin, but two basins arranged next to each other, each with a lifting platform.
• The powder is the raw material in a basin (left in the picture).
• A roller picks up the powder and rolls it over the lift in the neighboring pool, which is at the top at the beginning.
• A laser melts or sinters the powder (in the case of ceramics) so that it binds and hardens. The first layer of the object is created.
• The lift in the powder basin moves up a little, the one in the object basin lowers a bit.
• The roller applies the next layer of powder to the first, hardened layer of the object and the laser starts to harden again.
• So the model is built up layer by layer from bottom to top.
• The advantage of the process is the versatile choice of materials. In addition, no supports need to be arranged, since the powder is hardened immediately and load-bearing.
• In contrast to stereolithography, the objects have a rough surface during laser sintering. The printers are also very expensive and are therefore more developed for industry.

Fused Deposition Modeling (FDM): 3D printers for private users

Fused deposition modeling (FDM) is the most widespread method.

• Materials are used that become liquid or moldable under heat - for example thermoplastic materials such as PVA, PET and nylon, but also chocolate and wax.
• The material is heated in a nozzle and liquefied. Then it is applied to a layer at certain points - very similar to classic printing - and then cooled so that it hardens.
• As with the other processes, this creates one layer after the other.
• Another disadvantage is that the model does not harden completely immediately. For this reason, support structures may have to be planned in.
• But printers and materials are relatively cheap, so they are also suitable for private users.