There are several different 3D printing technologies or additive manufacturing processes that are similar but have slight differences in their methods used to make a 3D object. The most popular 3D printing technologies are Fused Deposition Modelling (FDM), Selective Laser Sintering (SLS) and Stereolithography (SLA).
Fused Deposition Modelling (FDM)
FDM is the most common technology used in consumer grade 3D printers due to its relatively inexpensive setup. It works by pushing initially solid material (usually ABS or PLA) through a heated extruder nozzle, this turns the material into a thick viscous liquid, and the liquid material is then pushed out onto the build plate. The extruder than moves around the build plate pushing the melted plastic on as the first layer, similar to how your home/office paper printer would lay down ink. However, instead of stopping after one layer as your paper printer would, the 3D printer keeps adding successive layers. As the previous layer is cooling the next layer is being added on top ensuring a strong bond is created as the 2 layers join together. This continues until the whole 3D object has been created, the layers continue to cool throughout the printing process so when the final layer has been extruded the rest of the object is solid and ready to be removed from the printer.
Selective Lase Sintering (SLS)
SLS technology is typically used in professional and more expensive 3D printers due to the more expensive components required. A high powered laser in these types of 3D printers are used to fuse small particles together to form the desired solid object. The process begins by the printer laying down a bed of powder and then the print head (using the laser) will fuse the first layer together. Then a new layer of the powder will be spread over the original layer and the print head will fuse this layer to the existing layer. The process is repeated until the object is completed. One of the main advantages of the SLS process is that all the untouched powder is used as a support structure for the 3D object. This means that complex part geometries and designs can be made without a large amount of post processing of the object. The unused powder is brushed off and can be used for the next print job. SLS is the process used to create metal products and has been used to create body part replacements such as spinal implants and parts for aircraft.
SLA technology uses photo polymerization to change a UV curable liquid into a solid. An ultraviolet light is used on a photopolymer resin that is a curable liquid to construct the required object’s layer one after another. The light beam is used to trace a cross section on the liquid resin’s surface. This exposure to the ultraviolet light solidifies and cures the cross section traced and joins it to the previous layer. After the tracing, the elevator platform moves up by a single layer thickness and the next layer is exposed to the light. The process is repeated until the desired object is formed. Because the raw printing material is a liquid until it is cured, this type of printing requires support structures for complex overhanging geometry. There are many slight variations on SLA technology based on proprietary methods that all promise higher speeds, better layer resolution (smoother finish more like injection molding) and the ability to print many different materials. One of the recent exciting advances is from Carbon3D who demonstarted speeds 10X faster than previous SLA machines.
Advances in 3D printing are occurring rapidly as companies and people realise how important this technology is becoming. See our related blog post on Materials for 3D printing (coming soon).