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Whether metals or plastics, the principle of additive manufacturing by 3D printing is simple.
Every manufacturing technology has certain framework conditions under which it achieves the best cost-benefit ratio. Where does industrial 3D printing score points?
The Selective Laser Sintering (SLS) process uses aP powdered polymer build material, typically nylon, is transferred from containers holding fresh powder material onto the build stage in the process chamber with a recoating tool. A highpower laser then selectively scans the thin layer of powder, sintering together powder particles in the shape of the cross-section of the first layer of the 3D part. The build platform then descends one layer depth and the recoater transfers more fresh powder from the hopper to the surface of the first layer. Just like the first layer, the second cross-section of the 3D model is scanned and sintered. The laser scanning process simultaneously generates the current layer and adjoins it to the previous layer, making a solid part.
Compared to other additive manufacturing processes such as stereolithography (SLA) and Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF), Selective Laser Sintering (SLS) does not require support structures since the powder acts as self supporting material. This allows intricate and complex geometries to be constructed.
FDM is the abbreviation for Fused Deposition Modeling. In FDM, a strand of material (in this case: thermoplastics) is deposited in layers to create a 3D printed object. During printing, the plastic filament is fed through a hot extruder where the plastic gets soft enough that it can be precisely placed by the print head. The melted filament is then deposited layer by layer in the print area to build the workpiece.
There is a broad choice of FDM 3D printers for every budget, starting at a few hundred dollars. Filament spools are relatively inexpensive, starting from $25 per kilo. These factors made FDM printers so popular among makers and home users.
SLA is the abbreviation for Stereolithography Apparatus, or simply stereolithography. Like FDM, SLA is an additive method: Models are built layer by layer. SLA, however, uses a curable photopolymer – typically a liquid resin – that is hardened by applying focused light or UV light (this process is called curing). SLA printers usually build the models from top to bottom, the build platform lifts the model upwards, out of the resin bath.
The light source is either a laser or a digital projector (the technology is often called DLP – Digital Light Processing). Lasers „draw“ the layers; in DLP, an entire slice (a two-dimensional layer) of the model is projected at once into the resin bath.
Laser SLA printers are usually slower than DLP models because of the small surface of the laser beam. In DLP printers, each layer hardens faster as the entire image of one layer is projected onto the resin. Moreover, DLP projectors are more reliable and easier to maintain than customized laser systems as the projectors use the same technology as business and home cinema projectors. The printed models have to undergo a post-processing process, though.
Overall, there are less budget-friendy SLA machines than FDM 3D printers. Resin printers can often be found in a professional context, although the prices came down in the last years.