3D printing or additive manufacturing

- Apr 11, 2019-

Stereolithography

Stereolithography (SLA or SL; also known as optical fabrication, photo-solidification, solid free-form fabrication and solid imaging) is an additive manufacturing or 3D printing technology used for producing models, prototypes, patterns, and production parts up one layer at a time by curing a photo-reactive resin with a UV laser or another similar power source.

Highlights of Stereolithography:

  • Inexpensive compared to other techniques.

  • Uses a light sensitive liquid polymer.

  • Requires post-curing since laser is not of high enough power to completely cure.

  • Long-term curing can lead to warping.

  • Parts are quite brittle and have a tacky surface.

  • Support structures are typically required.

  • Uncured material can be toxic. Ventilation is a must.

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Selective laser sintering

Selective laser sintering (SLS) is an additive manufacturing technique that uses a laser as the power source to sinter powdered material (typically metal or polymer), aiming the laser automatically at points in space defined by a 3D model, binding the material together to create a solid structure. It is similar to direct metal laser sintering (DMLS); the two are instantiations of the same concept but differ in technical details. Selective laser melting (SLM) uses a comparable concept, but in SLM the material is fully melted rather than sintered, allowing different properties (crystal structure, porosity, and so on). SLS (as well as the other mentioned AM techniques) is a relatively new technology that so far has mainly been used for rapid prototyping and for low-volume production of component parts. Production roles are expanding as the commercialization of AM technology improves.

Highlights of Selective laser sintering:

  • Considerably stronger than Stereolithography; sometimes structurally functional parts are possible.

  • Laser beam selectively fuses powder materials: nylon, elastomer, and soon metal.

  • Variety of materials and ability to approximate common engineering plastic materials.

  • Powdery, porous surface unless sealant is used. Sealant also strengthens part.

  • Uncured material is easily removed after a build by brushing or blowing it off.

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  • Fused deposition modeling

  • Standard engineering thermoplastics, such as ABS, can be used to produce structurally functional models.

  • Two build materials can be used, and latticework interiors are an option.

  • Filament of heated thermoplastic polymer is squeezed out like toothpaste from a tube.

  • Thermoplastic is cooled rapidly since the platform is maintained at a lower temperature.

  • Milling step not included and layer deposition is sometimes non-uniform so "plane" can become skewed.

  • Make rapid progress in past few years and be used widely.

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