Additive manufacturing is a form of prototyping or production that functions by adding materials to build a form (think rolling a snowman), rather than subtracting materials (think ice carving). Even the most common form of additive manufacturing, 3D printing, essentially just stacks 2D layers in the same way motion pictures are actually a series of stills.
All additive manufacturing technologies share this same basic functionality – and no matter the technology, all projects begin with a CAD file that is digitally sliced into layers as thin as 0.0006 inches. From there, the actual process of layering or building can be accomplished in a number of different ways:
- A metal plate is submerged just below the surface of a vat of photo-sensitive polymer resin.
- An ultraviolet laser traces the CAD pattern onto the surface. Wherever the laser hits, the uppermost layer of the resin hardens.
- The metal plate is lowered incrementally after each layer so it, again, sits just below the surface of the liquid – and the next layer is built on top of the previous, creating the part from the bottom up.
Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS)
- SLS and DMLS are similar to SLA, but rather than liquid resin, the base material is a powdered material (such as nylon, metals and elastomers) that has been rolled onto a surface.
- The granular material is fused together (or “sintered”) with the heat from an infrared laser beam.
- A roller deposits thin powder layers on top of the previously sintered piece, and laser sintering continues until a 3D piece based on a CAD model is produced.
PolyJet 3D Printing
- Imagine how an inkjet printer works: spraying droplets of ink onto paper in a particular pattern. PolyJet 3D printing is similar.
- In PolyJet 3D printing (and all industrial 3D printing), droplets of liquid photopolymer are jetted from various nozzles onto a build tray following the CAD pattern.
- The liquid resin is instantly cured by UV light, allowing the nozzles to spray the next layer directly onto the previous one.
Fused Deposition Modeling (FDM)
- In FDM, melted plastic filaments are extruded through a nozzle (think of how a hot glue gun works) onto a support structure based on CAD cross sections.
- As each thermoplastic material layer dries, the base is lowered so the next layer can be applied directly onto the previous one.
- The support structure is removed by hand once the part or prototype comes off the machine.
Urethane and Metal Castings
- Casting is primarily used for rapidly creating small-run copies of existing prototypes or parts.
- A mold or “cast” is created with a cavity in the shape of the final part.
- Various materials can then be injected into the mold’s void. Once the material hardens, the mold is removed, leaving only the finished piece.
Which technology a customer chooses is determined by what final attributes are most important to a project. Read last month’s Ask ProtoMAN for details on how to determine which technology is best suited for a particular project.
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