There are a number of good
surveys of 3D printer technology, including commercial
choices that are fridge-sized and cost from $15K-$1M.
|Inkjet powder printing
Polyjet (thin layer)
(SLA) uses an optically sensitive material, typically a vat
of UV-curable photopolymer, to selectively cure 2D slices into a
3D object. Speed and accuracy can be excellent depending on
the optics used, in particular with newer digital light processing
(DLP) projector chips, but the cost of the photopolymer is fairly
high (at least $65/liter or Kg), and most photopolymers result in
objects that are not
very impact-resistant. SLA was one of the first 3D
printing technologies, and still dominates for small-size
high-precision work. The standard file format "STL"
(STereoLithography) derives its name from this technique.
printers use a similar photopolymer to SLA, but use inkjet-type
technology to spray the photopolymer onto the object before
curing. This allows them to use a wide variety of materials,
including rubbery materials, and to grade materials into one
Direct Metal Laser Sintering (DMLS) or the higher temperature Selective Laser Melting (SLM) uses a laser to fuse a flat bed of powder or a gas-carried stream of powder into a solid, depositing material layer by layer. With an inert atmosphere and high temperature chamber, this can be made to work with metals, including steel and aerospace metals like titanium or inconel. This also provides automatic support structure, since the powder is deposited at the same time as the part. Electron Beam Melting (EBM) uses an electron beam for the same purpose, but requires a vacuum chamber.
Deposition Modeling (FDM) (or the generic term Fused
Filament Fabrication / FFF) deposits a semi-solid material onto a
build platform to assemble the shape, and is the dominant
technology for home 3D printers. Unlike SLA, it is inherently a 1D
fabrication process, since the material emerges in a single
line. Most models work by feeding a filament into a hotend,
but this is only suitable for materials that have a viscous
intermediate state--this includes most plastics, chocolate, and
even glass when using a sufficiently hot hotend, but the low viscosity of most
molten metals makes them unsuitable for FDM/FFF.
Another option is to extrude self-curing materials like epoxy or
cement. Advantages include inexpensive filament feedstock
(as low as $20/Kg), and simple heating elements can be home
fabricated, unlike lasers or optics.
acid, plus plasticizers
rubber plus acrylonitrile
dioxide with boron or sodium flux
|w/ alloying copper,
|w/ alloying zinc, silicon
|w/ alloying carbon,
Many filaments are actually alloys of different substances--in
particular, ABS, HDPE, and polycarbonate will intermix well.
And there are a variety of "improved"
filament chemistry options.
Filament makers can also add small particles of various filler
materials to the plastic matrix:
A key technology for designing toolpaths is calculating material flow rates: