Stereolithography 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.
History The term “stereolithography” was coined
in 1986 by Charles W. Hull, who patented it as a method and apparatus for making solid
objects by successively "printing" thin layers of an ultraviolet curable material one on
top of the other. Hull's patent described a concentrated beam of ultraviolet light focused
onto the surface of a vat filled with liquid photopolymer. The light beam draws the object
onto the surface of the liquid layer by layer, and using polymerization or cross-linking
to create a solid, a complex process which requires automation. In 1986, Hull founded
the first company to generalize and commercialize this procedure, 3D Systems Inc, which is currently
based in Rock Hill, SC. More recently, attempts have been made to construct mathematical models
of the stereolithography process and design algorithms to determine whether a proposed
object may be constructed by the process. Technology
Stereolithography is an additive manufacturing process which employs a vat of liquid ultraviolet
curable photopolymer "resin" and an ultraviolet laser to build parts' layers one at a time.
For each layer, the laser beam traces a cross-section of the part pattern on the surface of the
liquid resin. Exposure to the ultraviolet laser light cures and solidifies the pattern
traced on the resin and joins it to the layer below.
After the pattern has been traced, the SLA's elevator platform descends by a distance equal
to the thickness of a single layer, typically 0.05 mm to 0.15 mm. Then, a resin-filled
blade sweeps across the cross section of the part, re-coating it with fresh material. On
this new liquid surface, the subsequent layer pattern is traced, joining the previous layer.
A complete 3-D part is formed by this process. After being built, parts are immersed in a
chemical bath in order to be cleaned of excess resin and are subsequently cured in an ultraviolet
oven. Stereolithography requires the use of supporting
structures which serve to attach the part to the elevator platform, prevent deflection
due to gravity and hold the cross sections in place so that they resist lateral pressure
from the re-coater blade. Supports are generated automatically during the preparation of 3D
Computer Aided Design models for use on the stereolithography machine, although they may
be manipulated manually. Supports must be removed from the finished product manually,
unlike in other, less costly, rapid prototyping technologies.
Advantages and disadvantages One of the advantages of stereolithography
is its speed; functional parts can be manufactured within a day. The length of time it takes
to produce one particular part depends on the size and complexity of the project and
can last from a few hours to more than a day. Most stereolithography machines can produce
parts with a maximum size of approximately 50×50×60 cm and some, such as the Mammoth
stereolithography machine, are capable of producing single parts of more than 2 m in
length. Prototypes made by stereolithography are strong enough to be machined and can be
used as master patterns for injection molding, thermoforming, blow molding, and various metal
casting processes. Although stereolithography can produce a wide
variety of shapes, it has often been expensive; the cost of photo-curable resin has long ranged
from $80 to $210 per liter, and the cost of stereolithography machines has ranged from
$100,000 to more than $500,000. Recently, renewed public interest in stereolithography
has inspired the design of several consumer model printers with drastically reduced prices,
such as the Ilios HD by OS-RC, the Form 1 by Formlabs, the Titan 1 by Kudo3D, the Pegasus
Touch by FSL3D and the Nobel 1.0 by XYZPrinting. There has also been a drastic reduction in
the cost of photo-curable resins, with USA based providers such as MakerJuice Labs offering
materials as low as $40 per liter and European based providers such as spot-A Materials offering
materials for €68 per liter. See also
Stereolithography References
Notes
External links Ilios modular 3d Printer by OSRC with industrial
grade motion, fully metallic construction and highly accurate repeatability rates
Super Precise Kudo3D Titan 1 SLA 3D Printer Hits Kickstarter on May 27 Starting at $1899
Pegasus Touch by FSL3D Laser SLA 3D Printer: Low cost, High Quality on Kickstarter
Formlabs Form 1 a low cost Stereolithography printer being designed and fabricated as a
Kickstarter project How Stereolithography Works from HowStuffWorks.com
Rapid Prototyping and Stereolithography animation – Animation demonstrates stereolithography
and the actions of an SL machine Video of micro-stereolithography for biomedical
applications