Stereolithography
(SLA) is often considered the pioneer of the Rapid Prototyping
industry with the first commercial system introduced in 1988 by 3D
Systems. The system consists of an Ultra-Violet Laser, a vat of photo-curable
liquid resin, and a controlling system.
A platform is lowered into the resin (via
an elevator system), such that the surface of the platform is a
layer-thickness below the surface of the resin. A laser beam then
traces the boundaries and fills in a two-dimensional cross section
of the model, solidifying the resin wherever it touches. Once a
layer is complete, the platform descends a layer thickness, resin
flows over the first layer, and the next layer is built. This process
continues until the model is complete.
Once the model is complete, the platform
rises out of the vat and the excess resin is drained. The model
is then removed from the platform, washed of excess resin, and then
placed in a UV oven for a final curing. The model is then finished
by smoothing the "stair-steps."
Materials
The
materials used by SLA equipment are epoxy-based resins that offer
strong, durable, and accurate models. It is ideal for form, fit,
and function testing as well as for visual aids and patterns for
tooling. In many cases, SLA is capable of reproducing snap fits.
In general SLA materials have a low heat tolerance with typical
heat deflection temperatures are around 110-120�F. Standard tolerances
are � 0.005" on most parts and features. These characteristics
make SLA an excellent all-round choice for prototypes.
SLA
Material Properties Available
Mechanical
Properties
|
Test Method
|
Units
|
Rigid
(SL5195)
|
Durable
(SL 7540)
|
Flexible
(Somos 8100)
|
|
Tensile Strength
|
ASTM D638
|
psi
|
6,740
|
5,500
|
3,800
|
|
Tensile Modulus
|
ASTM D638
|
psi
|
303,000
|
223,000
|
73,500
|
Tensile Elongation
at Break
|
ASTM D638
|
|
11-22%
|
22%
|
17-24%
|
Flexural Strength
|
ASTM D790
|
psi
|
7,150
|
7,000
|
3,700
|
Flexural Modulus
|
ASTM D790
|
psi
|
236,000
|
199,000
|
91,000
|
Hardness
|
DIN 53505/2240
|
Shore D
|
83
|
79
|
81
|
Izod Impact - Notched
|
ASTM D256
|
(ft-lb)/in
|
1
|
0.72
|
1.1
|
Heat Deflection Temp
|
ASTM D648
|
Deg F
|
117
|
135
|
130
|
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