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SLS® Process
Simple
Explanation
Selective Laser Sintering
(SLS) is a powder based Rapid Prototyping method. The technique,
shown in Figure 1, uses a laser beam to selectively fuse powdered
materials, such as nylon, elastomer, and metal, into a solid
object. Parts are built upon a platform which sits just below
the surface in a bin of the heat-fusable powder. A laser traces
the pattern of the first layer, sintering it together. The platform
is lowered by the height of the next layer and powder is reapplied.
This process continues until the part is complete. Excess powder
in each layer helps to support the part during the build.
Figure 1: Schematic diagram of the selective laser sintering
SLS® Process.
Detailed
Explanation
Selective
Laser Sintering (SLS) is a powder based Rapid Prototyping method.
The process uses a layer system of building up a part with each
layer of powder being sintered seperately by a laser. As each
layer is sintered it slowly constructs the part step by step.
There are various grades of materials used each with there own
characteristics but each are used the same way within the SLS
machine.
The SLS machine basically consists of 3 Powder beds and a Laser.
Two of the powder beds hold the feed powder and the third bed
holds the part. The part bed is middle of the beds with the
laser acting directly perpendicular to this bed. A roller is
used to push the layers of powder over the part bed and all
three beds have their own heater source. The process itself
is a very simple repeatable one.
The building of the parts is a repeatable two step process.
Step 1
A roller is positioned beside one of the feed
beds. This feed bed then raises a set amount (Usually < 0.1mm)
and the roller pushes the raised powder across, covering the
part bed with a Powder Layer.
Step 2
With the layer of powder present the laser starts
to etch out the desired shape of the part in the powder in effect
melting the powder. Once this is done the part bed drops down
the set amount and the process continues from the opposite side
with the other feed bed raising and the roller distributing
another layer of powder over the part bed and the laser etches
out the shape.
The part
is built up in slices with each layer of powder representing
a single slice of the part. As the laser melts/sinters the
powder each layer fuses together to give a full solid part.
Because of the fact that the part is made up in slices very
complex shapes and designed can be manufactured that would
otherwise be impossible by conventional means.
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