WHAT IS SLS (‘SELECTIVE LASER SINTERING’)

SLS is a 3D Printing technology similar to SLA where a CO2 laser is fusing or sintering a powdered material together via a highly accurate computer controlled laser and mirror system. Selective Laser Sintering is a fast and accurate prototyping technology producing durable parts quickly and cheaply.

Using a laser, which is very directive and focalized (hence accurate to reach a target) as the power source to sinter powdered material it binds the material together to create a solid structure. It is a convenient as well as a cost-effective way to make prototypes as well as finished products. The parts need little post process finishing and are suitable for a wide range of applications.

WHY USE SLS FOR RAPID PROTOTYPING

If the part you need to make are high complex in terms of shape, then there is high chance you may not be able to use the CNC process to make it. On this base you may need to use another process of rapid prototyping where the part is made by piling layer after layer of material. The process is similar to what a 3D printer do, but the SLS process allow to have different type of material and is much more accurate than a 3D printer.

PROCESS OF RAPID PROTOTYPING WITH SLS

SLS machine functioning is actually quite simple: the surface of a vat of liquid is scanned by laser which fuse very locally some dot on the surface of the liquid producing a solidified part. The laser scan in 2 dimensions the liquid surface and generate a layer of solidifed part. This solidified part is handle by a fixture who layer after layer step down of a distance equivalent to the resolution of the machine. Once a layer is over, the fixture go down one step and another layer is created while adhering to the previous one.

Layer after layer, the part is created in 3 dimensions.

As the machine is controled by a computer and since it control the path of the laser at the surface of the liquid according to two axes, we first need to generate a file which indicate to the laser on which X, Z coordinate the laser should fuse the liquid. Hence, we need to feed it with a special file generated from a particular software which cut in slice / layer the object which need to be generated.

Once done, the process can start and the part can be generated step by step and layer by layer, one layer getting sintered to the previous one

At the end of the process the full part is generated and quite often a finishing has to be done by performing a very slight polishing to smooth the surface.

ADAVANTAGES OF SLS FOR RAPID PROTOTYPING

– High precision: Tolerances of +/-0.1 mm
– No important labor requirement so can lead times can very fast. Lead times as short as 1 day until ready to ship (depending on the finish requirements)
– Complex parts can be produced that are not possible to machine without joining or generated from CNC process
– Wide range of resins available

LIMITATIONS OF SLS FOR RAPID PROTOTYPING

The materials are not as representative of the reality as they would be if you use CNC machining.

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