Selective Laser Sintering, SLS

Selective Laser Sintering (SLS) is a well-developed additive manufacturing process that can be successfully used for both prototyping and manufacturing applications. The process works in a similar way to the stereolithography (SL) process in that an Argon laser is used to create a 3D part, layer-by-layer, by tracing the required shape direct from a 3D CAD model via a .stl file. Where SLS is very different from SL is in the format of the materials used and the reaction of the laser with these materials. Selective laser sintering processes finely powdered materials that are tightly compacted and housed in a powder bed within the machine. As the laser interacts with the powder it is fused — or sintered — to form the selected shape and as each layer is completed the powder bed drops down fractionally so the next layer can be traced, sintered and bonded to the previous layer.

The powder bed provides any necessary support for the parts that are being built, negating the requirement for any additional supports to be built into the design — a favourable difference from stereolithography. Once the part is complete, it is raised out of the powder bed and any excess powder can simply be removed by brushing it away. A distinct advantage of this process is that because it is fully self-supporting, it allows for parts to be built within other parts — with highly complex geometry that simply could not be made any other way. Another key advantage of this technique is the durability and strength of the materials and in addition SLS produces a product that requires no post curing.

Like any manufacturing technique however, it is not perfect. One of the disadvantages of the SLS process is that it can result in parts that are porous, and for certain applications, this may necessitate the part being infiltrated to improve certain properties of the material. However, it should be stated here, that with Ogle’s EOS machines only the surface of SLS parts are porous and therefore, there is no requirement for infiltration. A specific application that illustrates this point extremely well comes in the form of a brief given to Ogle to produce a series of liquid containers — Ogle built the containers using the SLS process and they all performed perfectly, with no extra post process required. Also, the surface finish and accuracy of SLS are not of as high a standard as with SL.

The team at Ogle is fully experienced with the selective laser sintering process for plastic materials and can offer comprehensive advice to clients to enable them to realize the process’ full potential — both for prototyping applications and manufacturing/production applications.

In house SLS machines at Ogle:

EOS P100
EOS P385
EOS P730

SLS Materials used in house at Ogle:

Glass Filled Polyamide
PA2200 nylon
Polyamide 2210 FR

For the full range of in-house modelling and prototype equipment across all processes, click here.