With SLS, just like with any other 3D printing technique, the model is built layer by layer. However, different from FDM, with SLS the model is made using a powder bed.
A so-called recoater deposits a thin layer of powder on the building platform. This layer is heated and a laser scans the shape of the model, thus melting the powder and forming a layer of the product. The recoater then deposits another layer and the whole process is repeated until the part is built up.
With the SLS technique we work with Nylon (PA12). This material is characterised by a relative high strength and flexibility. SLS has a standard layering of 0,1 mm per layer and due to its mat finish the products show less visible layering than with FDM.