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Post-Processing of additively manufactured polymer parts

on Aug. 14, 2019
The Post-Processing of laser sintered parts is a crucial step in the additive process chain. It highly depends on the clients’ wishes concerning the part surface, mechanical properties or the part color.

Laser sintering technology is a manufacturing process that enables the layer-by-layer production of components from powdered plastics directly from 3D CAD data. Highly complex plastic components with a high degree of functional integration are possible without shaping tools or support structures. Depending on the customer's requirements regarding the component surface, the mechanical properties or the color of the component, it may be necessary to rework the additively produced components. These steps are called post-processing and directly follow the successfully completed construction process.

First, the components are separated from the non-sintered residual powder (cake). In order to remove strongly adhering residual particles from the surface, each component is blasted with glass beads in a blasting system and cleaned of any blasting material residues using compressed air. After the complete cleaning of the components, an initial visual evaluation of the component quality (including surface roughness, wall thicknesses and possible component defects) is carried out.

The painting of the component surface is suitable for improving the surface quality. For this process, the component must first be primed or filled. This is followed by intensive sanding of the filling layer produced in this way with subsequent cleaning of any dust and sanding residues. Last but not least, the coating is carried out with 1K or 2K lacquers. It is also possible to use special varnishes which, for example, have conductive properties. Depending on the geometry of the component, possible internal surfaces during component design, which can only be treated to a limited extent in the subsequent process, must be considered.

If the customer requires improved chemical resistance, air-, gas- or liquid-sealed components, an infiltration process follows the component cleaning. Infiltration closes the pores of the material by dipping, spraying or brushing with an epoxy. The infiltration process does not significantly alter the final dimensions of the additive component, so that the narrow tolerances achieved in the additive process are not affected negatively.

Other post-processing steps include component coloring, vibratory finishing to optimize surface roughness, and component coating with metallic coatings to improve mechanical component properties.