Towards in-situ process monitoring in selective laser sintering using optical coherence tomography

Selective laser sintering (SLS) enables fast, flexible and cost-efficient production of parts directly from 3D CAD data. However, compared with more established machine tools, there is a marked lack of process monitoring and feedback control of key process variables to optimize production parameters in-situ. We apply optical coherence tomography (OCT) to evaluate components produced by SLS and suggest a route for its application in in-situ process monitoring within the SLS tool for real-time monitoring of the SLS process for assurance, or even dynamic correction of defects during the build. OCT is shown to be a viable technique for evaluation of both surface and sub-surface features built into a part either by design or from poor sintering or non-homogeneous powder spreading. We demonstrate detection and quantification of surface defects on a ~30 μm scale in a Polyamide (PA2200) part, resolving ‘built-in’ fine features within a 200 to 400μm depth below the surface.