In-Process Control of Selective Laser Melting by Quantitative Optical Tomography

Selective laser melting is a promising technology for additive manufacturing of complex shaped parts. The technique uses metallic powder as starting material and a laser for melting and building-up parts layer by layer. During build-up small defects can arise, impossible to detect by non-destructive testin g after the SLM-process, but having strong impact on the quality of the SLM-parts. Therefore, in addition to standard non-destructive inspection techniques, a new inprocess monitoring tool was developed and integrated into SLM machines: the optical tomography (OT). By using x-ray micro focus tomography on specially prepared samples OT-indications could be correlated to real defect sizes. Together with statistical evaluation of the OT-indications the optical tomography has evolv ed from an in-process monitoring tool into a powerful in-process contro l tool.