Validation of spatial accuracy with high-speed imaging to support <i>in situ</i> flaw detection for laser directed energy deposition processes

The application of in situ monitoring systems for part quality verification or process qualification of the laser based directed energy deposition process will require the ability to confidently detect (or estimate) the type, size, and location of defects in an additive manufactured component. These developments are requested by the industry to supplement the expensive and time-consuming ex situ inspections for part certification to further support the number of viable business cases. This confidence level of the in situ monitoring solutions should be comparable to that of the ex situ inspection techniques (such as microcomputed tomography). These developments will also require very large experimental data sets with spatially resolved in situ monitoring signals which must be correlated to ex situ inspection data. A crucial element in this correlation is the spatial absolute accuracy of these signals from both in situ and ex situ solutions. The in situ solutions should, preferably, at least match with ex situ accuracy. Currently, there is no consensus framework for validation of the spatial accuracy of the in situ monitoring signals. Therefore, a method will be presented in this paper to evaluate the spatial accuracy obtainable with the typical available location information on ethernet field bus implemented in the laser based directed energy deposition process. The accuracy is verified by the implementation of a high-speed imaging setup that additionally enables to verify the synchronization accuracy of the imaging solutions. Cameras act often as a source of data for the in situ monitoring solutions of the melt pool.