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The delivery of powder to the melt pool via the nozzle is a crucial element at laser material deposition. It has a major influence on the consumption of powder material and the quality of the coating layer. In order to ensure consistently high process stability and quality, it is necessary to check the powder gas stream at regular intervals. In considering a powder gas stream, the important variables that need to be monitored includes the symmetry of the powder gas stream and the position and size of the powder focus. In order to measure the requisite variables, the powder gas stream is illuminated from the side using a laser line and monitored by a coaxially aligned camera through the powder nozzle. A high image rate allows the number and position of individual powder particles to be recorded. Relevant algorithms are used to calculate the particle density distribution from these images. The spatial particle density distribution of the powder gas stream can be calculated by superimposing individual levels along the powder gas stream. The measurement principle was successfully tested on various powder nozzles. The measurement process makes it possible to fully characterize a powder gas stream.
Mann et al. (Tue,) studied this question.