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New sensor and system technology for higher process stability in LMD

In Laser Material Deposition (LMD), the powder feed into the melt pool is of crucial importance. It has a decisive influence on powder efficiency, geometry and roughness of the layer generated and oxidation by the surrounding atmosphere. For this reason, there is a need to characterize the powder gas jet to ensure process quality. As a solution a machine integrated system was developed, that has the capability to document the particle density distribution. For standardized measurements and comparability of results the procedure is fully automated. In order to measure and capture the required parameters, the powder gas jet is illuminated by a laser line perpendicular to the powder gas stream and observed through the powder nozzle with a coaxially arranged camera. A high frame rate allows the individual powder particles to be captured in number and position. Through step-by-step movement along the powder gas stream, individual layers are recorded in order to reach the particle density distribution with corresponding algorithms. From this distribution, key figures, e.g. position and diameter of the powder focus, can be derived for certification of powder feed nozzles. This information allows the adjustment and wear state of a nozzle to be documented and the processes to be set-up reproducibly. Furthermore the system is used to study the parameters influencing the shape of the powder gas jet. This knowledge can be used for process development, nozzle development and for the production of components with high requirements upon quality.