On-Line Process Control in Melt Spraying Using Phase - Doppler Anemometry

Phase Doppler anemometry (PDA) and Extended phase Doppler anemometry (EPDA) are used for the characterization of powders produced with different melt atomization techniques. A laboratory scale production type melt spray facility was adapted for the application of PDA and measurements were performed in conventional gas atomization (CGA) of melts. In liquid gas atomization (LGA) of melts an extended phase Doppler system has been used allowing a distinction between melt particles and liquefied gas droplets. In CGA, the results obtained with PDA show some discrepancies with off-line powder characterization techniques, however, variations of process conditions leading to changes in the powder size distributions could be successfully detected. Hence, a first attempt is presented how phase-Doppler anemometry can be incorporated in a process control loop. In LGA, liquefied gas droplets and melt droplets could be successfully discriminated by using a sign of phase EPDA system. However, additional measurements are necessary to improve the reproducibility of the results.