The Characterization of the Performance of a New Powder Feeder for Laser Based Additive Manufacturing

Laser-based additive manufacturing (LBAM) requires precise control over the metal, ceramic, or carbide powder added to the molten pool. The feeding rate of the powder must be very consistent, and it must respond rapidly to commands to change the feeding rate. LBAM also requires feeding rates as low as one gram per minute. Currently, commercially available powder feeders are optimized for such tasks as feeding powder to thermal spraying processes, which generally require a much higher feeding rate than LBAM, and can usually tolerate much more variation in the feeding rate. These powder feeders are therefore not suitable for the LBAM process. The Research Center for Advanced Manufacturing at Southern Methodist University has designed and built a new powder feeder capable of consistent, repeatable powder delivery at extremely small flow rates. The powder feeder is regulated by a weight-based control system, which provides real-time measurement of the mass remaining in the feeder as powder is transferred to the powder nozzles. The powder feeder has been fully characterized to obtain correlations between the input parameters, powder type and the resulting mass flow rates. The powder nozzles at the laser head have also been characterized. The nozzle angle, standoff height, and carrier gas flow rate have each been optimized experimentally to maximize the concentration of powder arriving at the molten pool created by the laser beam, as detected using a sheet of He-Ne laser light and a coaxial vision system. The powder delivery efficiency of the system has been thus maximized, increasing both the deposition rate and the quality of the deposited material.