Identification of dynamic process response in DED-type additive manufacturing process and its application to process optimization

Abstract

For aiming at successful operation of directed energy deposition (DED) type additive manufacturing (AM) system, three different kinds of process elements, machine motion, powder supply and laser application, needs to be synchronously controlled for accurate shape creation of the work piece. In order to synchronize these elements, in this study, measurement method of these response delay time has been proposed. According to the method, using the specific DED type AM system, the response delay time has been identified as that of laser application is 0.72 ±0.2 second and the powder supply control has about 15 seconds response time delay while the evaluated response delay time of nozzle motion was negligible compared to that of other two elements. Using identified response characteristics, dead time compensation control has been adopted to absorb the response delay time of laser and powder application processes. Laser application commands were indicated prior to reaching targeted positions and a pseudo motion command was inserted to absorb the response delay time of powder supply before starting the subsequent actual deposition with the correct powder supplied amount. Performing experimental studies, target deposition shapes have been achieved without unintended deposition and effectiveness of the proposed optimization method has been confirmed.