Adaptive hybrid control for the formed morphology in powder-based laser metal deposition

The application of powder-based laser metal deposition in the field of industrial production has been limited for the formed geometrical morphology and mechanical performance of additive manufacturing parts. Process variable monitoring and feedback control of the deposition process is an effective method to improve the dimensional accuracy of the manufactured part. In this study, distinguished from the earlier research on processing technology of objects with a small size and a simple structure, an adaptive hybrid control method was proposed for the parts that were relatively complex in structures and required a long period of multilayer deposition. First, laser power was dynamically adjusted in real time based on the adaptive fuzzy proportional integral control algorithm to maintain the stability of each deposited layer through the monitoring of the molten pool temperature. Then, the deposited height was collected in stages and a compensation control method for the adjustment of powder feeding rate was developed. Finally, the hybrid control method was verified through the manufacture of a typical thin wall U-shaped part made of Ti6Al4V. Results show that compared to the open-loop process, deposited height deviation and the wall thickness deviation of the U-shaped part are reduced by 94.36% and 98.95%, respectively, and the surface quality is effectively improved with the value of the surface roughness (root mean square height, Sq) reduced by 70.68%. In addition, a maximum overlap volume ratio of 91.77% between the deposited model and the designed geometrical model was obtained.