ON-MACHINE POSITIONING METHOD FOR INTEGRAL IMPELLERS BASED ON THREE-DIMENSIONAL POINT CLOUD

The integral impellers are crucial components of aerospace engines. In recent years, pre-formed blanks made through 3D (three-dimensional) printing and powder metallurgy have been increasingly used to improve material removal rate and processing efficiency. However, advanced blank manufacturing processes require higher precision in clamping alignment. The 3D camera system is poised to replace on-machine probes in achieving precise pose of blanks as they provide measurements with high accuracy and density. In this paper, we propose a methodology for precisely determining the positioning and pose of integral impeller blanks based on 3D point clouds. We first calibrated the 3D camera on the CNC machine. The homogeneous transformation matrix of the 3D camera coordinate system relative to the CNC machine coordinate system was calculated. Then, our proposed method enables a rapid alignment of the point clouds obtained from the blank with the corresponding CAD model. Finally, the machining allowance at the blades on the blank is calculated and optimized. Our on-machine 3D camera system has been successfully implemented on a CNC machine, and our proposed method has been validated. The system reduces measurement time by 5/6 compared to contact probes, making it highly efficient. The average machining allowance distribution was adjusted from 2.55 similar to 3.56 mm before optimization to 2.92 similar to 3.22 mm after optimization. On-machine measurement experiments with the contact probe have also verified that compensation is effective. The system is expected to be extended to other complex-shaped parts such as inlets for clamping processes.