Post-machining allowance optimization of directed energy deposited impeller blades using point cloud registration

Complex free-form parts manufactured by directed energy deposition (DED) have problems of uneven allowance distributions and severe stair-case effects. In order to optimize allowance for post-machining in a hybrid additive and subtractive machine centre, a point cloud registration method is proposed for allowance optimization to match the on-machine measured point cloud of the deposited part with the point cloud of the theoretical model. Firstly, the deposition path is used to construct the inspection path and obtain the maximum and minimum envelops of the deposited part. Secondly, the allowance distribution for the uniform and positive criterion is solved using the pattern search algorithm, after the datum planes are overlapped. Finally, a free-form blade of a centrifugal impeller is selected as a case study for allowance optimization. The proposed method is also compared with an allowance optimization method using genetic algorithm. The results show that the proposed method is more accurate and efficient for rapid allowance optimization for DED complex parts.