Diametral error correction in turning slender workpieces: an integrated approach

Turning slender components is a critical task since workpiece flexibility entails relevant deformations during the process, leading to potential loss of accuracy, lower machining efficiency, and higher manufacturing costs. In this paper, a compen- sation strategy for diametral error in turning of slender workpieces is presented. The proposed method computes a toolpath that compensate diametral error based on the prediction of such error performed by a finite element-based approach. The developed algorithm automatically generates the compensated toolpath based on few inputs: nominal toolpath, workpiece material, tool geometry, stock dimensions, and fixturing system. First, nominal toolpath is analyzed and discretized, then at each step, workpiece deflection is estimated by coupling the FE model of the workpiece (automatically generated using Timoshenko beam elements) and the cutting forces model. Material removal is considered in the process by updating the geometry of the stock at each step of the machining cycle. Using the predicted deformation of the workpiece the compensated toolpath is generated and the toolpath ISO-standard file is updated. The proposed algorithm was experimentally validated on four case studies: three single diameter bars and a multi-diameter shaft. The results demonstrate the accuracy of the proposed predictive approach, with small deviations in estimating average diametral error (less than 6 μm). Furthermore, it has been demonstrated that the compensated toolpath is successful in reducing the diametral errors by at least 50%, as well as smoothing the error shape, confirming that providing an accurate prediction of the shape error could represent an effec- tive approach for its reduction. The proposed methodology could form the basis of a toolpath simulation and optimization software, useful for machining shops that deals with slender shafts turning.