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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 compensation 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 effective 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. [ABSTRACT FROM AUTHOR]

Chatter vibrations in machining have collected the interest of several research activities in the last decades, mainly due to its detrimental effect on productivity and surface quality. Several approaches and techniques have been developed to mitigate the effect of these unstable vibrations, but the required expertise and setup time usually prevent the widespread industrial application. Retrofittable intelligent active fixtures, capable of monitoring the process in real-time and exert adequate counter-excitations, could allow to overcome some of these limitations. Nevertheless, the use of these devices was always limited to the mitigation of structural chatter vibrations, which are the ones generally fitting in the device bandwidth. This paper deals with the development of an active fixture using an alternative control strategy that exploits low-frequency excitations, with the purpose of mitigating the chatter vibrations at frequencies exceeding the device bandwidth. The paper covers the main aspects of the fixture design and mainly focuses on the theoretical and practical aspects of the followed approach for the control. An experimental tests campaign is finally discussed to show that the proposed approach is actually effective in mitigating chatter vibrations. [ABSTRACT FROM AUTHOR]