A novel force-based two-dimensional tool centre error identification method in single-point diamond turning

Abstract In single-point diamond turning (SPDT), two-dimensional (2D) tool centre error is caused by the tool deviating from the workpiece rotation centre both in the horizontal direction (tool feed direction) and vertical direction (perpendicular to tool feed direction). This greatly affects the form accuracy of the machined surface and its optical function. Traditional tool centre error identification is usually performed off-machine manually with high-precision instruments, which is time-consuming and labour-dependent. In this paper, a novel force-based 2D tool centre error identification method in SPDT is introduced. First, according to the relative position between the tool and workpiece centre, the tool centre error is classified into nine cases. The relation between the cutting force profiles and the tool centre error is analysed for each case. Then, a numerical fitting model and a geometric model are established to identify tool-above-centre and tool-below-centre errors, respectively. Additionally, a geometric model is established to calculate the normal distance from the tool interference/exit cutting to the workpiece centre, which serves as a reference for the horizontal tool centre error identification. Finally, the on-machine identification results of the 2D tool centre error are verified by experiments. Theoretical and experimental results show that the proposed on-machine 2D tool centre error identification method is effective and accurate, which greatly improves the cutting efficiency in SPDT.