Influence of thermal deformation of drilling machine on hole registration accuracy

Purpose: The purpose of this study was to investigate the thermal deformation effect of a machine tool frame on hole registration accuracy. Hole registration accuracy represents the drilling performance of a machine tool, and it greatly depends on the thermal deformation of the machine frame structures in practical engineering. Reducing thermally induced errors is crucial to improve the hole quality. Design/methodology/approach: First, the thermal design of the machine frame was performed via an optimization procedure to reduce the thermal deformation at an early stage. Then, a thermal-mechanical coupling finite element method model was established to quantify the thermal deformation of the machine tool under environmental temperature fluctuations, and the validity of the presented model was confirmed experimentally using laser interferometry. Finally, a series of drilling tests, including micro-holes and medium holes, was carried out to practically investigate the hole drilling registration accuracy of the machine with a mineral casting frame under different thermal conditions. Findings: Hole registration accuracy showed positional dependency and distinctly non-linear behaviour at different drilling axes which was closely related with the thermal conditions. The positional deviations of medium holes and micro-holes all showed an increasing trend in different degrees under the same temperature fluctuations, and the former were more sensitive to the latter. Therefore, keeping the drilling workshop under thermally stable conditions is crucial for improving the drilling performance of the machine. Originality/value: The goal of this paper is to reveal the mechanism of hole registration accuracy variations with thermal fluctuations and to provide a strategy for the machine tool industry to further improve the drilling performance during the machining process