A Technique for Integrated Compensation of Geometric Errors and Thermal Errors to Improve Positional Accuracy of Hole Machining in Large-Size Parts

Abstract

Large-size parts such as aircraft wing structures require a lot of hole machining for assembly between parts. As demand for hole positional accuracy, such as in determinant assembly (DA) concept, securing the positional accuracy of hole machining is becoming more important. Specifically, during the hole machining of large-size parts, significant errors occur due to thermal expansion according to temperature change of a machine tool and a workpiece. In this study, a technique for efficiently reducing the positional error of hole machining in large-size parts is proposed by compensating geometric errors and thermal errors of a machine tool and a workpiece. The thermal displacement error, representing changes in volume error due to temperature variations in the machine tool, is estimated by measuring the distance between the centers of two spheres on the master with low thermal expansion coefficient measured at the reference temperature (20 °C). The thermal expansion error, caused by variations in workpiece temperature, is estimated by assuming the temperature of the workpiece to be that of the cutting fluid just before machining. Hole machining errors are integrally compensated by considering the geometric error measured at the reference temperature and the thermal errors of the machine tool and the workpiece. In the verification experiment, the maximum error was improved by 60.2%, and it was confirmed that the tendency of the error was significantly reduced.