Development and Testing of a High-Frequency Dynamometer for High-Speed Milling Process

Abstract

Cutting forces are strongly associated with the mechanics of the cutting process. Hence, machining forces measurements are very important to investigate the machining process, and numerous methods of cutting forces measurements have been applied. Nowadays, a dynamometer is the most popular tool for cutting forces measurements. However, the natural frequency of a dynamometer has a direct impact on the accuracy of measured cutting forces in the machining process. Therefore, few dynamometers are appropriate and reliable to measure the cutting forces at high frequencies. In this work, a new strain-gauge-based dynamometer (SGBD) with a special structure was designed, manufactured, and put to the test to ensure the measurement of high-frequency dynamic forces in the milling process. The main structure of the SGBD is symmetrical and mainly consists of a center quadrangular prism surrounded by four force sensing elastic elements, an upper support plate, and a lower support plate. The dynamic identification test was conducted and indicated that the SGBD′s natural frequency could be stabilized at a high value of 9.15 kHz. To automatically obtain the milling force data with a computer during high rotational speed milling, a data acquisition system was devised for the dynamometer. To reduce the effects of cross-sensitivity and acting point of force, an innovative model based on a conversion matrix was established for the dynamometer. Furthermore, the cutting tests were conducted at high rotational speeds (10,000–18,000 rpm), and it was found that the difference of cutting forces between the SGBD and a Kistler dynamometer are 2.3–5.8% in the X direction and 3.5–8.8% in the Y direction. The experimental findings disclosed that the new kind of dynamometer is reliably for the measurement of high-frequency dynamic forces in milling at high rotational speeds.