Compilation of Program Loading Spectrum for CNC Lathe’s Feed System Based on Two-dimensional Kernel Function

Program loading spectrum is a prerequisite for carrying out reliability test, and it is also an objective basis for reliability design. In the actual cutting process, the Computer numerical control (CNC) lathe's feed system mainly bears both the feed speed and the friction load. Therefore, this paper establishes a two-dimensional program loading spectrum of reliability test for CNC lathe's feed system based on two-dimensional kernel function. First, the relationship between the frictional force in each feeding direction for CNC lathe and the three-axis cutting force is determined. Second, the kernel function is used to fit the load distribution in each feeding direction for CNC lathe, and the maximum likelihood estimation method is used to estimate the function parameters. Thirdly, the expansion factor method is used to extrapolate the load spectrum, and the load spectrum is divided into 8 levels. Finally, the loading spectrum in different feed directions for CNC lathe is compiled. In this paper, the loading spectrum and corresponding relative friction force of the HTC 40100 CNC lathe is established. This two-dimensional program loading spectrum can be applied to the reliability test and life prediction of feed system, which has important engineering application value.