Research On Spindle Electro-hydraulic Servo Loading Reliability Test Technology Based On Load Spectrum

As the complex CNC machining equipment, machining centers is widely used in various manufacturing and processing industries. Due to the lack of scientific and rational load spectrum which is used for guiding machining centers’reliability probabilistic design, selection of parts and reliability test, the reliability level of domestic machining center is generally low. As the key function units of Machining centers. The spindle directly affects the overall reliability level of machining centers. Therefore, compiling the scientific and reasonable load spectrum for Machining centers have great significance to guide the spindles’ reliability test.The article is researched basing on the national major science and technology subject "High-grade CNC Machine Tools and Basic Manufacturing Equipment " and Jilin Province science and technology agency "Characteristic Industry Base Construction Projects". System modeling is built and the dynamic characteristics is analysed for spindle Electro-hydraulic servo loading reliability test bed, what’s more, the load spectrum compiling method of domestic machining centers is discussed, which is used for the reliability test of the machining centers’ spindles.The main research tasks of this article are as follows:1. Establishing electro-hydraulic servo loading system model based on the spindle reliability test bed. Besides, dispersing the model and deducing the discrete model of the system. Then assessing the discrete model parameters by using the least squares algorithm and obtaining the maximum load frequency through Bode diagram.2. The orthogonal design experiment of cutting load is carried on based on the cutting load data of Machining center. and can represent the real working conditions of cutting load data, and then on the cutting load data preprocessing and fast Fourier transform, and by using multiple linear regression analysis method to get the each order dynamic force of linear regression relationship between frequency and spindle speed.3. On the cutting load signal spectra pretreatment, using the decomposition synthesis method to reconstruct the radial force of the time-domain signal, and give full consideration to the effects of various cutting section cutting load, the load of the test section processing, complete cutting load sample data are obtained.4. From the angle of time domain, the rain flow count method was used to sample data of cutting load statistical count, and according to the load-percentage frequency histogram characteristics determine the alternative probability density distribution model, then using local optimal particle swarm optimization algorithm and kohl alamogordo rove test alternative distribution model for the parameter estimation and test of goodness of fit, and obtains the optimal cutting load, the amplitude distribution model and amplitude two-dimensional joint distribution model, namely the radial force amplitude spectrum and the mean value and mean amplitude of two-dimensional spectrum; Axial force amplitude spectrum and the mean value and mean amplitude of two-dimensional spectrum; Cutting torque amplitude spectrum and the mean value and mean amplitude of two-dimensional spectrum. By step speed and work in factory to collect data for statistical time, obtained the data of the spindle rotating speed spectrum. And stack for each order dynamic power frequency to synthesis, from the point of view of frequency domain dynamic force frequency spectrum.5. By using the method of Monte Carlo Simulation, the mean time between failtures (referred to as MTBF) of the spindle subsystems is calculated, and the spindle reliability test time is determined from the Angle of MTBF. Then, the spindle reliability test preparation is put forword and the load spectrum is adapted.the reliability test scheme is determined based on program load spectrum.