Compilation Method And Application Of Load Spectrum Of A Medium Type Full Function General Horizontal CNC Lathes

Load spectrum is a prerequisite to solve the problem of longevity, life-prolonging and life-cycle initiative reliability to mechanical structures. Differences between the load spectrum of Computerized Numerical Control (CNC) lathes and mechanical structures are obvious because of the instability of the load time history of CNC lathes. In order to establish scientific and reasonable references for the reliability design and test of overall unit of CNC lathe and its key features (main shaft system, feeding system, etc.),four types of load spectrum of spindle and feeding system have been built in this paper on basis of site load data acquisition and combination with previous research findings. In addition, the method for determining of the sampling time for setting up the load spectrum of CNC lathe,which has not been discussed in previous research, was proposed preliminarily in the end of this paper.The specific contents and main conclusions of this paper are as follows:1. Combined with fatigue load spectrum compiling process of mechanical structures, this paper has put forward six principles-directionality, typicality, comprehensiveness, authenticity, practicability and economy, for the standardization of the establishment of CNC lathe load spectrum.2. With reference to previous research results, the CNC lathe load data collection process, the cutting force values of data acquisition technique, load data statistical process were described in detail.3. Simulated Annealing Optimization algorithm was applied to estimate the unknown parameters of the six kinds of classical statistical distribution engaged for fitting of the load data. Cole Alamogordo Rove Test method has been used to judge the fitting effects of the mentioned statistical distribution models. Using Parzen kernel density estimation method combined with "Delta Area" algorithm to optimize one single distribution model which was best fitting the load data, the conclusions are as follows:a. The relative cutting torque of this batch of CNC lathes obeys Gamma distribution with the shape parameter α=0.4591and the scale parameter β=0.3468, namely b. The relative feed force of this batch of CNC lathes obeys Logarithmic normal distribution with the mean value μ=-3.2761and the standard deviation σ=0.3988, namelyc. The relative cutting-in resistance force of this batch of CNC lathes obeys Normal distribution with the mean value μ=0.0125and the standard deviation σ=0.0309, namelyd. The relative spindle speed of this batch of CNC lathes obeys Logarithmic normal distribution with the mean value μ=-2.0241and the standard deviation σ=0.5861, namely4. Taking the load performance test of CNC lathe spindle system for instance, the relative load spectrums were applied to the load performance test of key features of CNC lathe. MATLAB Graphical User Interface (GUI) was applied to compile CNC lathe spindle torque load test spectrum generator (LSLT) software in this paper, which was based on the actual working condition and empirical data, and was able to generate CNC lathe spindle torque-load schedule automatically according to the main shaft relative cutting torque load spectrum.5. The method for determining of the sampling time for setting up the load spectrum of CNC lathe,which has not been discussed in previous research, was proposed preliminarily in the end of this paper.