The Study Of Reliability And Optimization Of High-speed Vertical Machining Center Feed System

As the foundation industry of manufacturing, high-speed vertical machiningcenter has become one of high-tech development directions of the manufacturing.Improving the performance of the machining center not only requires theprocessing center with good dynamic and static performance, but also with highreliability protection to length work cycle in high efficiency. So, it has become anecessary part of design research for high-speed machining centers to analyzetheir static&dynamic performance and reliability. Processing center feed systemis the key parts of the machine, so it can affect the processing performance of theentire machine directly. Research of this subject can improve the reliability andanti-resonance of the feed system performance at the maximal degree, and alsoprovide technical support for analyzing performances of other parts of themachining centers and the entire machine.Structural reliability and optimization research of machine tools andengineering application have been obtained a lot of progress at home, but thereare still many theoretical and technical issues need to resolved in structureanalysis, anti-resonant reliability and optimization of the processing center feedsystem.Combined with national projects，this paper took DVG850high-speedvertical machining center feed system as the research object to carry out thefinite element analysis, the anti-resonance reliability analysis and optimization.Based on the collected the actual fault data in using machining center of someenterprises, that the feed system is one of the main parts to cause the failure ofmachining center was got by analysis, among which that the machining accuracyoversize was the main factor to cause the failure of machining center. And inprocessing of machine, vibration caused by the resonant was one of the mainfactors of the machining accuracy oversize.For the weak link of machining center feed system and its failure reason, according to the design experience of machining center and combining with theactual processing condition of DVG850high-speed vertical machining centerspindle speed, taking the X axis direction as the example, four structure typeshigh-speed vertical machining center feed system model including nets stiffenerstructure、straight stiffener structure、inclined stiffener structure and inclinedround stiffener structure, were designed. Based on ANSYS Workbench12.0software platform, the static characteristic analysis on the four structure feedsystem model was made. The deformation of the four model structure feedsystem’s directions was carried out by analysis, four feed system static stiffnesswas calculated out, the comparative analysis on all directions was made and theoptimal model was selected. The results show that, in machining center Xdirection feed system, the static stiffness value of nets stiffener structure feedsystem model was max.The probabilistic design of reliability on the high-speed vertical machiningcenter feed system model of four structure type including nets stiffenerstructure、straight stiffener structure、inclined stiffener structure and inclinedround stiffener structure was made, and the first8-order natural frequency andthe corresponding vibrating mode graphics were got, after analysis, theconclusion that the natural frequency value of the nets stiffener structure feedsystem first three-order was the highest. We adopted fuzzy reliability theory toestablish membership function, applied the APDL language programming byfunction fuzzy membership function in reliability analysis to sample afterextracting the modal frequencies, and four structure feed system model’s fuzzyreliability of anti-resonance was calculated, after analysis, the conclusion thatfour structural type model’s fuzzy reliability the largest was the nets stiffenerstructure feed system which was98%, was got; after comprehensive analysis,that the nets stiffener structure feed system’ static characteristics and reliability ofanti-resonance than other three structure types even better was carried out.According with topology optimization theory, the high-speed verticalmachining center feed system optimal model of the nets stiffener structure feedsystem was carried topology optimization. In order to improve the anti-resonancereliability of the feed system, the Weighing Average Function of the first threeorders’ natural frequency was set of the objective function of optimization and the volume as constraint function. According to the topology pseudo-densitycloud images and assembly size in processing, we improved materialsdistribution of the feed system to achieve a new optimized model, so as toimprove the feed system’s static&dynamic performance.Static analysis was carried out for the optimized high-speed verticalmachining center feed system model. Comparing the results with former model,we found that the static stiffness was increased10.3%in X,22.6%in Y,0.24%in Z. Reliability analysis based on the probability of fuzzy reliability theory wascarried out for the optimized model. Comparing the results with the formermodel, we obtained that the first eight orders’ inherent frequency all increased,except6thand8thdecreasing slightly, especially the5thorder natural frequencyimproved greatly, by9.23%. The optimized feed system’s anti-resonance fuzzyreliability was99.986%.