Analysis On Structural Dynamic Characteristics And Optimal Design For The Bed Of Turning-milling Machining Center

Due to the improvement of the High Efficiency Machining(HEM)technology,the cutting speed of the machine centers is increasing dramatically and constantly,meanwhile some new requirements of the composite function of them are put forward as well.The evaluating indicators of the quality and performance of a machine tool is no longer limited to the static characteristics but be mainly depended on the dynamic characteristics of this machine tool which can determine the machining accuracy,the quality of workpiece surfaces,the production efficiency and the normal lives of the cutting tools.As a consequence of this,the study on the dynamic characteristic of the machining systems has been a critical and general technical issue of the Research and Development(R&D),design and manufacture of high-grade Numerical Control Machine Tools.The modal analysis of the CK6140 turning-milling machining center bed has been done in this article.Based on the modal simulation analysis of the bed with a finite element analysis software called Workbench,a numerical solution which consists of the bed's first thirty natural frequencies was worked out,then first thirteen numerical modal parameters were obtained;Based om the SIMO(Single Input Multiple Output)hammering method the experimental datum was collected,then the frequency response functions based on experimen-tal datum were curve-fitted and parametric identified by the Matlab program of Least Squares Complex Exponent(LSCE),then first thirteen experimental modal parameters were obtained;Compared with the experimental outputs and the simulation numerical calculation outputs,the simulation numerical calculation method has been proven to be accurate and reliable.The dynamic characteristic analysis of the CK6140 turning-milling machining center bed has been done in this article.The milling forces were calculated,the deformations and harmonic responses of the bed were analyzed on the Workbench simulation platform.The analysis result showed that the first three modals' natural frequencies and the formant frequencies of harmonic responses analysis were almost overlaped,it proved that the bed was sensitive to lower modals especially the first modal.It will lead to drastic resonance if the working frequencies approach to these lower frequencies.The optimization design of the CK6140 turning-milling machining center bed has been done in this article.A Equivalent dynamic model of mechanical joints between the damping and the casting cavity of the bed was built through Takashi Yoshimura integration method.Putting the properties and quantity of the damping as design variables,putting the reduction of the maximum amplitudes of the bed's dynamic responses under actual operating condition and the improvement of lower natural frequencies as optimization objectives,the reasonable design variables were determined,the dynamic optimization project of additional damping to the bed was also came up with.Finally,the dynamic characteristics of the bed was improved significantly with analysis of this optimization project.