Study On Dynamic Performance Of Drill Collar Spiral Groove CNC Milling Machine

Being widely used in manufacturing industry today and with the higher requirementconsumers asked for its performance, researching machine tools with high efficiency, highprecision is the trend of development in Chinese machine tool industry. Machiningperformance is closely related to dynamic performance. The developments of finiteelement technology, computer technology and dynamic test technology have promoted theresearch of machine tool’s dynamic performance. It is the inexorable trend to analyzemachine tool’s dynamic performance during the design process.First, recent study of machine tool dynamic performance at home and abroad wassummarized in this paper. Finite element analysis (FEA) theory applied to machine tooldynamic performance, the drill collar spiral groove CNC milling machine structure,principle and process were introduced. Then the dynamic performance of machine baseand spindle were studied using finite element method. In the prediction of the base’sdynamic performance, machine base model was built according to design sketches and thefirst6natural frequencies and mode shapes were extracted. By comparison with themilling cutter’s excitation frequency, the excitation frequency is between the base’s firstand second-order natural frequency. This result indicates that the base structure isreasonable and will not cause resonance. In the study of dynamic performance of spindle,the spindle’s first-order natural frequency was calculated by equivalent diameter method.The spindle’s different boundary conditions, unrestrained and fixed restrained werepredicted by finite element method. And the bearings’ stiffness was studied to analyzeelastic restrained spindle’s dynamic performance. Under different conditions, the spindle’sfirst-order natural frequency is greater than milling cutter’s excitation frequency, indicatingthe reasonable structure of machine spindle. Finally, after the spindle manufactured,hammering method tests were carried on to test the natural frequencies of free andassembled spindle. It turns out that free dynamic test result is close to FEA result, but assembled test result differ considerably from FEA result. The error was analyzed and FEAmodel was improved. Reanalysis result is close to the test result. The test again proves thegood performance of the spindle. It also indicates that the FEA predict results aresubstantially correct.Research shows that by using finite element method to predict the structure dynamicperformance is feasible. Relatively accurate result is available on the condition of dealingboundary conditions practically. For some complex boundary conditions, theoreticalcalculation methods need further research. Conducting dynamic test to provide relevantdata for theory analysis is available.