Dynamic Simulation And Optimization Design Of Vibrating Ball Mill

The vibrating ball mill is a solid sample grinding equipment commonly used in the laboratory of biology,medicine,chemical industry and other fields.Precision and lightweight are the development direction of this instrument.In this paper,a high energy vibrating ball mill is taken as the research object,aiming at the problem of insufficient strength of key parts and strong vibration during operation of the grinding instrument.The dynamic analysis of the core mechanism of the grinding instrument and the analysis of the mode characteristics of the whole machine were completed.On the basis of dynamic simulation analysis theory of grinding instrument,a new structure design scheme of grinding instrument was proposed.The main research contents and conclusions are as follows:Firstly,In order to study the dynamic characteristics of the mechanical system of the vibrating ball mil,the Kineto-static analysis was used to solve the displacement,velocity,acceleration and force of each member of the crank-connecting rod mechanism of the vibrating ball mil in a movement cycle,which was used as the theoretical basis for the subsequent structural strength analysis of the vibrating ball mil.The single freedom,two freedom and three freedom vibration mechanics models of the whole grinding instrument were established by using the method of concentrated parameters,and the displacement response curves were solved.Secondly,In order to explore the reasons for the strong vibration of the whole machine and the insufficient strength of the key parts,the modal analysis of the whole machine and the structural strength analysis of the connecting rod and the motor support of the vibrating ball mill were carried out by the finite element analysis method.The modal analysis results show that when the operating vibration frequency is 25～35Hz,the existing grinding instrument is very likely to have resonance phenomenon.The existence of low-order resonant frequency band is the main reason for the strong vibration of the grinding instrument when it starts and stops.The results of statics and fatigue strength simulation show that insufficient fatigue strength is the reason of failure of connecting rod.The fatigue life of the motor support meets the requirements and can be replaced regularly.Therefore,it is necessary to optimize the modal characteristics and fatigue strength performance of the whole grinding instrument.Finally,the response surface optimization method was used to optimize the structure of the vibrating ball mil.The sample data points were obtained based on the central composite design experiment.The standard response surface was used to fit the relationship between the design variable and the output variable.Screening,MOGA and NLPQL algorithms were used to solve the optimal design variables,and a new structural design scheme was obtained.After optimization,the first to sixth mode natural frequency values are all lower than 30 Hz,and the seventh to 15 th mode natural frequency values are all higher than 100 Hz.After optimization,the maximum equivalent stress of the ultimate tensile stress is reduced by 58.7%,and the fatigue life of the connecting rod structure is increased by 1.4 times.The ultra-high speed profile measuring instrument was used to measure the vibration amplitude of the vibrating ball mil before and after optimization.The experimental results show that the amplitude of the vibrating ball mil in each frequency segment decreases after optimization,and the maximum amplitude change rate is-57.4%.In addition,the strong vibration of the whole machine disappears when the machine is started and stopped after optimization,which indicates that the modal characteristics of the whole machine are optimized well.