Study On Dynamic Characteristics And Structure Optimization Of The High Speed Grinder

Machined equipment is developing toward high speed,high efficiency,high reliability and high precision.In order to meet the requirement of high processing performance,it is very important for machined equipment whos mechanical structure has excellent dynamic characteristics.The research object of the CNC 8312A high-speed camshaft grinding machine is from the national 863 high technology research and development program"Research on inverse problem and optimization technology in design and manufacture of super high-speed grinding machine".The dynamic characteristics of the main parts of the grinder and the mechanical structure of the whole machine are investigated.The main parts,such as bed,spindle,base of grinding wheel frame and spindle box,have been optimized and designed rationally.The main contents of this paper are summarized as follows:(1)The dynamic characteristics of the original grinder bed and spindle under the free and restrained conditions are analyzed,and the weak structures of the bed and the spindle are found out.This paper explores the influence of the support position and number on the dynamic characteristics of the bed,and a relatively good support design scheme is put forward.Based on substructure method,this paper discusses the influence of different forms,different sizes and different thickness of the substructure element on the dynamic characteristics of the body.The dynamic characteristics analysis of the grinding machine bed based on the material shows that the dynamic characteristics of the machine bed are related to the material of the lathe bed.The comprehensive optimization design of high-speed grinder bed is made in this paper,and the dynamic performance of the bed is improved obviously.Based on the sensitivity analysis method,the four key parameters of the spindle are analyzed according to the optimum dynamic characteristics,the results show that the most sensitive parameter of the spindle dynamic characteristics is the extended section length,and the next is the inner diameter.Based on different materials such as 45,65Mn,60Si2Mn and 40Cr,the grinding spindle of the same structure are simulated and analyzed.It is shown that the change of spindle material has little influence on the low order modal frequencies of the spindle,but the mode displacement of the40Cr spindle is relatively small.The optimum design scheme of grinding machine spindle is put forward.(2)The dynamic characteristics analyses of the spindle box,the upper table and the lower table of the feed worktable are completed,and the finite element analysis software MSC.Patran/Nastran is used to investigate the factors affecting the dynamic characteristics of the bed-worktable assembly parts.Aiming at the goal of light weight for the grinding wheel base,based on the parameter DOE analysis method and the L16(4~3)orthogonal experiment scheme,the direct analysis and regression analysis for three factors are carried out,and the optimal lightweight design plan for the grinding wheel base is put forward.(3)The high speed grinder spindle-wheel rotor system critical speed analysis,stability analysis and unbalance response analysis are finished based on the Transfer Matrix Method,and the low order critical speed and resonance peak of the rotor system are obtained.The analysis shows that the rotor system has no critical load problem and the unbalance response of the rotor is perfect.(4)Using the rail joint simulation technology based on imaginary material and the Takashi Yoshimura integration method,the equivalent stiffness and damping coefficients of the rail joint and the bolted joint are obtained,and the dynamic characteristic for the whole machine has been analyzed.An optimum design method of high-speed grinding machine based on the modal frequency offset method is put forward and the effectiveness of the method is verified.According to the number and diameter of the connection bolt,the bolt fixing joint is optimized,and the resarch shows that the stiffness and damping of the bolt joint can be greatly improved by appropriately increasing the diameter and the number of the connecting bolts,which is beneficial to improve the dynamic performance of the high-speed grinding machine.A method for optimizing the structure of high-speed grinding machine based on minimum tangent point displacement is proposed.(5)Using single input multi output method(SIMO method),in which single point excites vibration and more points collect signal,dynamic characteristics analysis and test on the spindle and the bed-table assembly are completed with LMS SC-305-UTP dynamic signal acquisition and analysis system.Experiments show that the finite element model established in this paper reflects the dynamic characteristics of high-speed grinder,and the theoretical model has good reliability.