Thermal Characteristic Analysis And Optimization Of Horizontal Machining Center With Double Spindles

Among many factors that affect the machining accuracy of machining center,the thermal error caused by the thermal characteristics of machining center accounts for 40 %-70 %of the total error of machining center.Therefore,it is an important way to improve the production accuracy by analyzing the mechanism of thermal error and its changing trend.The research object of this paper is the domestic double spindle horizontal machining center,which is mainly used in the production line of car engine assembly core parts,and the accuracy requirements are much more strict.Therefore,it is necessary to analyze and optimize the thermal characteristics of domestic double spindle horizontal machining center,so as to improve the accuracy of machining center.Specifically,this paper mainly studies the domestic double spindle horizontal machining center from four aspects: thermal characteristic modeling,thermal characteristic analysis,thermal characteristic optimization and thermal characteristic model verification.The specific research contents are as follows:(1)According to the generation mechanism of thermal error of general machining center,combined with the structural characteristics of double spindle horizontal machining center,a general thermal characteristic model for calculating the thermal boundary conditions of horizontal machining center with double spindle structural characteristics is established.The model mainly includes: equivalent mechanical load model,heat generation model and heat dissipation model.Among them,the equivalent mechanical load model mainly simplifies the forces and moments received by the machining center;the heat generation model mainly carries out quantitative analysis according to the generation form of the internal heat source of the machining center;the heat dissipation model mainly carries out quantitative analysis on the main heat dissipation mode of the machining center according to the heat transfer theory.(2)Under the given simulation condition,the thermal boundary condition of the horizontal machining center with double spindles is calculated based on the thermal characteristic model.The thermal structure coupling simulation is carried out based on the finite element simulation tool.The steady temperature field and the deformation field under the combined action of the heating load,the heavy load and the heat and the gravity load are obtained.Finally,the law of temperature field change,the law of guide rail deformation and the law of spindle deformation are analyzed,which provide some reference for the design and optimization of the thermal characteristics of the horizontal machining center with double spindles.(3)Based on the influence of thermal deformation of machining center on its accuracy,the characteristics of different heat dissipation optimization methods of machining center are analyzed.Finally,according to the simulation results of the thermal characteristics of the double spindle horizontal machining center,on the premise of not changing the structure of the machining center,the thermal characteristics of the double spindle horizontal machining center are optimized by adding cooling water device to the high temperature area to increase the heat dissipation of the machining center.The optimization results show that the maximum temperature of Y1 motor,Y1 bearings which near motor,Y1 bearings which far away motor and Y1 nut are 69.46%,55.13%,39.79%and4.25 % lower than that before optimization.The maximum thermal deformation of Y1 left and right guide rails decreased by 68.01% and 70.18% respectively compared with that before the optimization of heat dissipation;the maximum thermal deformation of Z1 and Z2 axes decreased by 55.97% and 67.41% respectively compared with that before the optimization of heat dissipation.In addition,the influence of different cooling water flow rate on the thermal characteristics of machining center is studied.The results show that the optimal cooling water flow rate is 15L/min under the given simulation condition.(4)The thermal characteristics of PT50 A horizontal machining center,which is the key part of car power assembly,is simulated and analyzed under the same working condition.Finally,the steady-state temperature data of the experimental points are extracted and compared with the simulated temperature data.The analysis results show that the data errors of 8 measuring points are less than 5% in the temperature comparison of12 measuring points,and the errors of the other 4 measuring points are in the range of 5-10%,which shows that the thermal characteristic model proposed in this paper has certain accuracy and applicability.