Study On Key Problems Of Mechanics In Large Vertical Glass Edge Grinding Machine

At present, the building energy consumption of unit area in China is two or threetimes as much as one of developed country, energy consumption of building is about27.45percent of the national one. Glass window and door is called heat cavitybecause the heat loss via it is high to50percent of total building energy consumption.Insulating glass is a building energy saving material with high performance to priceratio because of its heat and noise insulation effect, it has wide market foreground.Grinding glass edge is an important process of insulating glass manufacture, itcan eliminate disfigurements like micro-crack and stress centralization of glass edgeproduced by cutting process, avoid damage to operator or machine of next processesand improve finished product rate of glass tempering procedure. Vertical glass edgegrinding machine has many excellent performances such as small floor area, easyadjustment and automatic identifying the length and width of glass, which is suitablefor batch machining of multi-variety and multi-specification glass.The market of vertical glass edge grinding machine in China has been occupiedby foreign corporations such as Rising Star Glass Machinery Corporation of Koreaand Bystronic Group of Switzerland. The vertical glass edge grinding machinedeveloped by China has some problems such as locked rotation of grinding wheel,significant vibration and lower starting acceleration of grinding wheel carriage etc.,due to the lack of research on key mechanics problems like grinding force, dynamicanalysis of grinding wheel carriage and its rapid response characteristic of drivingsystem. Hence, the study and breakthrough on above key problems of mechanics hasimportant theoretical and practical values for the domestic manufacture, importsubstitution and appropriate use of large vertical glass edge grinding machine.Grinding force is an important parameter during grinding process. According tothe structural characteristics of vertical glass edge grinding machine like grindingwheel cantilever installation, narrow space and wretched environment etc., the paperinnovatively designed a strain type grinding dynamometer which adopted ladder shaftsleeve as elastic component, finished orthogonal test of grinding force and establishedgrinding force forecast model. The average error is less than5percent between valuescalculated by grinding force forecast model and actual measuring values. The extremedifference and variance analysis of orthogonal test data indicates that grindingparameters have important influence on grinding force, the primary factor is chamfersize c, the secondary one is feed rate vfand the tertiary one is grinding wheel velocityvc, tangential and radial grinding forces increase with the accretion of c and vf,tangential grinding force decreases with the increase of vcwhich has little effect onradial grinding force. According to the analysis results about stationarity, periodicity and spectrum of dynamic grinding force signals, the grinding force signals of edgingglass are periodic vibration signals with stationarity, its characteristic frequency isequal to the rotating frequency of grinding wheel. The research results establish thetheoretical base for the design of grinding process control strategy and theoptimization of grinding parameters about vertical glass edge grinding machine, theproblem about locked rotation of grinding wheel is solved.The grinding quality of glass edge was influenced directly by the vibration ofgrinding wheel and grinding wheel carriage. Two dynamic models called1DOF and2DOF system were founded according to the structure of grinding wheel carriage, thevibration characteristics and rules of grinding wheel and grinding wheel carriageeffected by periodic force were analyzed. The analyzing result of1DOF model showsthat the vibration response of grinding wheel carriage includes transient response andsteady response. The system natural frequency will be improved, transient responseprocess will be shortened and steady vibration amplitude will be reduced byenhancing the axial rigidity of system, steady vibration amplitude decreases with theincrease of damping ratio ξ. The analyzing result of2DOF model indicates thatvibrations of grinding wheel carriage and grinding wheel are related with mass ratio μ,natural frequency ratio α and damping ratio ξ of system, the expressions of reasonableμ, α and ξ were educed in order to get small and equal dynamic amplification factor ofgrinding wheel and grinding wheel carriage at resonance, which successfully resolvesthe problem on dynamic design of vertical glass edge grinding machine.Natural frequency and modal shape are inherent attribute of system, they aredetermined by system structure instead of outside force. The finite element model(FEM) of grinding wheel carriage was established based on ANSYS parametricdesign language (APDL) which considering dynamic characteristics of moving joints,frontal four modal shapes and natural frequencies were analyzed, the average errorcalculated by FEM is less than23percent compared with the result of experimentalmodal analysis. The influences on natural frequency of system by the diameter of ballscrew, the fixing board thickness of slide block, the contact rigidity of ball screw andbearings and the working position of grinding wheel carriage were investigated. Theresearch results offer a scientific basis for the improvement of dynamic characteristicand reasonable use of vertical glass edge grinding machine. After improvement,natural frequencies of grinding wheel carriage are increased more than10percent, soits dynamic characteristic and anti-vibration ability are improved.In order to improve the rapid response ability of grinding wheel carriage, theoptimization design model on the transmission ratio of lifting drive system based onmaximum starting acceleration of grinding wheel carriage was established, whichconsiders restriction conditions such as inertia match, speed match and torque match.The optimal transmission ratio was calculated by in-point method of SUMT (Sequential Unconstrained Minimization Technique) and was applied to the design ofsecond generation glass edge grinding machine. The maximum starting accelerationof grinding wheel carriage was improved22.95percent and its feed rate wasimproved77.78percent based on actual test data after optimization.The second generation glass edge grinding machine based on above researchresult was used by two corporations in China, its actual application for more than oneyear shows the machine is in good condition.