Research On Digital Design And Simulation Analysis Of Ultra-High-Speed Grinding Test-bed

With the development of computer and network technology,new features emerge in mechanical manufacturing industry--computer as foundation,digitized information as description,and digital development of the product as method.Compared to physical prototype,a digital prototype based on digital design technology reveals digital illustration of product on a computer.As means and method for establishment of digital prototype in the application of manufacturing equipment product design and development,digital design technology consists of key elements with digital characteristics:computer-aided design technology,computer-aided analysis technology and computer-aided manufacturing technology.Ultra-high-speed machining has become a peak spot in the competition of advanced manufacturing technology,in which ultra-high-speed grinding is a modern processing technology for producing high quality parts efficiently and economically.The carrier for ultra-high-speed grinding is ultra-high-speed grinding machine.In the process of ultra-high-speed grinding,the workpiece and grinding wheel collide with each other at a high speed,which requires machine tools to bear the impact load when the spindle rotates at high speed while the processing accuracy of the machine should be still guaranteed.In order to meet the above requirements,the dynamic and thermal characteristics of the whole ultra-high-speed grinding machine and the spindle system on it need to be accurately predicted and designed.In the process of structural design,the grinding mechanism in the contact area between the wheel and the workpiece,the supporting characteristics of the spindle bearing system at high speed/ultra-high-speed,and the dynamic response of the whole machine structure under thermal-structural coupling to varying load need to be solved urgently.In 1996,the Institute of Advanced Manufacturing and Automation of Northeastern University developed the first high-power ultra-high-speed grinding test-bed in China,which has a wheel speed up to 250m/s,filling in the gap in the country at that time and promoting the development of high-speed/ultra-high-speed grinding research in our country.But in recent years,with the development of spindle technology,motor technology,high precision rail technology and other hardware equipment and computer software technology,the design and manufacture of machine tools have reached a new height.Furthermore,after more than ten years' operation,the test-bed cannot satisfy current ultra-high-speed grinding research regarding the machining precision and the mechanical properties.Taking the ultra-high-speed grinding test-bed of Northeastern University as target,the theory,simulation and experiment of its digital design and simulation analysis are carried out.The influence of the grinding process on the structure design of the ultra-high-speed grinding test-bed,the dynamic and thermodynamic characteristics of the spindle system and the whole machine structure,and the solution to key problems in the construction of the simulation system,as well as the problems existing in the test-bed for the design and transformation of the super-high-speed grinding machine are discussed.To this end,the main contents of the paper are organized as follows:(1)The simulation of grinding process in ultra-high-speed grinding process is studied by finite element simulation method,specifically the macro simulation of grinding temperature and grinding force are investigated.The feasibility and rationality of grinding simulation using finite element method are expounded theoretically.The dynamic curve of grinding force and grinding temperature are obtained according to different grinding speed and grinding depth.The grinding force and temperature under different parameters are measured using three-direction dynamometer and thermocouple.The theoretical calculation results,the simulation analysis results and the experimental results are compared and analyzed to verify the correctness of simulation analysis.(2)Dynamic characteristic simulation and experimental research on dynamic and static hydraulic bearing spindle system,which is the key parts of the ultra-high-speed grinding machine,are implemented.The fluid dynamics method is used to analyze the pressure field and temperature field of the dynamic and static hydraulic bearing.The bearing characteristics and temperature variations are described with respect to different eccentricities and spindle speeds.The dynamic parameters of bearing support are calculated using dynamic grid method.The finite element method is applied to the finite element modeling and dynamic characteristic analysis of the spindle system.The natural frequency of the spindle system is measured to verify the simulation analysis.The existing problems of current spindle system and the direction of improvement are proposed.(3)The dynamic characteristics of ultra-high-speed grinding machine are analyzed,and the simulation analysis method is studied.According to classification of different structure joint parts on the machine tool,the theoretical equivalent substitution of the dynamic parameters of the joint parts is analyzed and calculated.The equivalent substitution of the dynamic stiffness and damping of the joint parts is studied in the finite element analysis,and the dynamic equivalent substitution method of the key joint parts of the machine tool is proposed.In view of the interactive analysis of machining simulation and structure simulation,the dynamic characteristics of the whole machine are analyzed.The natural frequency measurement and the response analysis of the machining process are carried out to verify the simulation analysis,the key factors affecting the whole machine dynamics and direction of improvement are proposed.(4)In view of the obvious characteristics of thermodynamic problems in the operation of high-speed/ultra-high-speed equipment,the thermal-structure-couplingproblem of mechanical structure is studied.The thermal-structure coupling analysis of spindle system is carried out based on the simulation analysis of grinding process and bearing temperature field analysis of spindle system.The heat source of spindle system under different grinding conditions is analyzed,and the three-dimension temperature field is solved using finite element method.On the basis of the solution to the temperature field and the stress analysis of the spindle system,the thermal-structure coupling analysis is applied to the spindle system.The displacement variations under multi-field conditions are analyzed.(5)Virtual machining simulation system for ultra-high-speed grinding machine based on network is studied.The digital model of machine tool is published on the network platform,and the machine tool movement simulation and interference check are carried out using network language programming.The code compilation is carried out,and the NC code compilation technology and the entity Boolean operation are used to control the machining process of the machine tool.The grinding process geometric simulation is implemented.The physical simulation of grinding process is studied using Matlab language network interface for compiling related programs and calling geometric simulation parameters.