Study On Key Problems Of High Speed Machining Center Dynamics

As the development of tools, driving and control technology, high speed machining is applied widely. The high speed machining center is the key equipment of high speed machining, the key issues in developing a high speed machining center are studied in this paper. The research results have great value to manufacture a machining center with high qualities static and dynamic characteristics. The main contents are:(1) To design the mechanical structure of high speed machine center. The transmission system adopts the high speed ball screw to achieve rapid feed velocity. A close loop feedback control strategy is used. Under the constraint of mass and low order natural frequency and the dynamic stiffness is optimized object, the optimal process is studied to achieve the thickness of pillar. Dynamic stiffness in x axis is improved17.6%,22.2%in y axis and68.9%in z axis while the mass increase3.1%.(2) The key technology in high speed machining for free curve, NURBS interpolator algorithm is studied, mainly including the Taylor first order and second order method, trajectory planning and error analysis. Error feedback interpolator algorithm and trajectory planning method are proposed. Through the comparison with Taylor method, it is proved that error feedback has the ability to constrain the interpolation error. Based on the above researches, using VB programing language the NURBS curve interpolation simulation platform is designed.(3) The modeling method using Lagrange approach for linear guide rail is discussed. The motion coordinate system of carriage blocks established, and Lagrange approach is adopted to model the dynamical equations along each axis. The natural frequencies can then be obtained from these equations. The finite element model of linear guide rail in ANSYS using APDL language is established to comparison. In the model, spring is adopted to substitute for rolling ball. Model analysis is carried out to obtain the nature frequencies and mode of vibration. Through the comparison of the result, it is proved the mode of vibration of the linear guide system is the motion of carriage, but not the deformation of carriage. (4) The prediction of tool point frequency function is discussed using the receptance coupling substructure analysis method. The assembly response of two components rigid coupling and flexible coupling is studied. The actual spindle-cutting tool system is analyzed, considering of the lateral displacements and rotations about lines perpendicular to the tool, the assembly receptance coupling is discussed. The tool point frequency function is obtained. A solid steel cylinder with a diameter of10mm, and a length of125mm and a holder with a diameter of50mm are taken as example to verify the method. The finite element and one in this paper are compared. It is proved that the result from two different methods are almost seam, the error of Hnis less than1.5%.(5) The vibration testing for machine tool is studied, the experiment step is analysis. Using B&K770Pulse data acquisition and analysis system,514-001,4507B acceleration transducer,8230-001forces transducer etc., single point stimulation multi points acquisition test is carried on. In each direction, the scopes with l00Hz and400Hz are analyzed, the vibration responses are obtained.