Research On Spindle Ram Components Error Compensation Of Floor Milling-boring Machining Center

For the horizontal machine tool with ram, the deformation caused by ram overhangbecomes the weak link of the overall accuracy. The floor milling-boring machining centeris one of such machines. When the floor milling-boring machining center is in themachining work, the cantilever beam structure formed by spindle ram extending under theaction of the gravity and cutting force leads to the spindle axis deviation from the idealposition, seriously affecting the machining accuracy and the processing quality of theproduct.The thesis researched on the deformation of the spindle ram components of TH6918floor milling-boring machining center by the finite element software ANSYS and putforward an error compensation method to reduce the error caused by the ram overhangsagging and improve the precision. The main tasks are as follows:1） The main reasons of the spindle ram components deformation was found out bythe analysis of the mechanical structure of the floor milling-boring machining center. Thedeformations of the ram and boring bar on different strokes were obtained by using theknowledge of the mechanics of materials. Through ANSYS, the deformations of the ramand boring bar on different strokes under the action of the gravity were obtained, also thedeformations of end of the ram under the action of different milling forces were obtained.2） The method of solving the bearing stiffness based on the Hertz theory wasresearched, and the stiffness of the spindle bearings were obtained. The finite elementmodel of the spindle ram components was established by simulating the bearing jointsurface with spring units.3） Through the modal and harmonic analysis, the natural frequencies and modes ofthe ram were obtained, also the ram deformation in different frequency forces wereanalyzed.4） A set of error compensation system was put forward, which is composed of the error compensation of ram deflection and error compensation of head tilt. Based on theresults of ANSYS, the vertical displacement and angle changes were obtained by using thelinear superposition method. The pressure of the rod hydraulic cylinder and the press of therope hydraulic cylinder were calculated by multi-objective linear programming method.And the deformation of the end of ram with a compensation system was compared withthat without a compensation system.5） A PLC-based feedback control system was designed for the ram deformation. ThePLC controls the reducing valves, and the reducing valves controls the pressure of eachhydraulic cylinder to control the compensation mechanism. Then a position sensor is usedfor measuring the error of the end of the ram to perform a feedback control. For the boringbar deflection compensation issue, SIEMENS840D CNC system deflection compensationmodule was used to realize the compensation of Y-axis（compensation axis） to Z-axis（reference axis） according to the pre-set compensation table.