| The equivalent cutting force comprehensive error is defined as the superposition results of the geometric errors and the force errors under the condition of constant load. In order to solve existing problems in comprehensive error compensation of geometric error and cutting force error, the actual stress state of the machine tool is simulated by loading constant load to the machine tool, then the equivalent of cutting force comprehensive error consists of geometric error and the force error is measured and compensated on the basis of multi-body system theory. The main research contents of this thesis are shown as follows:The equivalent cutting force comprehensive error compensation model of 3-Axis machine tool is established. Though analyzing the related principle of multi body kinematics, the topologies of multi-body system, lower body array and homogeneous coordinate transformation are actually applied to the error modeling of 3-axis, the coordinate transformation matrices consisted of geometric errors and cutting force error is derived under the action of loading force. By transferring the coordinate of point to be processed on the work-piece and the coordinate of tool-tip point to the coordinate system of machine tool, the mathematical modeling of the equivalent cutting force comprehensive error compensation is achieved. it provides a theoretical basis for improving the manufacture precision of CNC machine by software compensation.The constant loading device is designed, and the corresponding relationship between the force and the equivalent cutting force comprehensive error is directly established. The actual cutting force of the 3-axis machine tool is measured by using the SDC-C4 F dynamometer, the measuring result is regard as a reference standard of choosing constant load,the constant load loading device has also been designed, by which the constant load will be loaded to the work-table of the machine, then the actual cutting force of machine tool will be imitated by loading force. On this condition, using laser interferometer can achieve direct measuring to the equivalent cutting force comprehensive error. It’s unnecessary to respectively measure the geometric errors and the cutting force error anymore, when determine the equivalent cutting force comprehensive error, it voids the operation of summing for the geometric errors and the force error, and then the geometric error and the cutting force error achieve the automatic coupling.The error compensation software of equivalent of cutting force is developed. On the base of synthetically applying MATLAB and Visual studio 2010 software development platform, the proposed error compensation model and the equation for calculating comprehensive error parameters are encapsulated by MATLAB, the command compiler of development tool will make them generate the Dynamic Link Library that the visual studio 2010 can identify it, so the error compensation software can directly calls both of them. Combined with the interpolate algorithm to CNC program, the theoretical studies of error compensation is written running program of error compensation software by C# language, the CNC program will be compensated by the means of software, this method greatly raised error compensation efficiency.Error verification tests have been done through actual machined work-piece. The ideal CNC program, the CNC program with geometrical error compensative and the CNC program compensated by the equivalent cutting force comprehensive error are used to machine the work-piece, respectively. then the contour precision of work-piece machined by the three NC instruction mentioned above will be measured by the coordinate measuring machine(CVA800A-6C), the result of measure demonstrate that the research scheme of equivalent cutting force comprehensive error compensation can significantly improve the processing precision of machine tool, the developed error compensation software can rapidly implement error compensation for machine tool... |
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