零件加工误差与机床几何误差映射关系建模

At present, the modeling method of geometric error and the accuracy of parts does not consider tool's position deviation and gesture deviation in machining. In order to establish a mapping relationship between geometric error and part error that conforms with machining process and realize the prediction of the part machining error a three-axis machine tool is used as the research object. Firstly, the model of tool position error and tool axis vector error of machine tool are established by using the theory of multi-body system dynamics. Then, the geometric error data of machine tool are identified by using laser tracker and 21 errors of machine tool are obtained, and 18 errors related to position are fitted to build an error space of machine tool. Finally, the typical part features such as part width, flatness, and hole axis position error are selected combined with the moving path of the cutter in machining, and the model between the machine tool geometric error and the part features is established. The accuracy of the model is verified by experiments. The experimental results show that part width error is related to the geometric error of the tool tip, and the differences between measured value and calculated value of part width at 11 points are within 5 μm; the zigzag milling flatness error analysis needs to discretize the tool path firstly, then discretize the tool circle and calculate the point error of the tool circle, finally select the points that belong to the machining face and calculate the flatness error by using the least square method with those points, and the difference between the measured value and calculated value of flatness error is within 2 μm; the position error of hole axis analysis needs to consider the tool tip error and the tool axis error at different positions during the drilling process, then establish the hole equation with those two, and finally obtain the error of the center of circle in corresponding plane by substituting the height value of the measurement plane into the equation. The difference between measured value and calculated value of the position error of hole axis is within 5 μm.