Error Measurement And Identification Of Rotary Axis Of NC Machine Tools

With the development of manufacturing technology, the demand formechanical parts with complex geometric shape and high accuracy isincreasing, and more and more5-axis machine tools are used on themanufacture of mold and aerospace components. Generally,5-axis machinetools contain3linear axes and2rotary axes and are able to provide rotaryfeed, compared with3-axis machine tools. The topology of5-axis machinetool is complicated, and many motion errors are related with each other,which brings a lot of difficulty for error measurement and identification. Thethesis is focused on the error measurement and identification for rotary axisof5-axis machine tool.First of all,5-axis machine tools with common topology are introducedand kinematic modeling with homogenous transformation matrix method isinvestigated. Topology of machine tool is devided into2chains:“machinebase to workpiece” and “machine base to cutting tool”. A5-axis machinetool with tilting rotary table is used as an example to show the generalkinematic modeling process which reveals the connection of error motionsof axis and volumetric error of “workpiece to cutting tools”.Second, based on the circular test with double ball bar, errormeasurement and identification methods for single rotary axis and doublerotary table are investigated. Homogenous transformation matrix is used forkinematic modeling. According to single rotary axis,2measurementpatterns are designed and based on the2patterns,4kinematic errors ofrotary axis is identified. For tilting rotary table,6kinds of measurementpatterns are investigated, and for each measurement pattern,3axis including 1rotary axis move synchronously. Identification method for8kinematicerrors for tilting rotary table is proposed, that is “radial—tangential—axial”measurement. MATLAB is used simulate the identification methods.Then, cutting test on a workpiece to identify8kinematic errors isresearched.11cutting patterns with straight end mill is investigated, throughthese cutting patterns, machine tool feed in1direction. There is arelationship between the finished workpiece and8kinematic errors, andidentification algorithm is proposed.Finally, cutting test of a cone frustum for5-axis machine tools based onNAS979is researched and evaluated. Postions of each axis when doing5-axis synchronous motion for cutting a cone frustum is calculated. Motionerrors of a tilting rotary table is defined and modeled with simplication. Theinfluence of different kinds of motion errors is investigated for thecircularity of cone frustum. Methods of using DBB to simulate the cuttingprocess is investigated and analysed, and the sensitivity of displacementsensor to the parameters of cone frustum is analysed.