Research On The Methods And Key Technologies For Sculpture Surface Machining Error Compensation

With the development of aerospace,national defense,carrier and energy fields,some key workpieces with complex surface are needed to improve machining efficiency and quality.Due to the geometric complexity of the complex surface parts,this kind of parts are usually processed by five-axis machine tool.Based on the key technology for sculpture surface machining error compensation,this paper not only explores the related theories and strategies involved in the prediction of cutting force in five-axis machine,the compensation of tool deflection error,on-machine verification(OMV)and the error feedback compensation,but also probes into the verification of the experiments.In this paper,the machining process of “precompensation-inspection-compensation” for complex surface is completed,which has great significance to improve the machining accuracy and reduce the scrap rate.Based on the kinematics theory of five-axis machine,the transformation is used to establish the relation between tool and workpiece in process.A novel undeformed chip thickness model in five-axis ball-end milling is presented.According to the study of Altintas,the model of cutting forces in five-axis milling based on tooth trajectory is established.The effects of the plough force are taken into account in this model.The method of identifying ploughing force and shearing force coefficients is given.Based on the cantilever beam theory,a strategy to compensate the surface error due to tool deflection in five-axis milling process is proposed.The mirror method is extended to compensate the tool deflection induced surface error by modifying the tool position and orientation in five-axis milling operation.Considering the effect of compensation reference,the calculation of referenced tool position and orientation is presented.The system of on-machine verification for five-axis machine is constructed.With the design of each function module,the system has completed the task of complex surface inspection points planning,extraction information of the sampling points,path planning,NC code generation as well as path simulation.By processing the inspection data,a error feedback compensation strategy based on OMV technology is proposed.Calculating the normalfanyi distance between measuring points and theoretical surface,the mirror method is developed to obtain the location.Using the theory of NURBS surface fitting,the compensation point cloud is used to get compensation machining profile by surface fitting.Theoretical surface model is reconstructed in the three dimensional software and tool path is re-planned in subsequence compensated machining.The results of this paper provide a feasible and scientific theoretical support to the “machining-measurement-compensation” quality control process for complex surface parts.