Tool Path Planning Method For Slow Tool Servo Grinding Of Complex Curved Surface

With the rapid development of China ’ s national defense,aerospace,optics and other fields,the complex surface parts with the characteristics of circumferential contour concave and convex fluctuation and local curvature abrupt change have been widely used.This kind of parts often use difficult-to-cut material with high hardness and brittleness.In order to ensure the service performance of parts,more stringent requirements are put forward for the processing surface quality of such parts.With the development of slow tool servo technology,slow tool servo grinding has become an important method to achieve high quality and high efficiency machining of such complex surface parts.At present,the tool path planning method for slow tool servo grinding of complex surface still has the following shortcomings.Firstly,in the process of complex surface grinding,the traditional calculation method of grinding wheel grinding point position is not fully applicable,which is easy to cause the error calculation of wheel geometric parameters and the deviation of tool path.Secondly,the concave and convex characteristics of the circumferential contour of the surface easily lead to tool path fluctuation,which affects the surface quality and efficiency of the parts.In view of the above problems,this paper carried out the research on tool path planning of slow tool servo grinding of complex surfaces,and proposed a tool path planning method for high quality machining of complex surfaces with geometric characteristics such as concave and convex fluctuation of circumferential contour and abrupt change of local curvature.The specific research contents are as follows:(1)The determination method of grinding wheel geometric parameters considering the full-area machining of complex surfaces and non-interference.Firstly,the wheel-surface contact model is established,the calculation of the contact point position between the wheel and the surface in the machining process is completed,and the arc angle of the wheel considering the whole area machining of the surface is determined.Then,combined with the analysis of the geometric characteristics of the surface,the parameters of the grinding wheel arc radius and the grinding wheel rod considering local and global non-interference are determined.(2)Tool path planning method for stationary grinding based on iso-scallop method.Firstly,in order to ensure the tool path continuity,the spiral cutter contact tool path of the entire surface is planned based on the residual height constraint.Then,the cutter-contact points in the concave feature region are adjusted to reduce the fluctuation of velocity and acceleration of each linear axis in the machining process.The cutter-location path is generated by combining cutter-contact points,the geometric characteristics of surface and wheel geometry parameters.Finally,according to the wheel-surface contact model,the C-axis rotation angle of the machine tool is calculated,and the NC machining program of slow tool servo grinding is generated by combining the cutter-location points information and the C-axis speed.The calculation results of the example show that under the same processing requirements,compared with the traditional iso-scallop method,the proposed method can reduce the maximum velocity of each axis by more than 35 % and the maximum acceleration by more than 46 %.(3)The slow tool servo grinding experiment of precision physical experiment sample was carried out based on the ultra-precision grinding platform built by the project.The experiments of precision physics experiment sample are carried out by using the designed spherical grinding wheel and the bowl shaped arc grinding wheel,and the grinding results are measured and analyzed.The grinding roughness of the spherical grinding wheel and the bowl shaped arc grinding wheel reaches 63 nm and 56 nm,respectively.The grinding trace is uniform and small fluctuation observed by the super depth of field microscope,which verifies the effectiveness of the proposed method.The tool path planning method proposed in this paper for slow tool servo grinding of complex surfaces can significantly reduce the velocity and acceleration fluctuations of each axis in the machining process,and can achieve high-quality machining of complex surfaces such as concave and convex contours and abrupt changes in local curvature,which has important theoretical significance and engineering practical value.