Research On Surface Quasi - Flexible Polishing Technology Based On Slow - Knife Servo

NRS(Non-Rotationally Symmetric) surface is a complex aspheric surface, it has not rotating shaft and is a kind of freeform surface. It can correct the aberration, improve image quality, simplify the system and shorten the working distance. Ultra-precision machining of NRS surface is becoming a research hot spot.The flexible polishing technology based on slow tool servo method is mainly discussed in this paper, polishing experiments of the freeform surface is studied deeply with CNC turn-milling machine tool. The main research contents are as follows:The contact and material removal characteristics of the flexible polishing are studied to obtain the formation process of polishing contact area, the polishing force is analyzed also. According to Preston equation, the linear influence of the polishing parameters on material removal is evolved.In order to avoid the extreme cutting condition that cutting speed on the center of the workpiece is zero, ensure that each point on the surface of the parts can get enough cutting speed and good processing quality, the multipoint clamping device of workpieces is developed based on the constructing principle of slow tool servo technology, layout form and linkage of machine tool.In order to ensure the precision index of center height of polishing head in the experimental system, the space structure of experimental device of the flexible polishing is researched on the basis of processing principle of STS and needs of flexible polishing. In order to obtain the regression curve of driving frequency and speed of the motorized spindle, ensure the experimental precision index of the speed, the calibrating experimental system of the driving frequency and speed is designed and the software used for testing the speed is developed. To study the relationship between the stress of flexible polishing head and polishing quality, cutting dynamometer(Kistler 9257B) is adopted to realize the online measurement.The processing method and the cutting pattern in CAM environment of parts are analyzed. The polishing path of experimental surface is researched and the post-processors of different working conditions are developed. The NC codes which based on tri-axial linkage of ZXC can be generated automatically by the post-processors.The effect law of the change of polishing factors on the surface quality and polishing force is explored through the single factor experimental method of flexible polishing on freeform surface. In order to obtain optimal polishing parameters and surface machining quality, the significant degree of various polishing factors on the 3D surface roughness of freeform surface parts is investigated using the orthogonal experimental method.