Research On Turning Freeform Surface Of Brittle Material By Changing Feedrate

Optical free-form surfaces of brittle materials are highly favored by academicresearchers especially widely used in aerospace field with the process ofsingle-crystal germanium, silicon, quartz glass and optical glass made of opticalsurfaces; currently the main process method of brittle materials is still grinding,because grinding exists inefficiency, it is difficult to complete the process of complexsurfaces and other shortcomings greatly limits the development of optical surfaces.Therefore, this paper will focus on the research of single point diamond turning ofbrittle materials to achieve ductile regime material removal. However, due to lowductility, high brittleness and other characteristics of brittle materials, this paperproposes a tool path planning strategy which controls the cutting thickness in ductileregime, and analyzes the critical effect of diamond cutting tool rake angle on brittlematerial removal. With the constant cutting thickness tool path planning strategy putforward, this paper completes the design and fabrication of a noveltwo-degree-of-freedom differential FTS apparatus.A tool path generation strategy of brittle material removal is completed. Accordingto brittle material ductile regime material removal characteristics, the role of cuttingtool rake angle in the process is demonstrated and analyzed, and takes single crystalsilicon as an example to verify diverse cutting tool rake angles from the processresults to obtain the optimal range of the cutting tool rake angle; In the process ofbrittle material, it is in ductile regime material removal in the beginning, with thecutting thickness gradually changed, it comes into brittle fracture away from ductileregime. There is a critical cutting thickness during the process. Thus the tool pathtake critical turning thickness as constraint condition by establishing the functionrelationship between cutting tool location point interval and turning thickness toachieve constant cutting thickness through controlling constant cutting tool locationpoint interval; In the tool path calculation procedure, cutting tool rake anglecompensation is completed first of all due to the existence of non-zero rake angle; next cutting tool contact points are calculated; the tool path is completed via cuttingtool nose radius compensation to calculate the cutting tool location points’ position atlast.The design and fabrication of a two-degree-of-freedom FTS apparatus iscompleted. To ensure its two axial motion without disturbing each other and toachieve accurate motion, the design process is fully considered the issue of motionaxis decoupling. The flexure hinge motion transmission unit adopts integratedstructure, on the one hand to avoid assembly errors between hinges, another is toincrease the flexible hinge motion accuracy to avoid inter-hinge displacementconsumption result in reduction of apparatus’s performance. Leaf-spring flexurehinge is adopted in motion transmission unit with the completion of connecting andfixing the motor with the Z-shaped flexure hinge in the same plane of the motormotion, the calculation process uses a relatively accurate compliance matrix approachto complete each flexure hinge flexibility analysis and calculation; Z-shaped flexurehinge as the main achievement motion part, its material is selected as65Mn whichhas strong recovery property, uses compliance matrix approach to analyze itsflexibility model and motion performance.System noise test is conducted on condition that the motor is cut power and notworking, analyzes noise impact on system environment under diverse conditions;Open-loop tests two axis motion strokes of the apparatus; Take z-axis motion as anexample to measure the x-axis crosstalk while z-axis driven motor is working, and itscrosstalk rate is below one percentage; System tracking performance is in the range oftheoretical parameters.