Research On Turn-Milling Of Low-rigidity Workpieces

Turn-milling is an advanced processing technology which realizes the material removal based on the synthetic motion of workpiece rotation and cutter rotation.Turn-milling can combine workpieces rotating at low speed with high-speed cutting, and it is suitable for machining low-rigidity workpieces such as micro shaft, slender shaft. On the basis of ralative throries of turn-milling and low-rigidity workpieces machining methods, turn-milling composite machines was reformed based on common lathe, and Turn-milling machining of stainless steel low-rigidity workpieces was carried out. The main theses of this research are as follows:To ascertain the surface morphology and the production coditions of various morphology, relative experiments were conducted. The results show that group of pit morphology can be achieved at non-integer rotating ratio, and groove shape can be achieved at integer rotating ratio. When the axial feeding is 0.085 mm/r, remarkable group of pit morphology can be achieved controlling the rotating ratio between 60 and 150. The rotating ratio reaching 300, the group of pit morphology disappear entirely.To analyze the influence of cutting parameters on surface quality, relative experiments were conducted to get optimum surface quality. The results show that better surface quality can be achieved on the conditions of being the low workpiece rotation, the high cutter rotation, the small cutting thickness. The optimum cutting conditions are workpiece roration 60 r/min, cutter rotation 16000 r/min, cutting thickness 0.1 mm.The dynamic characteristics of turn-milling of low-rigidity workpiecs were studied using Matlab. The influence of workpiece rough diameter on inherent frequency was analyzed. The results show that chosing proper workpiece rough diameter can keep away from inherent frequency to realize suppress vibration. Dynamics analysis of turn-milling of slender shaft shows that the vibration displacement of turn-milling is lower than turning, and high-speed turn-milling can diminish vibration displacement furtherly.To validate the advantages of turn-milling of micro shaft, machining experiments of micro shafts of different materials and various sizes were carried out. The results show that cutting parameters have a large effect on axial dimension precicion. The optimum process conditions are as follows:workpiece roration 50 r/min, cutter rotation 18000 r/min, cutting thickness 12.5 um, and the dimensional error is 3.18 μm. To verify the advantages of turn-milling of slender shaft, the turning and turn-milling of slender shaft were carried out. The results show that turn-milling can significantly suppress flexural deformation, and the surface quality has improved greatly. Under the optimum process conditions, φ10mm × 240 mm stainless steel slender shaft with the dimensional accuracy better than 0.015 mm can be obtained.