Sub-regional Processing With Variable Parameters In Slow Tool Servo Turning For Complex Curved Surface

There are continuously new requirements from the aspects of cutting-edge technology including precise physics experiment,advanced equipment engineering,intelligent manufacturing,etc.for the complex curved surface parts with geometric features as high gradient,surface fluctuation in circumferential direction and local rapidly varied curvature,etc.Compared with other high performance manufacturing technology,precision turning is prone to obtain the surface in high surface integrity and great surface finish surface finish because of its continuity for cutting motion as well as high rigidity machine tools which has made specific difference in high precision and high efficiency manufacturing for the key components.With the promotion of Slow Tool Servo(STS)system and its related technologies,an innovative formation movement of turning process has been gradually applied to the precision manufacturing for the complex curved surface.However,the majority of the researches in STS turning is proposed by the global processing with uniform parameters in the whole machining region,which leads to tool wear,surge of surface residual stress and unevenness of machining error due to the extreme conservative parameters taken in order to guarantee the machining quality.On the contrary,the sub-regional processing method would effectively deal with this issue.However,the existing sub-regional processing methods are focused on the general NC milling center without consideration of the formation movement feature of STS turning which might break the continuity of its cutting motion.What is worse,these methods couldn't associate the geometric factors with the physical factors during machining,whose surface segmentation results would not make a guidance for sub-regional processing planning.Based on the above,a sub-regional processing method with variable parameters in STS turning would be proposed in this paper.The specific research contents are as followings.(1)Sub-regional processing along the axial direction with variable parameters based on potential field in STS turning for complex curved surface.Firstly,the mechanism of specific toolpath topology generation in STS turning is analyzed and the equipotential line with continuity is taken as a guidance for surface division.Thus,a potential field is built based on the equipotential lines which can express the local geometric feature of complex surface.Then,based on the field theory,the scallop-height averaging coefficient is defined and calculated as the basic for establishing surface division criterion.After the surface division,the sub-regional toolpath with variable feed rate is generated according to the equipotential lines which can ensure the feeding motion stability of X-axis in each sub-region.For guaranteeing the continuous cutting motion,the toolpath stitching between adjacent sub-regions is carried out.Moreover,the surface is subdivided with the comprehensive consideration of feeding motion stability of Z-axis and variable spindle speed is designed in different sub-regions.Finally,the sub-regional processing planning in STS turning is finished.(2)Sub-regional processing in circumferential direction with multi-feeds in STS turning.Focusing on the sudden changes of the geometric parameters as well as the sub-regional processing parameters along the circumferential direction,the surface would be segmented along the circumferential direction based on the Fourier Series Expansion.Then,the multi-feeds processing would be design and the proper machining path would be generated and modified in order to avoid the imprecise toolpath stitching.(3)Sub-regional processing in circumferential direction with variable spindle speed in STS turning for noncircular sectional surface based on Fourier Series.Firstly,the surface sectional geometric shape function would be constructed and the complexity evaluation coefficient for noncircular sectional geometry would be defined.Secondly,the sectional profile curve would be pre-segmented where the tool feeding motion trajectory function when machining along each segment would be calculated and expanded into Fourier series and therefore the surface segmentation criterion would be determined.Then,the parameters for sub-regional variable spindle speed function would be determined based on the complexity evaluation coefficient and the magnitude spectral line to realize the sinusoidal variable spindle speed planning.Finally,the toolpath and vacant path would be generated and modified.The sub-regional processing in STS turning for complex curved surface in this paper can can significantly enhance the machining accuracy and surface finish quality with feeding motion stability,which has significant scientific research value and engineering practical value.