五轴联动加工中进给速度的控制算法
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摘要
目的研究刀具进给速度平稳性对五轴联动加工中复杂自由曲面表面粗糙度、轮廓精度的影响。方法首先对五轴联动机床运动过程中的空间线性插补原理进行了分析,推导出插补周期内各轴的分解速度数学模型。根据数控系统中不同的速度指令方式以及刀具在空间的实际运动距离,分端铣和侧铣两种情况,分别建立了刀具空间运动的实际速度计算模型,然后根据机床各轴的最高速度及加速度约束条件,对各轴分速度、分加速度进行校核处理,最终求得刀具实际的合成速度。最后,基于后置处理技术,用开发的专用后置处理软件进行刀位源代码后置处理,采用某叶轮试件进行了验证,并对实验结果进行了分析。结果在复杂曲面加工中,稳定的表面进给速度会获得较高的表面质量及轮廓精度,曲面曲率变化越大,速度变化对加工质量的影响越大。在同等条件下切削,刀具采用恒表面速度与采用恒进给速度相比,获得的叶片进出汽边轮廓误差值由0.1 mm减小为0.04 mm。结论在五轴联动加工中,越稳定的表面进给速度,越能获得较高的表面质量和轮廓精度,对于曲率变化较大的复杂曲面,需要严格控制刀具的进给速度,尽量获得稳定的表面速度以减少过切值,从而提高零件表面质量。
The work aims to study influence of tool feed rate smoothness on surface roughness and contour accuracy of complex freeform surfaces in five-axis machining. Firstly, the principle of spatial linear interpolation in operation of five axis machine tool was analyzed, and mathematical model was derived for velocity component of each axis in the interpolation period. According to different modes of velocity instruction and actual movement distance of the tool in the numerical control system, actual velocity calculation model was built for spatial movement of tool in terms of end milling and side milling. Then speed and acceleration component of each axis were checked and processed according to the maximum speed and acceleration constraints of each axis on the machine tool, and actual synthetic speed of the tool was finally obtained. Finally, based on post-processing technology, special post-processing software as-developed was used for source code post processing of cutter location, and an impeller test piece was used for verification, and experimental results were analyzed. In the process of complex surface machining, high surface quality and contour precision were obtained at stable surface feed rate. Changes in feed rate had great effects on machining quality if surface curvature changed greatly. Under the same cutting conditions, contour error of blade leading and trailing edge was reduced from 0.1 mm(at constant feed rate) to 0.04 mm(at constant surface speed). In five-axis machining, the more stable the surface feed rate is, the higher the surface quality and the contour precision are. For the complex surface exhibiting great curvature change, it is necessary to strictly control feed rate of tool and obtain stable surface speed as far as possible, so as to reduce overcut value and improve surface quality of parts.
The work aims to study influence of tool feed rate smoothness on surface roughness and contour accuracy of complex freeform surfaces in five-axis machining. Firstly, the principle of spatial linear interpolation in operation of five axis machine tool was analyzed, and mathematical model was derived for velocity component of each axis in the interpolation period. According to different modes of velocity instruction and actual movement distance of the tool in the numerical control system, actual velocity calculation model was built for spatial movement of tool in terms of end milling and side milling. Then speed and acceleration component of each axis were checked and processed according to the maximum speed and acceleration constraints of each axis on the machine tool, and actual synthetic speed of the tool was finally obtained. Finally, based on post-processing technology, special post-processing software as-developed was used for source code post processing of cutter location, and an impeller test piece was used for verification, and experimental results were analyzed. In the process of complex surface machining, high surface quality and contour precision were obtained at stable surface feed rate. Changes in feed rate had great effects on machining quality if surface curvature changed greatly. Under the same cutting conditions, contour error of blade leading and trailing edge was reduced from 0.1 mm(at constant feed rate) to 0.04 mm(at constant surface speed). In five-axis machining, the more stable the surface feed rate is, the higher the surface quality and the contour precision are. For the complex surface exhibiting great curvature change, it is necessary to strictly control feed rate of tool and obtain stable surface speed as far as possible, so as to reduce overcut value and improve surface quality of parts.
引文
[1]么居标,曹著明,孙红梅,等.复杂曲面五轴数控加工关键技术研究[J].机械设计与制造,2017(7):128-130.YAO Ju-biao,CAO Zhu-ming,SUN Hong-mei,et al.The Research of Key Technology Based on Five Axis NC Machining of Complex Surface[J].Mechanical Design and Manufacturing,2017(7):128-130.
[2]吴大中,王宇晗,冯景春,等.五坐标数控加工的非线性运动误差分析与控制[J].上海交通大学学报,2007,41(10):1608-1612.WU Da-zhong,WANG Yu-han,FENG Jing-chun,et al.Analysis and Control of the Nonlinear Errors in Five-axis NC Machining[J].Journal of Shanghai Jiao Tong University,2007,41(10):1608-1612.
[3]杨旭静,周元生,陈泽忠,等.五轴数控加工中旋转轴运动引起的非线性误差分析与控制[J].机械工程学报,2012,48(3):140-146.YANG Xu-jing,ZHOU Yuan-sheng,CHEN Ze-zhong,et al.Analysis and Control of Tool Path Interpolation Error in Rotary Axes Motions of Five-axis CNC Milling[J].Journal of Mechanical Engineering,2012,48(3):140-146.
[4]GASSARA B,BAILI M,DESSEIN G,et al.Feed Rate Modeling in Circular-Circular Interpolation Discontinuity for High-speed Milling[J].International Journal of Advanced Manufacturing Technology,2010,65:1619-1634.
[5]RIDWAN F,XU Xun,FREDERICK C L.Adaptive Execution of an NC Program with Feed Rate Optimization[J].International Journal of Advanced Manufacturing Technology,2010,63:1117-1130.
[6]GRAY P,BEDI S,ISMAIL F,et al.Comparison of 5-axis and 3-axis Finish Machining of Hydroforming Die Inserts[J].International Journal of Advanced Manufacturing Technology,2001,17(8):562-569.
[7]BEUDAERT X,PECHARD P,TOURNIER C.5-axis Tool Path Smoothing Based on Drive Constraints[J].International Journal of Machine Tools&Manufacture,2011,51(12):958-965.
[8]NAM S H,YANG M Y.A Study on a Generalized Parametric Interpolator with Real-time Jerk-limited Acceleration[J].Computer-aided Design,2004,36:27-36.
[9]CALLEJA A,TABERBERO I,EALO J A,et al.Feed Rate Calculation Algorithm for the Homogeneous Material Deposition of Blisk Blades by 5-axis Laser Cladding[J].International Journal of Advanced Manufacturing Technology,2014,74:1219-1228.
[10]李永桥,谌永祥,陈强,等.关于后置处理器设计中进给速度处理方法的研究[J].机床电器,2010(3):10-12.LI Yong-qiao,CHEN Yong-xiang,CHEN Qiang,et al.Research on Processing Method of Feed Rate in Designing the System of Post Processor[J].Machine Tool Electric Apparatus,2010(3):10-12.
[11]周瑞红,成群林,穆英娟,等.基于Pro/E的多轴联动数控加工进给速度控制技术研究[J].工艺与检测,2009(1):123-125.ZHOU Rui-hong,CHENG Qun-lin,MU Ying-juan,et al.Research on Feed-rate Control for Multi-axis CNC Machining Technology based on Pro/E[J].Technology and Test,2009(1):123-125.
[12]赵国勇,赵玉刚,赵庆志.数控运动中加加速度连续的加减速度[J].计算机集成制造系统,2011,17(2):316-320.ZHAO Guo-yong,ZHAO Yu-gang,ZHAO Qing-zhi.Acceleration&Deceleration Approach Based on Continuous Jerk in CNC Motion[J].Computer Integrated Manufacturing Systems,2011,17(2):316-320.
[13]SUN Yu-wen,BAO Yu-rong.A Cutter Orientation Modification Method for Five-axis Ball-end Machining with Kinematic Constraints[J].International Journal of Advanced Manufacturing Technology,2013,67(1):2863-2874.
[14]CHEN K H.Investigation of Tool Orientation For Milling Blade of Impeller in Five-axis Machining[J].International Journal of Advanced Manufacturing Technology,2011,52(5):235-244.
[15]CHEN H P,KUO H H,TSAY D M.Removing Tool Marks of Blade Surfaces by Smoothing Five-axis Point Milling Cutter Paths[J].Journal of Materials Processing Technology,2009,209:5810-5817.
[2]吴大中,王宇晗,冯景春,等.五坐标数控加工的非线性运动误差分析与控制[J].上海交通大学学报,2007,41(10):1608-1612.WU Da-zhong,WANG Yu-han,FENG Jing-chun,et al.Analysis and Control of the Nonlinear Errors in Five-axis NC Machining[J].Journal of Shanghai Jiao Tong University,2007,41(10):1608-1612.
[3]杨旭静,周元生,陈泽忠,等.五轴数控加工中旋转轴运动引起的非线性误差分析与控制[J].机械工程学报,2012,48(3):140-146.YANG Xu-jing,ZHOU Yuan-sheng,CHEN Ze-zhong,et al.Analysis and Control of Tool Path Interpolation Error in Rotary Axes Motions of Five-axis CNC Milling[J].Journal of Mechanical Engineering,2012,48(3):140-146.
[4]GASSARA B,BAILI M,DESSEIN G,et al.Feed Rate Modeling in Circular-Circular Interpolation Discontinuity for High-speed Milling[J].International Journal of Advanced Manufacturing Technology,2010,65:1619-1634.
[5]RIDWAN F,XU Xun,FREDERICK C L.Adaptive Execution of an NC Program with Feed Rate Optimization[J].International Journal of Advanced Manufacturing Technology,2010,63:1117-1130.
[6]GRAY P,BEDI S,ISMAIL F,et al.Comparison of 5-axis and 3-axis Finish Machining of Hydroforming Die Inserts[J].International Journal of Advanced Manufacturing Technology,2001,17(8):562-569.
[7]BEUDAERT X,PECHARD P,TOURNIER C.5-axis Tool Path Smoothing Based on Drive Constraints[J].International Journal of Machine Tools&Manufacture,2011,51(12):958-965.
[8]NAM S H,YANG M Y.A Study on a Generalized Parametric Interpolator with Real-time Jerk-limited Acceleration[J].Computer-aided Design,2004,36:27-36.
[9]CALLEJA A,TABERBERO I,EALO J A,et al.Feed Rate Calculation Algorithm for the Homogeneous Material Deposition of Blisk Blades by 5-axis Laser Cladding[J].International Journal of Advanced Manufacturing Technology,2014,74:1219-1228.
[10]李永桥,谌永祥,陈强,等.关于后置处理器设计中进给速度处理方法的研究[J].机床电器,2010(3):10-12.LI Yong-qiao,CHEN Yong-xiang,CHEN Qiang,et al.Research on Processing Method of Feed Rate in Designing the System of Post Processor[J].Machine Tool Electric Apparatus,2010(3):10-12.
[11]周瑞红,成群林,穆英娟,等.基于Pro/E的多轴联动数控加工进给速度控制技术研究[J].工艺与检测,2009(1):123-125.ZHOU Rui-hong,CHENG Qun-lin,MU Ying-juan,et al.Research on Feed-rate Control for Multi-axis CNC Machining Technology based on Pro/E[J].Technology and Test,2009(1):123-125.
[12]赵国勇,赵玉刚,赵庆志.数控运动中加加速度连续的加减速度[J].计算机集成制造系统,2011,17(2):316-320.ZHAO Guo-yong,ZHAO Yu-gang,ZHAO Qing-zhi.Acceleration&Deceleration Approach Based on Continuous Jerk in CNC Motion[J].Computer Integrated Manufacturing Systems,2011,17(2):316-320.
[13]SUN Yu-wen,BAO Yu-rong.A Cutter Orientation Modification Method for Five-axis Ball-end Machining with Kinematic Constraints[J].International Journal of Advanced Manufacturing Technology,2013,67(1):2863-2874.
[14]CHEN K H.Investigation of Tool Orientation For Milling Blade of Impeller in Five-axis Machining[J].International Journal of Advanced Manufacturing Technology,2011,52(5):235-244.
[15]CHEN H P,KUO H H,TSAY D M.Removing Tool Marks of Blade Surfaces by Smoothing Five-axis Point Milling Cutter Paths[J].Journal of Materials Processing Technology,2009,209:5810-5817.