等倾角螺旋槽铣削加工失效分析及装备方案研究
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摘要
等倾角螺旋槽是液体火箭发动机冷却通道的典型形式之一,其加工是航天制造领域的一项关键技术。我国当前采用的双盘铣刀、四轴联动铣削加工方法,存在铣削刀具干涉严重、铣头结构刚度不足、回转台精度保持性差等问题,影响着螺旋槽的加工精度,严重时会导致加工失效。因此,有必要对等倾角螺旋槽加工失效的因素进行系统分析,并研究一种螺旋槽加工装备的新的结构方案。
本文在等倾角螺旋槽双盘铣刀四轴联动加工的基础上,分析双盘铣刀铣削时刀具干涉产生的原因及其对螺旋槽形状精度的影响、铣头刚度不足引起的弹性变形对等倾角螺旋槽加工的影响。研究蜗轮蜗杆副的齿面接触应力和磨损和蜗杆副的消隙结构,选择将蜗杆分为蜗杆轴与空心蜗杆的双蜗杆结构来减小传动间隙,采用预测蜗杆副间隙调整时间的方法,来提高回转台精度。
研究等倾角螺旋槽的立铣刀五轴联动加工方法,选择刀具、确定主轴转速并制定加工工艺路线。通过立铣刀在铜板上的铣槽实验,验证立铣刀加工螺旋槽的可行性,分析立铣刀加工的切削参数、加工精度和效率等。分析立铣刀铣削加工等倾角螺旋槽的优点,以及方案实施的难点。
通过采用改变B轴位置、更换铣头结构、引入龙门结构、改变喷管装夹方式等方法,解决FA80G/1数控仿形铣床结构在等倾角螺旋槽加工中存在的问题。研究了双盘铣刀铣削和立铣刀铣削加工数控铣床的结构,确定新铣床的结构为单立柱式床身、工件立式装夹,并采用双摆铣头、双电机消隙回转台等结构。
分析数控铣床的静动态特性,在ANSYS workbench中对数控铣床的床身和铣头结构进行静力分析、模态分析及谐响应分析。分析了铣床主要结构的静刚度、固有频率,以及等倾角螺旋槽双盘铣刀铣削加工时铣床床身和铣头的共振频率,以及回转台结构的承载能力和定位精度。
等倾角螺旋槽的加工失效因素、立铣刀铣削方式、数控铣床结构的研究对提高火箭发动机等倾角螺旋槽的加工水平具有积极意义。
Loxodrome groove is one of the typical cooling channels of liquid rocket engine, Loxodrome grooves'processing is a key technique in aerospace manufacturing area. In our country, the scheme with double disc-mill cutter and four-axis linkage are adopted to process loxodrome groove of rocket nozzle. However, there are some problems in process of loxodrome, such as cutter interference of milling, low rigidity of milling head, low retentivity of B axis rotary table's accuracy and so on, which affect the process precision of loxodrome grooves and even lead to machining failure. Therefore, it is necessary to system analysis the factors that lead to machining failure of loxodrome grooves, and research a new structure scheme of processing equipment.
On the basis of machining with double disc-mill cutter and four-axis linkage, the reason for cutter interference and its effect on loxodrome groove's shape precision are explored, and the influence on loxodrome groove's machining by elastic deformation of milling head because of low rigidity is researched. The contact stress of worm gear pair and wear on the surface of worm's teeth are analyzed and various worm pairs with anti-backlash structure are studied. Double worm anti-backlash structure with worm shaft and hollow worm is adopted to decrease transmission backlash, and a time-adjusting forecasting method for worm gear is adopted to increase the positioning accuracy of axis rotary table.
Processing method for loxodrome grooves by five-axis linkage using end mill is discussed with tool type selected, spindle speed chosen and processing technique drafted. Through milling experiments on copper, the feasibility of processing with end milling cutter are verified, cutting parameters, machining accuracy and efficiency of the mill processing are researched. Merits of machining with end mill as well as the difficulties in processing loxodrome grooves are analyzed.
The location of B-axis is transformed, milling heads'structure are replaced and the gantry structure is introduced to solve problems in processing loxodrome grooves on FA80G/1 CNC copy milling machine. The structures of CNC milling machine with double disc-mill cutter and end mill are researched respectively. Single-column machine bed, vertical clamping, double pendulum milling head and dual-motor anti-backlash rotary table are adopted in the new milling machine structure.
The static and dynamic characteristics of CNC milling machine are analyzed using ANSYS workbench, including static analysis of the machine bed and milling head structure, modal analysis and harmonic analysis. The static structure stiffness and natural frequency are calculated; meanwhile the resonance frequency of the machine bed, the milling head in processing and the load capacity and positioning accuracy of rotary table is analyzed.
The research on the machining failure factors, milling method by end mill, and structure of CNC milling machine is of great significance to improve the processing performence of loxodrome groove.
本文在等倾角螺旋槽双盘铣刀四轴联动加工的基础上,分析双盘铣刀铣削时刀具干涉产生的原因及其对螺旋槽形状精度的影响、铣头刚度不足引起的弹性变形对等倾角螺旋槽加工的影响。研究蜗轮蜗杆副的齿面接触应力和磨损和蜗杆副的消隙结构,选择将蜗杆分为蜗杆轴与空心蜗杆的双蜗杆结构来减小传动间隙,采用预测蜗杆副间隙调整时间的方法,来提高回转台精度。
研究等倾角螺旋槽的立铣刀五轴联动加工方法,选择刀具、确定主轴转速并制定加工工艺路线。通过立铣刀在铜板上的铣槽实验,验证立铣刀加工螺旋槽的可行性,分析立铣刀加工的切削参数、加工精度和效率等。分析立铣刀铣削加工等倾角螺旋槽的优点,以及方案实施的难点。
通过采用改变B轴位置、更换铣头结构、引入龙门结构、改变喷管装夹方式等方法,解决FA80G/1数控仿形铣床结构在等倾角螺旋槽加工中存在的问题。研究了双盘铣刀铣削和立铣刀铣削加工数控铣床的结构,确定新铣床的结构为单立柱式床身、工件立式装夹,并采用双摆铣头、双电机消隙回转台等结构。
分析数控铣床的静动态特性,在ANSYS workbench中对数控铣床的床身和铣头结构进行静力分析、模态分析及谐响应分析。分析了铣床主要结构的静刚度、固有频率,以及等倾角螺旋槽双盘铣刀铣削加工时铣床床身和铣头的共振频率,以及回转台结构的承载能力和定位精度。
等倾角螺旋槽的加工失效因素、立铣刀铣削方式、数控铣床结构的研究对提高火箭发动机等倾角螺旋槽的加工水平具有积极意义。
Loxodrome groove is one of the typical cooling channels of liquid rocket engine, Loxodrome grooves'processing is a key technique in aerospace manufacturing area. In our country, the scheme with double disc-mill cutter and four-axis linkage are adopted to process loxodrome groove of rocket nozzle. However, there are some problems in process of loxodrome, such as cutter interference of milling, low rigidity of milling head, low retentivity of B axis rotary table's accuracy and so on, which affect the process precision of loxodrome grooves and even lead to machining failure. Therefore, it is necessary to system analysis the factors that lead to machining failure of loxodrome grooves, and research a new structure scheme of processing equipment.
On the basis of machining with double disc-mill cutter and four-axis linkage, the reason for cutter interference and its effect on loxodrome groove's shape precision are explored, and the influence on loxodrome groove's machining by elastic deformation of milling head because of low rigidity is researched. The contact stress of worm gear pair and wear on the surface of worm's teeth are analyzed and various worm pairs with anti-backlash structure are studied. Double worm anti-backlash structure with worm shaft and hollow worm is adopted to decrease transmission backlash, and a time-adjusting forecasting method for worm gear is adopted to increase the positioning accuracy of axis rotary table.
Processing method for loxodrome grooves by five-axis linkage using end mill is discussed with tool type selected, spindle speed chosen and processing technique drafted. Through milling experiments on copper, the feasibility of processing with end milling cutter are verified, cutting parameters, machining accuracy and efficiency of the mill processing are researched. Merits of machining with end mill as well as the difficulties in processing loxodrome grooves are analyzed.
The location of B-axis is transformed, milling heads'structure are replaced and the gantry structure is introduced to solve problems in processing loxodrome grooves on FA80G/1 CNC copy milling machine. The structures of CNC milling machine with double disc-mill cutter and end mill are researched respectively. Single-column machine bed, vertical clamping, double pendulum milling head and dual-motor anti-backlash rotary table are adopted in the new milling machine structure.
The static and dynamic characteristics of CNC milling machine are analyzed using ANSYS workbench, including static analysis of the machine bed and milling head structure, modal analysis and harmonic analysis. The static structure stiffness and natural frequency are calculated; meanwhile the resonance frequency of the machine bed, the milling head in processing and the load capacity and positioning accuracy of rotary table is analyzed.
The research on the machining failure factors, milling method by end mill, and structure of CNC milling machine is of great significance to improve the processing performence of loxodrome groove.
引文
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[2]Vadim Zakirovl, Vladimir Pavshook. Russian Nuclear Rocket Engine Design for Mars Exploration[J]. Tsinghua Science and Technology,2007,12(3):256-260.
[3]金韶山.液体火箭发动机推进室及钝体头锥发汗冷却研究[D].北京：清华大学,2008.
[4]ToddNeill, DonaldJudd, EricVeith et al. Practical uses of liquid methane in rocket engine applications [J]. ACTA ASTRONAUTICA,2009,65:696-705.
[5]范金.火箭发动机喷管螺旋槽数控自动编程及加工方法的研究[D].大连：大连理工大学,1999.
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[16]唐淳.变倾角变导程螺旋槽的数学建模和加工方法[D].大连：大连理工大学,2006.
[17]任秉根,刘华明,唐余勇.螺旋桨叶片曲面数控加工几何模型研究[J].哈尔滨工业大学学报,1999,31(4)：84-87.
[18]刘鸪然,王武东,徐建辉等.五轴联动数控铣床高效加工螺旋浆曲面[J].机电设备,2005,22(1)：41-43.
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[20]C.C. Lo. CNC machine tool surface interpolator for ball-end milling of freedom surface [J]. International Journal of Machine Tool & Manufacture,2000,40(3):307-326.
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[22]ShiPL, WangW, TangYY. Research on mathematical mode in manufacturing of ball end mills[J]. Chinese Journal of Mechanical Engineer,1994,30(5):55-59.
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[2]Vadim Zakirovl, Vladimir Pavshook. Russian Nuclear Rocket Engine Design for Mars Exploration[J]. Tsinghua Science and Technology,2007,12(3):256-260.
[3]金韶山.液体火箭发动机推进室及钝体头锥发汗冷却研究[D].北京：清华大学,2008.
[4]ToddNeill, DonaldJudd, EricVeith et al. Practical uses of liquid methane in rocket engine applications [J]. ACTA ASTRONAUTICA,2009,65:696-705.
[5]范金.火箭发动机喷管螺旋槽数控自动编程及加工方法的研究[D].大连：大连理工大学,1999.
[6]液压仿形铣槽机操作手册.武汉机床厂.1995.
[7]胡力耘.火箭大喷管数控仿形数字化加工系统的理论技术研究与设计[D].大连：大连理工大学,1998.
[8]卢杰持,胡力耘,杨金奎等.火箭大喷管数控仿形铣槽控制系统[J].大连理工大学学报,1998,38(3)：296-299.
[9]王永青,卢杰持,王春.大型航天火箭喷管铣槽加工系统[J].组合机床与自动化加工技术,2000(10)：25-27.
[10]范金,王永青,卢杰持.火箭发动机喷管螺旋槽加工方法的研究[J].大连理工大学学报.1999,39(3)：420-424.
[11]王学根.火箭喷管螺旋槽数控加工专用自动编程系统[D].西安：西北工业大学硕士论文,2002.
[12]范振云.液体火箭发动机喷管收扩段的数控加工工艺研究[J].宇航学报,2002,23(1)：87-90.
[13]王永青,卢杰持.等倾角螺旋槽的片铣刀铣削加工技术[J].工具技术,2002,36(8)：32-36.
[14]WANG Yong-qing, LU Jie-chi, TONG Yu. Technology of loxodrome coolant channel machining on liquid rocket engine[J]. Journal of Astronautics,2003,24(3):322-326.
[15]王永青,范金,卢杰持等.火箭喷管等倾角螺旋槽铣削加工中刀具干涉分析[J].大连理工大学学报,2001,41(5)：595-597.
[16]唐淳.变倾角变导程螺旋槽的数学建模和加工方法[D].大连：大连理工大学,2006.
[17]任秉根,刘华明,唐余勇.螺旋桨叶片曲面数控加工几何模型研究[J].哈尔滨工业大学学报,1999,31(4)：84-87.
[18]刘鸪然,王武东,徐建辉等.五轴联动数控铣床高效加工螺旋浆曲面[J].机电设备,2005,22(1)：41-43.
[19]TangYY. General mathematical code for grinding of precise helicoid[J]. Chinese journal of mechanical engineering.1991,27(3):32-37.
[20]C.C. Lo. CNC machine tool surface interpolator for ball-end milling of freedom surface [J]. International Journal of Machine Tool & Manufacture,2000,40(3):307-326.
[21]LiuKexinB C. Helicoid theory for design of cutting tools[M]. Bingjing: Publish House of Mechanical Industry,1984,5-20.
[22]ShiPL, WangW, TangYY. Research on mathematical mode in manufacturing of ball end mills[J]. Chinese Journal of Mechanical Engineer,1994,30(5):55-59.
[23]张辉,姚南询等.等倾角回转刀具刀刃曲线的通用算法[J],大连理工大学学报,1997,37(1)：63-67.
[24]D.S.Sheth et al. CAD/CAM for Geometry and Process Analysis of Helical Groove Machining[J]. Annals of the CIRP,1991,39(1):129-132.
[25]S. Kaldor, Ada Mod Rafeal, D. Messinger. On the CAD of Profiles for Cutters and Helical Flutes-Geometrical Aspects. Annals of CIRP,1998,37(1):53-57.
[26]李园.基于西门子SINUMERIK 802S的CA6140车床数控化改造[D].杭州：浙江工业大学,2007.
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