摘要
零件的加工质量取决于机床、夹具、工件和刀具组成的工艺系统及加工工艺参数等因素。对特定的机床,当工艺参数选定之后,工件-夹具-刀具系统直接影响零件的加工质量。本论文以“工件-夹具-刀具”系统为研究对象,研究误差建模方法,在物理约束、几何约束与产品性能约束的相容性条件下,建立误差源与产品性能约束的映射关系、零件加工误差与工艺参数之间的反演模型,提出制造误差补偿与控制策略,为复杂零件高精度创成提供理论基础,主要研究工作及创新点包括：
第一、定位方案分析与评估
针对加工期望特征所必须确保的尺寸方向上的精度,从加工几何学的角度,建立特征约束度模型,确定工件在定位系统中约束自由度的数目,构建加工特征运动旋量系和加工特征约束度数表。利用运动学分析并结合虚位移原理,构造定位系统非齐次线性方程组的线性空间齐次解,判断与尺寸精度无关的自由度所约束的数目,推导判断定位方案正确性的准则,据此,提出基于加工特征的定位方案设计方法。
第二、定位误差分析评估与调整
针对工件在定位系统中的位移和刀具的位姿偏差共同诱导的刀具相对工件的位姿偏差,建立工件的位移、刀具的姿态偏差与刀具相对工件的位姿偏差的映射模型,此模型能够适用于任何形状工件的不完全定位、完全定位和完全过定位。在此基础之上,构建偏差反演模型,调整刀具相对工件的位姿,减小刀具相对工件之间的偏差,实现利用一种偏差补偿多种偏差的误差补偿技术,达到减小加工特征尺寸偏差的目的。
第三、装夹误差分析与刀具路径调整
针对多源多工序加工过程,建立几何偏差源与物理偏差源共同作用的尺寸偏差模型,该模型能够直接用于度量加工特征尺寸偏差。基于此模型,建立加工特征点的偏差模型,用于评估加工特征平行度和轮廓度。同时针对工件-夹具系统在夹紧力及切削力作用下的超静定系统,根据变形协调原理,建立变形协调模型,利用功能转换原理,将接触变形量的求解问题转化非线性规划问题,在几何与物理约束条件下,通过求解非线性规划问题获得定位元件与工件之间的接触变形量,并对加工过程中接触变形量的动态变化以予定量评估。此外,基于预测的偏差,建立刀具路径调整模型,用于修改CAM系统的刀位源文件,调整刀具的位姿,减小加工特征尺寸偏差。
第四、工件加工表面微观形貌预测
针对切削力诱导的工件和刀具的振动、工件在定位系统中的位移和工艺参数对表面形貌生成的影响,建立刀刃点在加工特征活动标架下的数学模型,该模型适用于平面和一般的直纹面。根据局部活动标架特征,将加工表面残高求解问题转化为非线性规划问题,通过求解非线性规划问题获得加工特征采样点的残高,利用采样点的残高值构造加工表面形貌,并计算粗糙度。此外,结合刀具齿数对刀具偏移的影响,利用lobe图选取薄壁型腔件的铣削工艺参数,提高铣削效率。
The quality of the machined part mainly depends on the complicated process system which consists of machine tools, fixture, workpiece, cutter and process parameters etc. At specific machine tools, once process parameters are selected, the machining quality of part depends on the performance of workpiece-fixture-cutter system. Therefore, in this paper, workpeice-fixture-cutter is taken as the investigated subject so that the rules of error propogration and prediction methods can be found out. Specific work includes following four aspects:
(1). Location scheme design based on the machining feature
A machining feature requirement driven workpiece holding scheme is proposed to constrain the degrees of freedom (DOFs) of the workpiece. In the locating scheme, the machining feature on workpiece is used to determine those DOFs which have to be constrained in machining. And then a kinematic model is used to determine the number of the constrained DOFs in a real locating scheme. By means of kinematics and the virtual displacement principle, Homogeneous solution of the linear space of non-homogeneous linear equations of location system is constructed to determine the number of the constrained DOFs of the workpiece which are unrelated to dimensional accuracy. Finally, an evaluation criterion is given to judge the correctness of the locating scheme.
(2). Dimension devation evaluation and adjustment of the machining feature
A model is built to integrate position and orientation errors of cutter and workpiece displacement into the relative displacement of the cutter with respect to the workpiece by means of the differential motion theory. Based on the model, a deviation adjustment model is constructed to adjust the position and orientation of the workpiece with respect to the cutter in order that the machining accuracy of workpiece can be improved. Therefore, a compensation technique which can utilize one error source to cancel out multiple error sources is proposed. Three examples are used to validate the feasibility of the proposed models.
(3). Dimensional deviation propagation model and adjustment model
In multi-source multi-processing machining operations, a machining feature from a previous machining operation is taken as the machining datum at the current machining operation. The devation from upstream will be accumulated on the current machining feature. Therefore, a comprehensive dimensional deviation evaluation framework is developed which it can be utilized to predict process deviation. At the same time, in order to obtain the displacement of workpiece due to the geometric defects of workpiece-fixture sytem, cutting forces and fixturing forces, the solution problem of contact deformation between the fixture elements and workpiece is transformed into a nonlinear programming, and solve the nonlinear programming under geometric and physical constraints and obtain the deformation magnigudes. In addition, the dynamic changing process of the deformation is evaluated in machining processs. Based on the predicted deviation, a model is built to adjust the tool path by means of the cutter source file from CAM in order that the machining accuracy of the machining feature can be improved.
(4). Surface topography prediction.
A general kinematic model which integrates the deflection of the cutting tools with respect to workpiece caused by cutting force and process parameters into one model is presented to build kinematic relationship between the arbitrary point of the cutter edge and the arbitrary point of the machining feature. According to the properties of moving frame, the solution problem of the machining surface scallop is transformed into a nonlinear programming problem. By means of solving the nonlinear programming problem, these scallops along the normals of nominal surface can be obtained, and then construct the surface topography and calculate the roughness values. At the same time, the stability lobe figure is constructed to select the process parameters for machining thin-walled cavity parts. Finally, the planar surface and circular arc surface texture are simulated by means of calculating a scallop value along a normal direction of an arbitrary point on nominal part surface in terms of the proposed model, three dimension profile can also be simulated. The feasibility of the proposed models is verified.
引文
[1]杨叔子,吴波,李斌,再论先进制造技术及发展趋势.机械工程学报42(2006)1-5.
[2]H. Asada, A. By, Kinematic analysis of workpart fixturing for flexible assembly with automatically reconfigurable fixtures, IEEE, Robotics and Automation,1985, 1(2):86-94.
[3]Y. Chou, V. Chandru, M. Barash, A mathematical approach to automatic configuration of machining fixtures,analysis and synthesis, Transactions of the ASME, Journal of Engineering for Industry,1989,111(4):299-306.
[4]B. Li, S. Melkote, Improved workpiece location accuracy through fixture layout optimization. International Journal of Machine Tools and Manufacture,1999, 39(6):871-883.
[5]M. Wang, T. Liu, D. Pelinescu, Fixture kinematic analysis based on the full contact model of rigid bodies, Transactions of the ASME, Journal of Manufacturing Science and Engineering,2003,125(2):316-324.
[6]J. Carlson, Quadratic sensitivity analysis of fixtures and locating schemes for rigid parts, Transactions of the ASME, Journal of Manufacturing Science and Engineering,2001,123(3):462-472.
[7]R. Marin, P. Ferreira, Kinematic analysis and synthesis of deterministic 3-2-1 locator schemes for machining fixtures, Transactions of the ASME, Journal of Manufacturing Science and Engineering,2001,123(4):708-719.
[8]Y. Kang, Y. Rong, J. Yang, Computer-Aided Fixture Design Verification. Part 1. The Framework and Modelling, The International Journal of Advanced Manufacturing Technology,2003,21(10-11):827-835.
[9]C. H. Xiong, Y. Li, Y. Kevin Rong, Y. L. Xiong, Qualitative analysis and quantitative evaluation of fixturing. Robotics and Computer Integrated Manufacturing,2002,18(5-6):335-342.
[10]C. H. Xiong, M. Y. Wang, Y. Tang, Y. L. Xiong, On clamping planning in workpiece-fixture systems, IEEE Transactions on Automation Science and Engineering,2008,5(3):407-419.
[11]C. H. Xiong, Y. L.Xiong, M. Y. Wang, Clamping planning in workpiece-fixture systems, Proceedings of the ASME Manufacturing Engineering Division,2003, 14:267-272.
[12]C. H. Xiong, M. Y. Wang, Y. Tang, Y. L.Xiong, On the prediction of passive
contact forces of workpiece-fixture systems. Proceedings of the Institution of Mechanical Engineers, Part B:Journal of Engineering Manufacture,2005,219(3): 309-324.
[13]C. H. Xiong, An approach to error elimination for multi-axis CNC machining and robot manipulation. Science in China Series E:Technological Sciences,2007, 50(5):560-574.
[14]N. Wu, K. Chan, S. Leong, Static interactions of surface contacts in a fixture-workpiece system, International Journal of Computer Applications in Technology,1997,10(3-4):133-151.
[15]G Shawki, M. Abdel-Aal, Effect of fixture rigidity and wear on dimensional accuracy. International Journal of Machine Tool Design and Research,1965, 5(3):183-202.
[16]M. Ohwovoriole, B. Roth, An extension of screw theory. Transactions of the ASME, Journal of Mechanical Design,1981,103 (4):725-735.
[17]W. Cai, S. Hu, J. Yuan, A variational method of robust fixture configuration design for 3-D workpieces, Transactions of the ASME, Journal of Manufacturing Science and Engineering,1997,119(4A):593-602.
[18]Y. Zhang, W. Hu, Y. Rong, D. Yen, Graph-based set-up planning and tolerance decomposition for computer-aided fixture design, International Journal of Production Research,2001,39 (14):3109-3126.
[19]Y. Rong, Y. Zhu, Computer-aided fixture design, CRC,1999.
[20]R. Marin, P. Ferreira, Analysis of the influence of fixture locator errors on the compliance of work part features to geometric tolerance specifications, Transactions of the ASME,Journal of Manufacturing Science and Engineering, 2003,125(3):609-616.
[21]S. Choudhuri, E. De Meter, Tolerance analysis of machining fixture locators, Transactions of the ASME, Journal of Manufacturing Science and Engineering, 1999,121(2):273-281.
[22]Y. Kang, Y. Rong, J. Yang, Computer-aided fixture verification, Part 2, Tolerance analysis, The International Journal of Advanced Manufacturing Technology,2003, 21(10-11):836-841.
[23]M. Wang, An optimum design for 3-D fixture synthesis in a point set domain. IEEE Transactions on Robotics and Automation,2000,16(6):839-846.
[24]Y. Rong, Y. Bai, Machining accuracy analysis for computer-aided fixture design verification, Transactions of the ASME, Journal of Manufacturing Science and Engineering,1996,118(3):289-300.
[25]E. Salisbury, F. Peters, The impact of surface errors on fixtured workpiece location
and orientation. Transactions-NorthT American Manufacturing Reseach Institution of SME,1998,323-328.
[26]Z. Tao, S. Kumar, Modelling and experimental investigation of a sensor-integrated workpiece-fixture system, International Journal of Computer Applications in Technology,1997,10(3-4):236-250.
[27]J. Lee, L. Haynes, Finite-element analysis of flexible fixturing system, Transactions of the ASME, Journal of Engineering for Industry,1987, 109(2):134-139.
[28]Y. Liao, S. Hu, Flexible multibody dynamics based fixture-workpiece analysis model for fixturing stability, International Journal of Machine Tools and Manufacture,2000,40(3):343-362.
[29]M. Hockenberger, E. De Meter, The effect of machining fixture design parameters on workpiece displacement. Manufacturing Review,1995,8:22-32.
[30]R. Menassa, W. DeVries, Optimization methods applied to selecting support positions in fixture design. Journal of Engineering for Industry,1991, 113(4):412-418.
[31]E. DeMeter, Min-max load model for optimizing machining fixture performance. J. Eng. Industry,1995,117(1):186-193.
[32]B. Li, S. Melkote, Fixture clamping force optimisation and its impact on workpiece location accuracy. The International Journal of Advanced Manufacturing Technology,2001,17(2):104-113.
[33]A. Raghu, S. Melkote, Analysis of the effects of fixture clamping sequence on part location errors. International Journal of Machine Tools and Manufacture,2004, 44(4):373-382.
[34]K. Krishnakumar, S. Melkote, Machining fixture layout optimization using the genetic algorithm. International Journal of Machine Tools and Manufacture,2000, 40(4):579-598.
[35]A. Raghu, S. Melkote, Modeling of workpiece location error due to fixture geometric error and fixture-workpiece compliance, Transactions of the ASME, Journal of Manufacturing Science and Engineering,2005,127(1):75-83.
[36]H. Deng, S. Melkote, Determination of minimum clamping forces for dynamically stable fixturing. International Journal of Machine Tools and Manufacture,2006, 46(7-8):847-857.
[37]S. Yang, J. Yuan, J. Ni, Real-time cutting force induced error compensation on a turning center. International Journal of Machine Tools and Manufacture,1997, 37(11):1597-1610.
[38]S. Chen, A. Ulsoy, Y. Koren, Error source diagnostics using a turning process
simulator, Transactions of the ASME,Journal of Manufacturing Science and Engineering,1998,120(2):409-416.
[39]J. Mayer, A. Phan, G. Cloutier, Prediction of diameter errors in bar turning:a computationally effective model. Applied Mathematical Modelling,2000, 24(12):943-956.
[40]S. Ratchev, S. Liu, W. Huang, A. Becker, An advanced FEA based force induced error compensation strategy in milling. International Journal of Machine Tools and Manufacture,2006,46(5):542-551.
[41]C. Raksiri, M. Parnichkun, Geometric and force errors compensation in a 3-axis CNC milling machine. International Journal of Machine Tools and Manufacture, 2004,44(12-13):1283-1291.
[42]彭芳瑜,李黎,陈徐兵,李斌,连续小直线段高速高精插补中的动力学约束条件.计算机辅助设计与图形学学报18(2006)1812-1816.
[43]毕运波,铣削加工过程物理模拟及其在航空整体结构件加工变形预测中的应用研究[博士学位论文],浙江大学,浙江,2007.
[44]胡创国,薄壁件精密切削变形控与误差补偿技术研究[博士学位论文],西北工业大学,西安,2007.
[45]万敏,薄壁件周铣加工过程中表面静态误差预测关键技术研究[硕士学位论文],西北工业大学,西安,2005.
[46]郭魂,航空多框整体结构件铣削变形机理与预测分析研究[博士学位论文],南京航空航天大学,南京,2005.
[47]V. Kreng, C. Liu, C. Chu, A kinematic model for machine tool accuracy characterisation. The International Journal of Advanced Manufacturing Technology, 1994,9(2):79-86.
[48]E. Lee, S. Suh, J. Shon, A comprehensive method for calibration of volumetric positioning accuracy of CNC-machines. The International Journal of Advanced Manufacturing Technology,1998,14(1):43-49.
[49]G. Chen, J. Yuan, J. Ni, A displacement measurement approach for machine geometric error assessment. International Journal of Machine Tools and Manufacture,2001,41(1):149-161.
[50]A. Okafor, Y. Ertekin, Derivation of machine tool error models and error compensation procedure for three axes vertical machining center using rigid body kinematics. International Journal of Machine Tools and Manufacture,2000, 40(8):1199-1213.
[51]J. Ni, S. Wu, An on-line measurement technique for machine volumetric error
compensation, Transactions of the ASME, Journal of Engineering for Industry, 1993,115(1):85-92.
[52]R. Ramesh, M. Mannan, A. Poo, Error compensation in machine tools-a review Part Ⅰ:geometric, cutting-force induced and fixture-dependent errors. International Journal of Machine Tools and Manufacture,2000,40(9):1235-1256.
[53]J. Lee, S. Yang, Statistical optimization and assessment of a thermal error model for CNC machine tools. International Journal of Machine Tools and Manufacture, 2002,42(1):147-155.
[54]C. Mize, J. Ziegert, Neural network thermal error compensation of a machining center. Precision Engineering,2000,24(4):338-346.
[55]J. Yang, J. Yuan, J. Ni, Thermal error mode analysis and robust modeling for error compensation on a CNC turning center. International Journal of Machine Tools and Manufacture,1999,39(9):1367-1381.
[56]C. Lo, J. Yuan, J. Ni, Optimal temperature variable selection by grouping approach for thermal error modeling and compensation. International Journal of Machine Tools and Manufacture,1999,39(9):1383-1396.
[57]F. Fuh, C. Chang, M. Melkanoff, An integrated fixture planning and analysis system for machining processes. Robotics and computer-integrated manufacturing, 1993,10(5):339-353.
[58]M. Hockenberger, E. De Meter, The application of meta functions to the quasi-static analysis of workpiece displacement within a machining fixture, Transactions of the ASME, Journal of Manufacturing Science and Engineering, 1996,118(3):325-331.
[59]B. Shiu, D. Ceglarek, J. Shi, Multi-stations sheet metal assembly modeling and diagnostics. Transactions-north american manufacturing research,SME, 1996:199-204.
[60]J. Lawless, R. Mackay, J. Robinson, Analysis of variation transmission in manufacturing processes-part Ⅰ. Journal of Quality Technology,1999, 31(2):131-142.
[61]R. Agrawal, J. Lawless, R. Mackay, Analysis of variation transmission in manufacturing processes-part Ⅱ. Journal of Quality Technology,1999, 31(2)143-154.
[62]J. Jin, J. Shi, State space modeling of sheet metal assembly for dimensional control, Transactions of the ASME, Journal of Manufacturing Science and Engineering, 1999,121(4):756-762.
[63]Y. Ding, D. Ceglarek, J. Shi, Modeling and diagnosis of multistage manufacturing processes:part Ⅰ state space model,2000,23-26.
[64]Y. Ding, D. Ceglarek, J. Shi, Fault diagnosis of multistage manufacturing processes by using state space approach, Transactions of the ASME, Journal of Manufacturing Science and Engineering,2002,124(2):313-322.
[65]Q. Huang, N. Zhou, J. Shi, Stream of variation modeling and diagnosis of multi-station machining processes. Ann Arbor 1001 48109-42117.
[66]W. Zhong, Y. Huang, S. Hu, Modeling variation propagation in machining systems with different configurations. Ann Arbor 1001 48109.
[67]D. Djurdjanovic, J. Ni, Linear state space modeling of dimensional machining errors. Transaction-north american manufacturing research institiution of sme, 2001,541-548.
[68]S. Zhou, Q. Huang, J. Shi, State Space Modeling of Dimensional Variation Propagation in Multistage Machining Process Using a Differential Motion Vector. IEEE Transactions on robotics and automation,2003,19(2):296-309.
[69]杜世昌,多源多工序加工系统偏差流建模、诊断和控制系统研究[博士学位论文],上海交通大学,上海,2008.
[70]赵家黎,基于SOV理论的过程质量控制方法研究[博士学位论文],天津大学,天津,2007.
[71]T. Jung, M. Yang, K. Lee, A new approach to analysing machined surfaces by ball-end milling, part Ⅱ. The International Journal of Advanced Manufacturing Technology,2005,25 (9-10):841-849.
[72]B. Imani, M. Sadeghi, M. Elbestawi, An improved process simulation system for ball-end milling of sculptured surfaces, International Journal of Machine Tools and Manufacture,1998,38(9):1089-1107.
[73]B. Imani, M. Elbestawi, Geometric simulation of ball-end milling operations. Journal of Manufacturing Science and Engineering, Transactions of the ASME, 2001,123(2):177-184.
[74]M. Sadeghi, H. Haghighat, M. Elbestawi, A solid modeler based ball-end milling process simulation. The International Journal of Advanced Manufacturing Technology,2003,22 (11-12):775-785.
[75]K. Bouzakis, P. Aichouh, K. Efstathiou, Determination of the chip geometry, cutting force and roughness in free form surfaces finishing milling, with ball end tools. International Journal of Machine Tools and Manufacture,2003, 43(5):499-514.
[76]K. Ehmann, M. Hong, A generalized model of the surface generation process in metal cutting. CIRP,1994,43(1):483-486
[77]I. Lazoglu, Sculpture surface machining:A generalized model of ball-end milling
force system. International Journal of Machine Tools and Manufacture,2003,43 (5): 453-462.
[78]A. Antoniadis, C. Savakis, N. Bilalis, A. Balouktsis, Prediction of surface topomorphy and roughness in ball-end milling, The International Journal of Advanced Manufacturing Technology,2003,21(5):965-971.
[79]T. Gao, W. Zhang, K. Qiu, M. Wan, Numerical simulation of machined surface topography and roughness in milling process, Transactions of the ASME, Journal of Manufacturing Science and Engineering,2006,128(1):96-103.
[80]W. H. Zhang, M. Wan, A new algorithm for the numerical simulation of machined surface topography in multiaxis ball-end milling, Transactions of the ASME, Journal of Manufacturing Science and Engineering,2008,130(1):1-11.
[81]S. Smith, J. Tlusty, An overview of modeling and simulation of the milling process, Transactions of the ASME, Journal of Engineering for Industry,1991, 113(2):169-175.
[82]W. Kline, R. DeVor, I. Shareef, The prediction of surface accuracy in end milling, Transactions of the ASME, Journal of Engineering for Industry,1982, 104(3):272-278.
[83]J. Sutherland, R. DeVor, An improved method for cutting force and surface error prediction in flexible end milling systems, Transactions of the ASME, Journal of Engineering for Industry,1986,108(4):269-279.
[84]S.Smith, J. Tlusty, NC programming for quality in milling, CIRP Annals-Manufacturing Technology,1988,39(1):517-521.
[85]D. Montgomery, Y. Atlintas, Mechanism of cutting force and surface generation in dynamic milling, Transactions of the ASME, Journal of Engineering for Industry,1991,113(9):160-168.
[86]F. Ismail, M. Elbestawi, R. Du, K. Urbasik, Generation of milled surfaces including tool dynamics and wear, Transactions of the ASME, Journal of Engineering for Industry,1993,115(3):245-252.
[87]E. Budak, Y. Altintas, Peripheral milling conditions for improved dimensional accuracy. International Journal of Machine Tools and Manufacture,1994, 34(7):907-918.
[88]E. Budak, Y. Altintas, Flexible milling force model for improved surface error predictions, American Society of Mechanical Engineers,1992,47(1):89-94.
[89]K. Shirase, Y. Altintas, Cutting force and dimensional surface error generation in peripheral milling with variable pitch helical end mills. International Journal of Machine Tools and Manufacture,1996,36(5):567-584.
[90]S. Ryu, H. Lee, C. Chu, The form error prediction in side wall machining
considering tool deflection. International Journal of Machine Tools and Manufacture,2003,43(14):1405-1411.
[91]A. Larue, B. Anselmetti, A prediction of the machining defects in flank milling. The International Journal of Advanced Manufacturing Technology,2004, 24(1-2):102-111.
[92]Y. Shin, A. Waters, Framework of a machining advisory system with application to face milling processes, Journal of Intelligent Manufacturing,1998,9(3):225-234.
[93]M. Elbestawi, F. Ismail, K. Yuen, Surface topography characterization in finish milling. International Journal of Machine Tools & Manufacture,1994, 34(2):245-255.
[94]张智海,铣削工艺系统瞬态力学模型和非线性动力学特性的研究,清华大学[博士学位论文],北京,2001.
[95]李成峰,介观尺度铣削力与表面形貌建模及工艺优化研究[博士学位论文],上海交通大学,上海,2008.
[96]C. H. Xiong, H. Ding, Y. Xiong, Fundamentals of robotic grasping and fixturing, World Scientific,2007.
[97]C. H. Xiong, Y. Rong, Y. Tang, Y. L. Xiong, Fixturing model and analysis. International Journal of Computer Applications in Technology,2007,28(1):34-45.
[98]D. Ceglarek, J. Shi, Dimensional variation reduction for automotive body assembly. Manufacturing Review 8 (1995).
[99]D. Ceglarek, W. Huang, S. Zhou, Y. Ding, R. Kumar, Y. Zhou, Time-based competition in multistage manufacturing:stream-of-variation analysis(SOVA) methodology-review. International Journal of Flexible Manufacturing Systems, 2004,16(1):11-44.
[100]K. Johnson, Contact mechanics, Cambridge Univ Pr,1987.
[101]E. DeMeter, Restraint analysis of fixtures which rely on surface contact, Transactions of the ASME, Journal of Engineering for Industry,1994,116 (2):207-215.
[102]K. Cheng, Machining Dynamics:Fundamentals, Applications and Practices, Springer Verlag,2008.