Analysis and Optimal Design of Fixture Clamping Sequence

Considering the great impacts of the application sequence of multiclamps on the workpiece machining accuracy, this paper analyzes and optimizes clamping sequence. A new methodology that takes into account the varying contact forces and friction force during clamping is presented for the first time. A new analysis model is established to capture the effect of clamping sequence on contact force distributions and workpiece machining accuracy. It reveals that the historical accumulation of clamping steps influences heavily the final distribution of contact forces in the workpiece-fixture system. Therefore, the present contact forces in each clamping step are solved incrementally in terms of contact forces of the precedent step by means of the principle of the total complementary energy. Furthermore, based on the fact that the variation of contact forces from one step to another results in different workpiece deformations and position, a novel design model is formulated to select optimally the clamping sequence in order to minimize the workpiece deformation and position errors. Workpieces of low stiffness and high stiffness are investigated separately in order to simplify the modeling of clamping sequence optimization. Some numerical tests are finally demonstrated to validate the proposed model and method. Computational results are discussed and compared with experimental results available in the reference.

[1]  W. R. DeVries,et al.  Finite element analysis and optimization in fixture design , 1999 .

[2]  Shreyes N. Melkote,et al.  Analysis of the effects of fixture clamping sequence on part location errors , 2004 .

[3]  E. C. DeMeter,et al.  Restraint Analysis of Fixtures Which Rely on Surface Contact , 1994 .

[4]  H. Harry Asada,et al.  Kinematic analysis and planning for form closure grasps by robotic hands , 1989 .

[5]  Shreyes N. Melkote,et al.  An Elastic Contact Model for the Prediction of Workpiece-Fixture Contact Forces in Clamping , 1999 .

[6]  Jonathan W. Lee,et al.  Finite-Element Analysis of Flexible Fixturing System , 1987 .

[7]  S. Jack Hu,et al.  A Variational Method of Robust Fixture Configuration Design for 3-D Workpieces , 1997 .

[8]  H. Harry Asada,et al.  Kinematic analysis of workpart fixturing for flexible assembly with automatically reconfigurable fixtures , 1985, IEEE J. Robotics Autom..

[9]  Yunhui Liu,et al.  Force passivity in fixturing and grasping , 2003, 2003 IEEE International Conference on Robotics and Automation (Cat. No.03CH37422).

[10]  K. Johnson.  Contact Mechanics: Frontmatter , 1985 .

[11]  Shreyes N. Melkote,et al.  Fixture Clamping Force Optimisation and its Impact on Workpiece Location Accuracy , 2001 .

[12]  Andrew Y. C. Nee,et al.  Modeling of Frictional Elastic Fixture–Workpiece System for Improving Location Accuracy , 1996 .

[13]  Weihong Zhang,et al.  A mathematical approach to analysis and optimal design of a fixture locating scheme , 2006 .

[14]  Jingxia Yuan,et al.  Deformable Sheet Metal Fixturing: Principles, Algorithms, and Simulations , 1996 .

[15]  Michael Yu Wang,et al.  On Prediction of Passive Contact Forces of Workpiece-Fixture Systems , 2003 .

[16]  Martin W. Trethewey,et al.  A model to predict minimum required clamp pre-loads in light of fixture–workpiece compliance , 2001 .

[17]  Michael Yu Wang,et al.  Contact Force Prediction and Force Closure Analysis of a Fixtured Rigid Workpiece With Friction , 2003 .

[18]  Warren R. DeVries,et al.  Optimization Methods Applied to Selecting Support Positions in Fixture Design , 1991 .

[19]  Y.J.Gene Liao,et al.  Flexible multibody dynamics based fixture-workpiece analysis model for fixturing stability , 2000 .

[20]  Jerry Y. H. Fuh,et al.  An integrated fixture planning and analysis system for machining processes , 1993 .

[21]  José F. Hurtado,et al.  Modeling and Analysis of the Effect of Fixture-Workpiece Conformability on Static Stability , 2002 .

[22]  W. Wunderlich,et al.  Mechanics of Structures. Variational and Computational Methods , 1993 .

[23]  Tsuneo Yoshikawa.  Passive and Active Closures by Constraining Mechanisms , 1999 .

[24]  Joel W. Burdick,et al.  Passive force closure and its computation in compliant-rigid grasps , 2001, Proceedings 2001 IEEE/RSJ International Conference on Intelligent Robots and Systems. Expanding the Societal Role of Robotics in the the Next Millennium (Cat. No.01CH37180).

[25]  Shreyes N. Melkote,et al.  Iterative Fixture Layout and Clamping Force Optimization Using the Genetic Algorithm , 2000, Manufacturing Engineering.

[26]  Y. Kang,et al.  Computer‐aided fixture design verification , 2002 .

[27]  C. Cogun.  The Importance of the Application Sequence of Clamping Forces on Workpiece Accuracy , 1992 .

[28]  M. M. Barash,et al.  A Mathematical Approach to Automatic Configuration of Machining Fixtures: Analysis and Synthesis , 1989 .