Gasbag Precession Polishing Technique and Its Realization on Curved Surface Mould
|School||Zhejiang University of Technology|
|Course||Mechanical and Electronic Engineering|
|Keywords||mould gasbag precession time-varying material removal characteristic feedrate initial posture deflection angle trajectory optimization|
In order to improve the precision and quality of the mould, polishing is necessary in the mould manufacturing process. Well, with the products become personalized and refined, curved design and application is more and more and processing difficult relatively improve. At present, curved surface mould polishing is mainly manual with low production efficiency and unstable polishing quality. This makes polishing become the biggest bottleneck in the automated mould polishing.Focusing on the crux and hot topic of polishing curved surface mould and combing the research supported by the National Natural Science Foundation of China (No.50575208), a novel curved surface mould polishing with contimuous precession process technique is proposed based on the gasbag polishing tool. This kind of technique is based on compliant contact between controllable flexibility gasbag polishing tool and mould free-from surface and the polishing tool pose and path planning control, which guarantees the local surface shape amendment precision and the quality of curved surface. The efficiency, accuracy and automation of polishing can be realized.Main works of this dissertation are shown as follows:1) The time-varying material removal characteristic of gasbag polishing with continuous precession process is analyzed. Comparative study of the principle and effect of the gasbag polishing with continuous precession process and without continuous precession process is carried out. The gasbag sentinel precession and continuous precession are analyzed and laid a theoretical foundation for the polishing tool to achieve continuous precession in the robot control. The abrasive movement trend, distribution state, mechanism of action and time-varying characteristics of the polishing with continuous precession process are researched through the experiments and simulation, which laid a foundation for time-varying material removal model, processing active control and trajectory optimization study. The time-varying material removal model is proposed based on the loss factor of abrasive group and a uniform removal of material is realized. The stable surface quality is obtained.2) The feed rate and initial posture deflection angle of gasbag polishing with continuous precession process are studied. The polishing contact force with different downward depth, inflation pressure and radius of curvature is researched through experiments, which provides the theoretical basis for the polishing contact force compensation experiments. The contact force and contact pressure’s uniformity orthogonal simulation and analysis are done for sensitivity sort and forecast the result with different downward depth, inflation pressure, angle, thickness and the rubber elastic modulus of the gasbag and provide the basis for the correct selection of the process parameters and gasbag. The influence of the equal wall thickness and unequal wall thickness gasbag to the contact force and the uniformity of pressure distribution are studied. Based on the velocity field research, the tangential velocity and the cutting direction expression are given. The feed rate and initial posture deflection angle are defined and the optimized combination method of the initial posture deflection angle is determined, which provide guarantee for the trajectory optimization study of the gasbag polishing with continuous precession process. Based on the analysis of the contact force, pressure distribution and velocity field, the material removal modeling idea is given and the material removal simulation is realized in the MATLAB environment.3) The trajectory optimization of the gasbag polishing with continuous precession process is studied. The process planning strategy, dwell time, feed rate and contact edge effect of gasbag polishing with continuous precession process are studied and analyzed. The cutting direction distribution and material removal characteristics are studied on the different precession ratio. The optimized precession ratio and the corresponding feed rate is given, which laid a foundation for optimize the stacking fold and line space. The material removal characteristic under different initial posture deflection angles stacking is analyzed and the optimized stacking fold is given. A binary optimization method of trajectory planning based on probability technology is proposed. The line space optimization problem is studied and the optimization value is given.4) The gasbag polishing precession system and the polishing process are studied. Establish the offline planning prototype system of the gasbag polishing with continuous precession process based on the study of the robot-assisted gasbag polishing with continuous precession process, which laid an important foundation for realizing the automation polishing and trajectory planning. The gasbag polishing contact force network control system is designed based on LabVIEW. It can realize the forecast of gasbag input pressure and the control of polishing contact force. The tracking characteristic of the gasbag polishing contact force control platform is verified through the tracking simulation and experiment of the contact force. The process experiment research of the gasbag continues precession is done and the ideal results are achieved based on the offline planning prototype system and the gasbag polishing contact force network control system.This dissertation has some significant theoretical guidance and technical reference value for propelling the development of polishing technology with high level of efficiency, accuracy and automation for curved surface mould.