Gasbag Polishing Mechanism And Process On Free-form Surface Mould

Mould is an important basis for the development of manufacturing industry and has extensive application prospects in the fields of machinery, electronics, automobiles, light industry, building materials and national defense. Polishing is a significant process for mould manufacturing, thus plays an important role in ensuring the mould quality and improving its service life. 65% of the mould cavity is made up of curved surface, 40% of which is free-form surface. At present, polishing free-form surface mould is mainly manual with low production efficiency and unstable polishing quality.Focusing on the crux and hot topic of polishing free-form surface mould and combing the research supported by the National Natural Science Foundation of China (No.50575208), a novel robot-assisted gasbag polishing technique is proposed based on the gasbag polishing tool. This kind of technique is based on the on-line controllable flexibility, compliant contact, pose control and path planning, which guarantees the local surface shape amendment precision and the quality of free-form surface, and realizes the efficiency, accuracy and automation of polishing.Main work of this dissertation is shown as follows:1) Material mechanical performance and constitutive model of rubber is studied. Through the measurements of mechanical performance of rubber, the parameters of constitutive model are determined. The polishing contact force with different physical dimensions and shore hardness is researched and the gasbag is optimized. Based on the optimization outcome, the polishing contact force expression connected by downward depth and inflation pressure of rubber gasbag is established with experimental verification. Finite element analysis method and strain measuring technique are utilized to study the polishing contact force of gasbag polishing tool. Focusing on the link span of gasbag polishing tool, the max strain position is determined. The relational model between max strain position and polishing contact force is established. It provides a critical guarantee for the on-line control of polishing contact force with strain measurement. Experimental result indicates that measured result is agreed with theoretical mode.2) Mechanism of finishing, geometrical shape amendment and curved surface finishing is studied. Theoretical analysis is carried out for the shape, velocity, gasbag pressure and material removal rate. The pressure distribution discipline of contact area under large deflection of rubber gasbag is revealed and its model is established. Based on contact mechanics and theory of wear, the model of gasbag polishing material removal is established, which is a good theoretical foundation for the research of material removal mechanism and technological parameter optimization.3) Through polishing performance comparison experiment, the cotton fiber polishing cloth is adopted as the coated material of gasbag polishing tool. The configuration amendment and finishing effect influenced by each polishing parameter is analyzed. The sensitivity sorting and optimum combination of polishing process parameters are determined. A method of bi-objective optimization of process parameters and forecasting of processing results is proposed. The optimum combination is determined to ensure material removal rate and surface roughness and the forecasting results are obtained. Experiment verifies the accuracy of the prediction results.4) Based on the requirement of gasbag on-line adjustable flexibility and automatic polishing, the gasbag polishing tool is designed and the gasbag polishing experimental system is established, on which, the polishing on both flat and free-form surface moulds is realizied and a good polishing effect is obtained. A gasbag pressure pulsation polishing method which can improve the mould surface quality rapidly is proposed and the experiment validates the effectiveness of this method.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 free-form surface mould.