Design Of Virtual Prototype And Research On Key Technologies Of NC Shoe Last Machine

Based on the project funded by Zhejiang Province Technology Foundation in 2002—Development of Shoe Last CAD/CAM System and the research on NC Shoe-last Maching, the key technology of virtual prototype in advanced manufacturing technology,the idea of knowledge-based engineering(KBE), knowledge fusion(KF), CAD&CAE intergration and muti-objective optimization are researched and applied to design shoe last machine. The rapid design was achieved.It has found a practical approach to shorten product life cycle and preserve design experience and knowledge.The main research tasks of the article are as following:1. The concept of the knowledge-based engineering (KBE) was annotated, as well as the advancing process of the KBE System was discussed.Based on the Full analysis of the structure,function and performance of the shoe last,The design programme of the NC Shoe-last was constructed The FBS(Function-Behavior-State)mapping model in concept design is presented. The processes of computer aided conceptual design based KBE is studied and the structure design programme is realized.2. The prototype of NC shoe-last machine is designed by the virtual prototype technology.By the using the KBE,the knowledge fusion technology(KF) is applied in the modelling process of shoe last machine.Knoeledge,rule and experience are integrated.The bidirectional control model based on IMM(Integrated Master Model)was got. It also deeply researched The knowledge driven representation in KF was in-depth studied and repplied.The whole digital model was builded at last.3. In order to improve the precision of shoe last machining, a surface model construction method for shoe last was put forward. With reverse engineering method, the points data of shoe last was acquired by laser scanner. Based on wavelet transformation, Stein's unbiased risk estimate was used to smooth and de-noise measurement data. Three-order non-uniform rational B-spine(NURBS)surface was adopted to fit the shoe last surface. Interference-free tool path was generated by the constant scallop height principle. The Mathematical Model of shoe last was set up on Unigraphics software to simulate the numerical control machining process of shoe last. The results showed that the accuracy of shoe last surface could be adjusted with this reconstruction method. The tool path could be conveniently computed according to the acquirement of machining efficiency and the errors compared with the given machining precision were acceptable within permissible limits.4. The project of CAD&CAE process integration was in-depth studied by use of SPS (Simulation Process Studio) technology.It successfully applied in the dynamic characteristics analysis in parts of shoe last machine.It is a new convenient way in the product development and optimization design. The gantry column was optimized by MOGA-II(Muti-Objective Genetic Algorithms) arithmetic based on pareto optimality and DOE(Design Of Expeiments) technology in order to reduce weight and guarantee dynamic characteristics5. Through studying the NC system the measures resisting interferences by means both of hardware and software were presented. The hardware measures included electrical source, signal-line and grounding-system et al. The software measures included software trap, software filter and software fault-tolerance et al.. With this technology, the NC system of shoe last NC machine runs steadily and reliably. A neural network PID control method used to reduce contour error based on genetic algorithm optimization is presented by analyzing the relation between the contour error of servo system and the system dynamic performance. The proposed control strategy was proved effective and the contour error was controled in an acceptable rangle.The advanced manufacturing technology was applied to design,research and development of shoe last NC machine.The technology and process have an important reference value in other similar mechanical structure design.