Research On The Digital Machining Simulation For Francis Hydro Turbine's Blade

Hydraulic turbine is a kind of power machinery in water power-generation, the manufacture quality and accuracy of the profile of the turbine runner's blade will directly affect safety, security, economic operation for power plant. Hydro turbine blade is a very complex body closed by sculptured surfaces, traditionally, for large-or-medium-sized blades, the manufacturing process of "casting - manual grinding—inspection and measuring with 3D template" is widely used. However, this process can't guarantee the accuracy of the blades effectively. In recent years, the technology of large-sized turbine blades with multi-axial NC machining tool has been researched by hydraulic turbine manufacturers. In NC machining process of the blades, a step called "trial machining" is still required for the verification and modification of the process procedure and NC programming. This is not only cost very high but also lower the productivity. Digital machining simulation technology is a powerful tool to solve these problems, which can simulate the process of machine moving and cutting on the computer.This thesis focuses on machining simulation of Francis hydro turbine's blades. A series of key technologies for simulation of the multi-axis NC programming manufacturing of Francis hydro turbine's blades are involved, which include establishing of 3-D model and orientation based on machining requirement, the multi-axis tool path planning and generating for blades, tool axis orientation for multi-axial NC machining of blades, establishing of environment for machining simulation, computer simulation for machining of a large blade to verify the gouges and collisions between machine tool andblade& fixtures;and post-processing in the programming. To simulate the digital machining of large-sized Francis hydro turbine's blades with multi-axial NC machine tool, by combining these research works with multi-axis NC programming of hydraulic turbine's blades, and re-development works have been done based on UG and other software.Digital machining simulation for multi-axis NC machining of large-size turbine blades is realized by mapping of the practical NC process in the virtual machining environment, which is used to verify the NC programming and processing before actual manufacturing. By computer simulation of machining we can check the correctness and rationality of NC programming, and avoid the collision between machine tool and blade or fixture. It is a technology basis for guaranteeing the safety of technics system and the quality of blades, evaluating and optimizing manufacturing plan. In this way, the period of blade manufacturing can be shortened, manufacturing cast can be decreased, and the quality of blades and machining efficiency can be improved. It is of great significance in improving the manufacture technology of hydraulic turbine in our country and making our hydraulic turbine manufacturer's technology up to International advanced technology level.