Study On Novel Gantry Hybrid Grinding And Polishing Machine Tool For Blade Finishing

With the development and application of the engine with impeller, such as steam turbines, turbines and aircrafts, the blade is one of the important parts and its quality directly affects the performance. It is complicated to design the blade because of the high precision and the composition of spatial complex surfaces. By the way the blade always works in poor conditions. So, it is required greatly of the design, materials, machining and the processing of thermal treatment. The drawbacks in the design and manufacture affect the efficiency, and even make the whole machine damaged. Because of the widespread application of commercial CAD software, the design of blades is greatly promoted. But in the processing of manufacture, the blade grinding and polishing needs many workers to meet the requirements of surface precision. It is often difficult to guarantee the quality of the surface and costs much time.A novel gantry hybrid grinding and polishing machine tool is researched and manufactured to improve the automation of surface grinding and polishing and the efficiency of exploitation, shorten the period and decrease the effects of human. This equipment combines with the advantages of parallel mechanism and traditional machine tool. It can not only take advantage of high stiffness, high accuracy, high flexibility, but also with two transfers DOF greatly increase the workspace. This machine tool easily solves the problem of small workspace of parallel mechanism, and is adapted to the blade machining. The platform of parallel mechanism has three DOF, which are the linear motion along Z-axis, the rotated motions around X-axis and Y-axis. The four DOF cross section of blade can be formed by the coordinated motion of the tool along X-axis and three DOF of 3-RPS parallel mechanism. Plus the linear motion of Y-axis, the whole surface of the blade can be machining. This machine is the first time to be proposed by our laboratory. Two patents are authorized. One is invention patent (patent number CN101148021), and the other is utility model patent (patent number CN201109062).This article is supported by the key project of Jilin province science and technology development plan. The research on the novel gantry hybrid grinding and polishing machine tool is consisted of the needed freedoms of the machine tool, the distributions of freedoms, the configuration of transmission chain, and the design of core components and the whole structure of machine tool. The machine tool has been assembled, and is being debuggedThe absolute DOF of the 3-RPS parallel mechanism are established, and the kinematics and dynamic analysis are completed. The models of location, velocity and acceleration are established which are between the absolute DOF and drive. The model of dynamic is established by Lagrange. Considering the structure design and the kinematic analysis of the 3-RPS parallel mechanism, the work space is solved with different locations and poses.According to the spiral gotten by blade reconstruction, the motion planning and trajectory planning is finished. Needed motions are assigned to the active DOF of machine. Then, the machine motion simulation is finished. In the process of simulation, there are great impacts when the edges of blade are being grinding. Interpolation is used at the edges of blade to increase the data points, narrow the distance between two points. There are no obvious impacts in the whole process of simulation by means of interpolation.The finite element model of 3-RPS parallel mechanism and the whole machine tool are established by means of simplifying the part and joint. The static and dynamic properties of machine tool are analyzed. The stiffness of machine tool is great, and the maximum stress and the maximum strain happen at the tool. The same frequencies of machine tool are gotten by means of finite element and experiments.The precision testing experiments of the X, Y axis motions and the single factor experiments of blade grinding and polishing are finished. In the process of precision testing experiments, positioning precisions, repositioning precisions and straightnesses of X, Y axis are tested. In the process of single factor experiments of blade grinding and polishing, the belt particle sizes, belt speeds and feeding speeds are changed. The experimental results show that the belt particle size can affect the blade processing quality. The greater of belt particle size, the higher belt speed and the higher feeding speed make the quality better.