Development Of Polishing Machine Tool For Double-side Blade Finishing

Steam turbine, gas turbine and aircraft engine are widely used in energy transportation and defense field, the blade is one of the key components of these energy sources and power device. Blades work under the high temperature and high pressure conditions in a long period, and withstand the alternating stress of centrifugal force, water or steam.Blades are made of high hardness and high strength material to ensure the reliability and working life, which can result in the difficulty of processing.At present, the main trend of machining blade surface is using multi-axis CNC.Marks are left on blade surfaces after milling.Grinding and polishing process is needed in order to ensure the quality of blade surface.The blade finishing process is still mainly completed by manual polishing. The manual polishing has to be done at very poor working conditions and the finishing efficiency and accuracy are also very low, thus the health of the workers is seriously affected. polishing time take about 40%～50% of the total processing time. The polishing results often changes with workers's proficiency, the workers must have high skills. High techniques and skills need works practice frequently, and high techniques and skills are accumulated in a long time.The shortage of skilled workers becomes a problem because of the scale of production continues to expand. Therefor, this thesis develops a polishing machine tool for double-side blade finishing.First, according to the process of single particle and the force model, theory material removal model of single particle is derived, then theory material removal model of belt grinding is educed.This thesis proposes the method of control contact forces in belt grinding process as well.Sequentially, the polishing machine tool for double-side blade finishing is comprised of six parts based on the idea of modularization, platform base,X table,Y table,Z table,clamp system,precision electric rotational table,self-adaptability of the curve surface tool. Elementary design and thought of the machine are presented through analyse of the configuration character of the blade, elementary design to the polishing machine is also obtained with CATIA software. The ball screws which are drived by AC servo-motors move along the straight rail in X,Y,Z orientation.In order to adapt well with the curvature variations of the blade surface in the finishing process, a completely new tool system that has the self-adaptability of the curve surface was proposed in this thesis. In this tool system, a rotatable contact wheel holder is designed to realize the exchange of contact wheels according to the surface curvature variations.After that, static finite element analysis and modal analysis of equipment and the weaker parts are accomplished in this thesis based on the cell types in finite element analysis, the characteristics of grid, elements of the details and characteristics of the structure.Equipment deformation meets the requirements.Tool plate is made of aluminum to reduce the overall weight of the polishing tool. Equipment, columns and tool plate are calculated, the results show that the AC servo-motor does not resonate with the equipment.The paper also gives the description of the contact wheel selection.Finally, this thesis presents geometric trait of blade's section,then get machining path by equation of blade's section based on structural characteristics.According to motion simulation of the device, path, moment of columns, force of contact wheel and force of blade in a situation under constant feed force and positive pressure are described.