| Aero engine precision forged blade is one of the key components of aircraft engine. It is working in high temperature, high pressure and high speed, so the machining quality of the blade must meet accurate, precise dimensions and surface quality. Aero engine precision forged blade has many features, such as various kinds, great number, complex profile and machining difficulties and so on. The machining precision and machining quality of the blade for the whole aircraft engine performance and life have a vital role. At the same time, the section shape of aircraft engine blade has an important influence on aero engine runtime that generates the thrust and the flow of air. In order to meet the aviation engine requirements which are high performance, high security, high reliability and long life, their machining precision must meet strictly standard. If the machining accuracy of blade can’t meet the design requirement of theory, namely actually dimensional accuracy and cross section shape are serious distortion to lead that edge of blade and the surface can’t be smoothly connected. This blade will lead to engine asthma、idle instability and so on in the process of operation, and these problems are a serious threat to flight safety.The precision forging is usually manufacturing method of modern aircraft engine blade, the surface precision of blade is based on forging die and the surface doesn’t need the secondary processing. Because the edge curvature change of blade is serious, the distribution of machining allowance is uneven and unknown, it can’t adopt the rigid milling machining method. Flexible grinding is used to machine the blade edge. Firstly, the blade edge is measured to get machining allowance in order to calculate the real time grinding pressure. Secondly, the process parameters, such as abrasive belt type, linear velocity, feed speed and so on, are determined by the experiment. At last, the blade edge is machined by adaptive grinding.The main contents and research results are as follows:1 According to the machine processing and technical requirements of blade surface allowance-free of the aircraft engine precision forging blades, CNC abrasive belt grinding processing scheme is determined to apply in blade grinding. Based on the six axis linkage CNC abrasive belt grinding of the complex surface, this paper put forward to increase the axis to control the contact force which is between the work piece and tool, namely machine tool edge grinding method of seven axis linkage CNC abrasive belt grinding. At the same time, the control system of contact force which is between contact wheel of abrasive belt and blade is studied. Then the seven axis linkage CNC abrasive belt grinding process of aero engine precise forging blade edge is studied to determine the trajectory planning scheme, and optimize the abrasive belt, contact wheel, abrasive belt linear velocity and feeding speed of work piece parameters.2 The allowance model of precision forging blade edge is set up to calculate the allowance of blade edge over each cutter contact. According to the detecting data of the blade measurement machine, blade surface is rebuilded and it does the error analysis. The relationship between grinding parameters and the machining allowance is proposed and this paper designed orthogonal experiment to determine the relationship among the parameters.3 Based on the CAD three-dimensional model of the blade, through the analysis of the blade, geometrical information of blade surface is got. According to these data, this paper research the characteristics of abrasive belt grinding and six axis linkage theory of abrasive belt grinding complex curved surface to plan the cutter path, to pick up the cutter contact, to calculate vector of the support and axis of contact wheel. Eventually cutter location points will be got. According to the allowance distribution of blade edge, the data of the seventh shaft, which controls contact force between abrasive belt and blade, is calculated.4 This paper used Open CASCADE as geometric kernel, applied VS2010 for development platform, used C++ for programming language, and applied the differential geometry knowledge to develop adaptive processing software of aero engine precision forging blades. The system has many functions such as Reading the 3D model, setting coordinate system, selecting processing surface, producing tool path, generating processing locus and so on. Users will import blade three-dimensional model to software platform and enter the corresponding processing parameters, then the automatic programming of NC program can be realized on the system. It applied VERICUT as the simulation platform to verify NC code which is generated by the system. At last, the machining experiment is processed in order to verify the correctness of the software further. |
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