Large-scale titanium alloy fan blade profile CNC finishing
The blade surface finishing is to ensure that the profile roughness and waviness meet the design requirements and the material structure properties are not changed, and the geometrical dimensions and positional accuracy obtained by the milling process are basically not changed greatly during the machining. For actual machining, the blade profile finishing is based on the removal of the remaining machining marks and the required roughness and waviness. The amount of single-sided metal removal at each location on the profile shall not exceed 0.05 mm.
At present, the use of CNC abrasive belt grinding and polishing machine for blade surface finishing is a mature method for practical processing, and the use of CNC diamond grinding machine for blade surface finishing is an attempt One way. These processing methods are chosen because they have their own characteristics.
First of all, for the numerical control belt grinding and polishing machine processing method, it has the following characteristics: (1) abrasive belt grinding sharp grain, high grinding efficiency, has reached 10 times of milling, 5 times of ordinary grinding wheel grinding; (2) Abrasive belt grinding and workpiece friction are small, grinding heat is less, belt circumference is larger, abrasive grain heat dissipation time interval is long, easy to obtain complete cooling of air and cutting fluid, can effectively reduce workpiece deformation and avoid Burns and ablation; (3) the softness of the belt itself and the rubber body structure on the surface of the working wheel, ensuring that the belt is ground and in flexible contact with the workpiece, which has better running and polishing effects; (4) Belt grinding Stable abrasive size, because the abrasive belt is attached to the working wheel for grinding, the size of the abrasive has good stability; (5) The abrasive belt grinding can not be processed for a long time with large margin removal, and the abrasive belt contains The total amount of abrasive is limited, and the long-term processing of large amount of removal will cause the abrasive to be quickly consumed, and the processing needs to be interrupted for belt replacement.
The above characteristics of abrasive belt grinding make the mechanized production of large titanium alloy fan blade profile polishing under program control conditions a reality. At present, there are two methods for CNC grinding belt grinding methods for blade polishing: one is to use a six-axis CNC belt grinding and polishing machine, and the other is to use a robot numerical control belt polishing system. machining.
The motion function of the six-axis CNC belt grinding and polishing machine is similar to the five-axis CNC machining center during milling. The structural difference between the belt grinding wheel and the end milling cutter makes it necessary for the profile processing to adapt to the blade structure. It has a swing angle function in 2 directions.
The six-axis CNC belt grinding and polishing machine has the dual functions of profile grinding and polishing. The function change depends on the transformation of the power head in the form of rigid grinding and floating grinding. During the polishing process, the constant pressure floating mechanism is activated, which can precisely control the change of the grinding forward pressure through the pressure sensor, the grinding power sensor, the constant pressure cylinder and the like, and adapt to the difference of a certain range of the blade profile size. Polishing without destroying the accuracy of the profile. When performing the profile grinding process, the contact wheel floating mechanism is locked, and the rigid grinding of the profile can be performed. The rigid grinding of the profile can complement or replace the precision of the finishing of the profile. The size of the belt to be used should be changed according to the margin. This machining will change. The original dimensional position accuracy, and relative to the milling process, its excessive margin removal will produce large stress deformation. Therefore, the grinding function is not recommended on the premise that the milling has the ability to ensure accuracy.
The robot numerical control belt polishing method is performed by the robot holding the blade under the program control, and polishing on a fixed belt machine. The processing utilizes reverse engineering technology. Before processing, the robot takes the blade head part to scan the blade profile size, and then the data processing mechanism generates a machining control program, and finally realizes the blade polishing process under the program control. At present, the grinding method of the robot belt is limited by the motion precision, and is generally only used as a means of profile polishing.
The CNC diamond grinding wheel grinding method is a typical hard rigid grinding. The machine tool moving mechanism is basically the same as the five-axis linkage blade milling machining center, and the cutting tool used is to change the vertical milling cutter to the surface sprayed with the diamond powder. Cylindrical grinding wheel. Wide machining technology is used during grinding. This kind of processing method is hard and rigid grinding. Because the diamond grinding wheel itself has poor gas permeability, it can not achieve the heat dissipation effect by accommodating and exchanging the coolant medium, so it is not suitable for grinding the surface of the part with large margin, and even It is a process to remove a small amount of allowance. It is also prone to burns in the grinding of the blade profile of titanium alloy materials. Therefore, when using this method for the machining of titanium alloy blade profile, it is necessary to find a suitable cutting parameter, machine tool cooling. The way must be very effective. In addition, the diamond grinding wheel has a certain rigid edge grinding process for the hard surface grinding process. Although it can be improved by the matching adjustment of the program and the grinding wheel specifications, it can not achieve complete removal. The effect of blade fatigue performance is unfavorable. Therefore, supplementary measures must be taken to eliminate the complementary processing of the surface “ridge lineâ€. It may also be necessary to use the CNC belt grinding and polishing machine to perform supplementary processing under the corresponding program control. In addition, supplemental processing using a wet abrasive method with free abrasive properties should also be a viable method. Due to the above characteristics of the CNC diamond grinding wheel grinding method, its processing application is still in the exploration stage.
At present, the numerical control belt grinding and polishing machine method is becoming the most suitable method for large-blade surface polishing because of its many advantages. Its comprehensive advantage is that it can be used for dry grinding or wet grinding. It is also possible to perform ultra-low temperature grinding in the CO2 cooling mode, which is very advantageous for avoiding burns and ablation of the blade surface polishing of large titanium alloy materials. The application of CNC grinding and polishing machine tools has changed the labor intensity of manual polishing of large blade profiles, which plays an important role in improving the production efficiency of large blades.
Conclusion
The development and application of multi-axis linkage processing technology has greatly improved the precision and quality assurance capability of the large-scale engine fan blade profile processing. The processing efficiency has also achieved satisfactory results. Continuous research and improvement of equipment technology, large fan blade profile processing technology will develop towards mechanization and automation.
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