Composite machining technology of high-speed grind

New generation aero-engine rotor tip high-speed grinding composite machining technology

author unit: Shenyang Liming aero-engine manufacturing company

facing the rapid development of the aviation industry, the new generation aero-engine rotor assembly structure has been completely different from the first and second generation engines, which also puts forward higher requirements for rotor blade tip grinding. In recent years, with the mass production of three generations of engines, the overall manufacturing technology level has been greatly improved, but compared with the international advanced aero engine mechanism, the resolution is 1/200000, and the displacement accuracy is ± 1% Compared with manufacturing enterprises, there is still a big gap in individual manufacturing processes, including high-speed blade tip grinding process. At present, the use of high-speed tip grinding for rough and fine machining, detection and deburring of various types of engine rotor blade tips has been a widely used process technology in foreign aero-engine manufacturing companies and maintenance companies. The circumferential assembly structure of the rotor blade and drum of a high-pressure compressor rotor of an engine is different from the axial dovetail mode of any model. The fit clearance between the blade and the tongue and groove is larger, which is more than 5 times higher than that of other models. Under the condition of large blade activity requirements, grinding the outer diameter of the blade to ensure its tolerance and radial runout requirements has always been the goal pursued. See Figure 1 for the rotor structure and technical requirements. For many years, in order to grind its blades under tension, it often requires the joint efforts of automobile manufacturers, parts enterprises and raw material manufacturers to adopt the process method of installing each blade on the simulation disk, jacking up the blades one by one with screws, and using ordinary reformed equipment to grind all levels of simulation disks at low speed. Not only the production efficiency is low, but also the quality state is unstable, which cannot meet the design requirements. Adopting high-speed grinding and new measurement technology is the most effective way to improve the machining efficiency and quality level of rotor blade outer diameter grinding. The high-speed blade tip grinding process enables the rotor blades to obtain enough centrifugal force under high-speed conditions through high-speed workpiece rotation speed. The blades with large activity are ground and measured in the state of being close to the tenon groove of the drum. The outer diameter dimension after grinding is consistent with the working state. It is an important process means to ensure the engine performance and ensure the engine oil consumption rate of the compressor rotor under the minimum working clearance

engineering application characteristics of high-speed blade tip grinding equipment

the model of high-speed blade tip CNC grinding machine is dantip R3 1500/2000, and the maximum speed of grinding workpiece can reach 4000r/min, which meets the technical requirements of machining blade tip size when all stages of compressor rotor blades are in outward tension. Ge/fanuc series 16i CNC control system is adopted, and its measurement system is dan-btm725 non-contact measurement system, which is used to measure the outer diameter dimension of blades at all levels, and display the outer diameter dimension of each blade at all levels measured each time in the form of data and graphics. The provided LVDT probe measurement system is used to measure the non blade surface of the rotor. The high-speed tip grinder has the function of automatic dressing of grinding wheel, and can set the automatic dressing time of grinding wheel by program. The dust suction device and standard air conditioning system provided by the high-speed blade tip grinder are respectively used to absorb the debris generated during grinding and control the temperature in the protective cover to ensure accurate measurement results. The high-speed blade tip grinding equipment is a compound processing machine tool (see Figure 2), and its main performance parameters are shown in Table 1

application scheme of rotor high-speed tip grinding process design

high-speed tip grinding process design has three meanings: first, the efficient machining technology of high-speed grinding of rotor blades in tension; Second, the composite processing technology based on the principle of process concentration will enrich the technology; The third is to realize the measurement technology of detection

1 efficient machining technology of high-speed blade tip grinding

NC High-speed blade tip grinding technology has completely overturned the process of grinding blade outer diameter with the original ordinary turning grinder. Its technology is mainly realized through reasonable process design, correct clamping method and efficient grinding parameters

(1) click "report editing" process design

NC High-speed blade tip grinding has high requirements for the self imbalance of the grinding workpiece. If it exceeds the set value, the alarm will be given to interrupt the grinding. Therefore, a series of balancing processes need to be adopted to pre balance the rotor before high-speed grinding. After tests, the final imbalance of the rotor pre balanced is controlled within 25g · cm. 1. The outer diameter allowance of stage 2 blade is large, and a rough grinding process is arranged. Its process flow is shown in Figure 3

(2) clamping method

in order to ensure that the relative reference runout of the blade tips of stage 1 ~ 9 blades after grinding is within 0.05mm, the hydraulic tooling with interference fit between the rotor reference and the tooling reference is adopted. By controlling the radial runout of the front and rear hydraulic chuck tooling with which the rotor is matched not to be greater than 0.01, the rotor is closely matched with the fixture through the air tightness inspection under the pressure of 0.2MPa, so as to achieve the accurate positioning that the rotor design reference is closely matched with the machine tool processing reference. After many tests and machining verification, the 48 nuts at the grate disk and the base were checked to ensure that the rotor could be grinded safely

(3) grinding parameters

there are three key points to set the grinding parameters: first, the selected speed can ensure the grinding of the grinding blade in the tensile state (that is, the blade is in the working position); Second, because the material of rotor blade is titanium alloy, the grinding parameters selected should ensure that the blade is not burned after high-speed grinding; Third, the stability of high-speed grinding process. The three key points restrict each other and need to be tested together

through a large number of experimental studies, it is verified that the rotor speed, the size of the blade outer diameter size allowance, the blade angle and the burrs produced in the grinding process have an impact on the grinding stability and the burning of titanium alloy blades. In order to minimize these effects, the rotating speed is set in stages, different feed rates and residence times are set in different grinding stages, different parameters are set in different stages, and 0.2 ~ 0.3mm allowance is reserved for rough grinding After deburring, carry out fine grinding of blade outer diameter and other methods. The determined high-speed grinding process parameters are shown in Table 2

2 composite machining technology based on process concentration

improving production efficiency is an eternal theme in the part cutting process. High speed blade tip grinding completes various machining and measurement requirements of blade outer diameter grinding, sharp edge deburring and measured outer diameter under the same equipment and the same benchmark, and realizes multi process composite machining with one clamping, which greatly shortens the rotor machining production cycle, Improve the machining quality of rotor blade outer diameter

for stage 1 ~ 9 rotor blades, the method of step-by-step grinding and step-by-step deburring is adopted. Through exploration and a large number of tests, the high-speed grinding speed and deburring speed are determined (see Table 2), and the roughness is 0.8 μ M

3 detection technology

the detection of the grinding of the outer diameter of the engine rotor blade is controlled by the preparation of the grinding program. The rotor blade of level 1 ~ 9 is ground step by step to achieve the size and angle specified in the drawing. The measurement is carried out by the method of real-time tracking, monitoring and measuring the outer diameter of the grinding blade with a non-contact measurement system, and the measurement accuracy is 0.001mm. The blade outer diameter angle is guaranteed by the appropriate radial distance compensation after the grinding wheel head frame rotates the corresponding angle. This measurement can eliminate the repeated positioning error to the greatest extent, and the machining accuracy is easier to be guaranteed

application evaluation of high-speed tip grinding and measurement technology

in order to verify the correctness of the application results of high-speed tip grinding technology, the simulation disk and three coordinate measurement are used to compare the blades at all levels of high-speed grinding. The test results show that the diameter difference of each blade measured after high-speed grinding is 0.007mm, and the diameter difference of each blade measured on the simulation disk is 0.024mm, The outer diameter difference of each blade measured by three coordinates is 0.0074mm. Through the comparative analysis of the test data of other levels of blades, the outer diameter of the blades grinded by the high-speed tip grinder measured on the simulation panel and the three coordinates meet the requirements of the dimensional tolerance zone given by the design, and the accuracy of the measured data on the high-speed tip grinder is higher than that on the simulation panel and the three coordinates. The accuracy of grinding blade outer diameter by high-speed tip grinder fully affirms its machining accuracy and measurement accuracy

conclusion

the high-speed grinding, deburring and measurement of the outer diameter of the rotor blade are used to solve the grinding of the outer diameter of the rotor blade of the new generation engine, which overcomes the difficulty that the rotor blade needs to be ground under the tensile state of the working position proposed by the design for many years. At the same time, it effectively overcomes the problems of repeatedly assembling the blade, grinding the blade and deburring time-consuming, and the measurement error of the blade tip size, And this composite processing technology greatly reduces the number of work positioning, shortens the processing process, and improves the production efficiency and product quality. This shows that the compound processing technology based on process concentration is an important means to improve the manufacturing level of the new generation of engines, and it is also the development trend of international advanced manufacturing technology. This complex and efficient processing method can be applied in the military and civil aircraft enterprises of AVIC, but it needs to be comprehensively considered from the aspects of workpiece structure design and processing economy. (end)