Abstract Advanced materials and manufacturing technologies are important material and technical foundations for the development and production of aerospace engines. Engine quality continues to decrease, and engine efficiency, service life, stability and reliability continue to increase. Aeroengine materials and manufacturing technology are toward high temperature, composite, lightweight...
Advanced materials and manufacturing technologies are important material and technical foundations for the development and production of aerospace engines. Engine quality continues to decrease, and engine efficiency, service life, stability and reliability continue to increase. Aeroengine materials and manufacturing technologies are evolving toward high temperature, composite, lightweight, integrated, high efficiency and low cost. The new overall structure of aero-engines, high-reliability lightweight construction, and the rapid development and application of precision, high-efficiency and low-cost manufacturing technologies have made engine components lighter and lighter. The effective improvement of manufacturing techniques such as casings, blades, disc shafts and integral leaf discs is inseparable from the development of machine tool technology. Typical part processing technology
Aeroengines use a large number of difficult-to-machine materials and composite materials such as titanium alloys and heat-resistant alloys, which play an important role in promoting and promoting the development of machine tools. At the same time, the continuous development of surface integrity machining and intelligent control technology, complex thin-walled parts multi-process composite processing technology, engine parts efficient green processing technology, etc., puts higher requirements on machine tools, not only to solve structural deformation and Precision control issues, and full study of surface integrity control issues.
Machine tool processing technology
(1) Deformation control of machine parts. The machine is a weak rigid part, and the design precision of the mating surface is high; the materials are mostly difficult-to-machine materials such as high-temperature alloy and titanium alloy; the machining allowance is large and the distribution is not uniform. It is easy to deform after processing, combined with these characteristics of the casing, the following measures can be taken to reduce the deformation of the machine parts after processing: 1 Reasonably arrange the processing route. 2 Choose the correct positioning and clamping method. 3 Develop fixtures that enhance the rigidity of the cutting system. 4 Reasonably plan the cutting path. 5 Control the amount of deformation after roughing. 6 Clear the detection status of the machine.
(2) Machine programming template technology. Due to the complex structure of the casing parts and the relatively concentrated processing content, the design of the CNC machining process is extremely complicated. Most parts are arranged in hundreds of processing steps in one process, and dozens of tools are required. The programming specification cannot elaborate on some contents.
The programming process can be simplified by processing the curing method in the template, the cutting method, the machining allowance, the machining tool, the advance and retract mode, the machine control and the feed amount. It eliminates the tedious setup of machining tools, machining method groups, and various machining parameters. The optimized workflow facilitates the programming of the part processing program, reducing the fatigue strength and programming error rate of the programmer. UG template file creation steps: 1 Define the processing template type. 2 Create a machining method group and a tool group. 3 Determine the processing parameters in the processing template. 4 Create a tool magazine. 5 Set template association and inheritance relationship.
As the level of CNC machining technology continues to improve, the template files need to be updated accordingly to timely absorb the latest processing technology to meet the needs of on-site lean production.
(3) Unattended CNC machining technology refers to the processing of processed products in the digital control processing equipment, with no intervention or minimal human intervention, and the processing quality and quality stability of the processed products are not affected by human factors. process. Finally, the machine door is closed → press the button to start the machining program → the program execution ends → open the machine door → remove the qualified parts, without manual measurement, tool change and adjustment procedure.
In principle, the NC machining program of the machine parts should have the following characteristics:
1 Timeliness: On the basis of ensuring the quality and safety of parts processing, efficient processing in the whole process is realized.
2 Precision: The non-intervention NC program must ensure the main dimensions and fit dimensions of the part processing, the quality is controllable, and the difference is close to the size.
3 High automatic: By adopting automatic tool change of machine tool, automatic tool setting and on-line measurement technology in the machine, the whole process NC machining has no intervention or less intervention, and the machining process is carried out at 100% magnification. The operator does not need to adjust the feedrate override. 4 Error-proofing: The logic judgment command is used to monitor and manage the input values ​​in the whole process of processing. When an error occurs, the corresponding protection measures are automatically taken. 5Interactivity: Make full use of the machine tool function, display the tool change information and error prompt information in the process in the processing process in time and accurately on the operation panel to remind the operator to perform corresponding operations.
2. Overall disc shaft efficient turning and milling combined machining
The integral disc shaft part is a typical disc shaft integral structural part. It is an important bearing part of the new structure integrating the compressor disc and the journal. It has the characteristics of complex structure, high dimensional accuracy, poor rigidity and difficult material processing.
In particular, the semi-closed deep cavity structure is formed between the journal cone wall and the disk floating plate, which has poor openability and high processing difficulty. The processing of such parts is required in the traditional machining process in the numerical control lathe, the coordinate boring machine, the five-coordinate Completed on a variety of equipment such as machining centers. The processing cycle is long and the processing quality is unstable. The overall disc shaft adopts turning and milling CNC machining, and the ACE (Automatic Control Equipment) program, constant linear speed cutting, on-line measurement and automatic compensation CNC machining technology are used to effectively integrate machining, measurement and compensation into the same block. The machine tool is the continuous machining mode of the process execution body, reducing the probability of human error and unnecessary downtime. The innovation is that the process is highly integrated. Once set, complete the car, milling, drilling, expansion, boring, hinge processing, one time forming. Greatly improve the processing quality and processing efficiency of parts.
By designing the whole process unmanned CNC machining program, the problem of large dimensional tolerance and quality instability of parts in traditional machining is improved. In the deep cavity machining of the whole disc shaft parts, the high-pressure internal cooling structure tool and the ultra-high pressure target chip breaking technology are used to develop and apply the B-axis oscillating turning technology, constant linear speed cutting, online measurement and automatic tool wear compensation. The machining method of axial layered cutting and radial layering cutting effectively solves the technical problems of cutting chip, tooling and vibration of the whole disk shaft parts by optimizing the cutting parameters, cutting method and path.
3. Processing of the whole leaf disc
The whole leaf disc is made of a whole body of the blade and the hub, which has the advantages of light weight, avoiding the loss of the airflow of the steamed head, and the like, and is widely used in the advanced aeroengine. The overall leaf disc structure is complex, the blade profile is a complex free-form surface, the distortion is large, the processing precision is high, the passage between adjacent blades is deep and narrow, and the openness is poor, which makes the overall blade disk difficult to manufacture, and the processing between the blades during processing. The area is narrow, the tool can be moved in a small range, and the processing area is constrained to be harsh, so that the direction of the tool vector changes sharply during the machining process.
High-efficiency processing of the whole leaf disc is a high-performance processing technology that improves the processing efficiency and equipment utilization and reduces the production cost by optimizing the machining process and improving the material removal amount per unit time under the premise of ensuring the accuracy and quality of the parts. It covers high-efficiency machining technology, high-efficiency machining CNC programming technology, efficient machining tool selection and application technology, and intelligent control of machining process. By selecting advanced cutting methods such as small depth of cut and large feed, the process stress concentration is reduced, the non-uniform and unsteady residual stress on the machined surface is reduced, and the fatigue strength of the part is improved.
4. Blade profile CNC milling
The blade adopts a five-axis machining center, and the advantages of integrated CNC machining realize the numerical control machining of the blade body profile, the arc-shaped hoe, the dovetail-shaped hoe, the groove on the blade body, the journal arc groove and the blade shoulder arc. Compared with the traditional processing method, the process is shortened by 40%, and the manufacturing capacity of the tool is reduced by 70%.
Blade CNC milling cutters usually have rounded end mills, ball end mills, and tapered ball end mills. In general, these standard tools should be selected for blade milling. When conditions permit, the machine clamp tool should also be selected to reduce the tool cost of the blade.
When special parts and specifications are required for certain parts of the blade, some non-standard tools must be customized.
Due to the different blade configurations, even the same material has the same cutting allowance and surface quality requirements, and different cutting parameters may be required.
The blade profile has no margin for CNC milling, ie the blade profile after CNC milling should be within tolerance, including profile profile and position. To realize the CNC milling without margin, it is not enough to rely on high-precision numerical control equipment. It is also necessary to solve the stability of the blade wool state, the reliability of the blade CNC machining system, the regularity analysis of the tool state change and the mechanical polishing after the blade milling. A series of questions. Bladeless CNC milling is a systematic engineering technique that requires solving every problem in the entire process and maintaining the stability of the entire process system.
Application of machine tools in aerospace manufacturing
The aero-engine is a complex thermal machine that works reliably for a long time under the harsh environment of high temperature, high pressure and high speed rotation. It is a highly knowledge-intensive and highly intensive product. Aviation manufacturing is one of the main service targets of machine tool manufacturers.
1. Aeroengine manufacturing needs for machine tools
The increasing demand for precision and efficiency of parts processing in the aviation industry continues to drive the development of machine tool technology and is the source of innovation for machine tool products. The emergence of high-speed high-precision machining centers, composite machining and multi-axis linkage CNC machine tools are closely related to customer needs.
The development direction of machine tools: 1 High degree of automation, that is, the equipment is required to have digital and cutting-edge features, powerful software and high degree of automation. 2 Highly integrated, with few additional equipment and highly integrated equipment, enabling process compounding. 3 flexible, high degree of equipment, and strong applicability. 4 High precision, high efficiency, and intelligent, the equipment needs to have high precision and high technical maturity. 5 high stability, long precision retention time and low failure rate.
3 to 5 axis machining center, CNC lathe machining center, various grinding equipment, various precision forging equipment, various casting equipment, special electric processing equipment, composite machining center (turning and milling, milling), blade machining center and grinding Cutting centers, special electrical processing equipment, laser processing and strengthening equipment and surface treatment equipment are essential equipment for aerospace manufacturing.
(1) Basic requirements for processing equipment for disc parts. CNC vertical car: It should be compatible with the machined parts in terms of table diameter, positioning accuracy, repeat positioning accuracy, table speed and table weight. With automatic tool change function, the magazine capacity is large enough; the control system has the tool track graphic display function; it has USB port, DNC network receiving data port; it is equipped with high pressure internal cooling, onboard automatic tool setting function, onboard workpiece measurement function, Automatic temperature compensation; the machine has sufficient rigidity and reliability.
(2) Basic requirements for machine processing equipment. Worktable inverted five-axis milling machining center: with frame TRANS, AROT, tool nose tracking TRAORI, advanced measurement cycle, counting cycle FOR and subroutine call function; with USB port, DNC network receiving data port. Other functions: The machine is equipped with powerful internal cooling, on-board automatic tool setting function, on-board workpiece measurement function, temperature automatic compensation function, with breakpoint tracking function; the machine tool has sufficient rigidity and reliability.
(3) Basic requirements for blade processing equipment. Five-coordinate blade milling machining center: high linear axis acceleration, fast response; with adaptive machining function; blade processing software; on-machine detection, dual drive axis function; 24 or more tool magazines and machine tool setting device; Sufficient rigidity and reliability.
2. High-performance tool cutting technology application
As one of the main parts of cutting, the tool plays a vital role in solving the machining problems of aviation materials. Advanced aerospace products require aerospace parts with superior performance, lower cost and greater environmental friendliness.
The machining process requires faster processing speeds, higher reliability, high repeatability and reproducibility. High-quality, precise and safe cutting tools for difficult-to-cut workpiece materials such as titanium alloys and high-temperature alloy parts, complex and thin-walled shapes, high-precision dimensions and surface roughness requirements, and large metal removal. Wait for higher requirements.
The traditional tool can no longer meet the requirements of modern advanced and efficient machining, and the tool industry has entered a new pattern of modern tool production with high precision, high efficiency, high reliability and specialization.
Efficient indexable tools and superhard tools are the key to today's high-performance machining technology. The expensive price of imported tools restricts the promotion of advanced tools in China, seriously affecting the level and production efficiency of China's machinery manufacturing industry, and advanced tool structure. Research and development of high-performance tool materials, high-efficiency indexable tool series and super-hard tools are imperative.
When a new product is introduced to the market, it will effectively reduce the cost of machining. On the other hand, by developing high-efficiency indexable tools and super-hard tools, mastering the design and production technology of a number of high-end indexable tools with independent intellectual property rights can effectively improve the core competitiveness of China's machine tool enterprises in the international arena. The overall development level of China's cutting tool industry, to achieve sustainable development of cutting tools.
Tool companies should establish a CNC tooling process database for aerospace engine users.
Construct a serialized process design platform for CNC tools and develop new corporate standards for products. Focus on the protection of intellectual property rights, and realize the integration of high-efficiency cemented carbide tool production process technology for aviation engines.
3. Advantages and gaps of domestic machine tool tools
Although China's machine tool industry has made great progress in recent years, the numerical control rate has steadily increased, but the structural contradiction between machine tool consumption and production is still outstanding. Mainly reflected in the domestic demand for medium and high-end machine tools continues to increase, but domestic high-end CNC machine tools can not fully meet the demand.
4. Advice on the development of machine tools for aerospace manufacturing
(1) Raise the foundation with a point and a face.
Special research should not only take into account the mainframe and final products, but also consolidate the basic design and manufacturing theory of machine tools. Research on basic common technologies to improve the core competitiveness of machine tools.
(2) Focusing on key points and breaking through the key.
There are many types of equipment in the aero-engine industry, which can be concentrated on typical parts and machine tools. For example, cutting and grinding technology can be concentrated on the casing, blades, and integral blade/impeller. These three types of parts can concentrate more than 80%. The key technology. Concentrated difficult materials, complex surfaces and weak rigid structures. Once the relevant cutting and grinding technology is broken, other parts can be used.
(3) Do a good job after sales to achieve a win-win situation.
Machine tool enterprises should actively carry out after-sales service and implement “turnkey†projects. Understand customer needs, listen to customer feedback, master the world's advanced design concepts, design and manufacture quality products, and win-win with customers.
Conclusion
A generation of materials, a generation of manufacturing technology, a generation of process equipment, to create a generation of aviation products.
With the continuous development of aerospace manufacturing technology, the dependence on aerospace manufacturing equipment is becoming more and more high, which requires a high degree of integration of process research and equipment. The level of development of machine tools directly affects the application of manufacturing technology and the quality and efficiency of aerospace products. Seizing the opportunity and taking advantage of the situation, independent innovation is our important choice.
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