The aerospace industry has always been a key development industry in all countries in the world. In addition to strict quality system certification and highly complex integration technology, it also has the characteristics of high added value and high industry relevance, which makes all countries take the development of the aerospace industry as a national industry.
Five-axis Machining Technology is Developed in the Aerospace Component Manufacturing Process:
Free-form surface technology (sculptured surface) has been widely used in modern engineering design to replace lofting surface technology, such as automotive sheet metal molds, injection molding molds, turbine blades, ship propellers, and aerospace components. Based on performance considerations, these product features are complex three-dimensional surfaces. For example, processing with a traditional three-axis machine tool must not only overcome the original shortcomings of poor efficiency and accuracy but also consider the errors caused by repeated positioning and clamping. The cost of fixture design and manufacture. These limitations due to the freedom of the machine tool and the selection of tools can be overcome if the five-axis machining technology is used.
In theory, multi-axis machining has more advantages in manufacturing than traditional three-axis machining, including higher productivity and better machining quality. However, in practice, multi-axis machining also has many shortcomings, such as the complexity of the simultaneous movement of the tool in the multi-axis machine tool, the interference between the tool and the surface, and the collision. With the addition of two rotational degrees of freedom, multi-axis machine tools not only provide flexibility in machining but also create new problems that traditional CAD/CAM systems cannot adequately support. Algorithms for gouge and collision detection between the tool and adjacent surfaces are quite difficult. Due to the complex structure of the multi-axis machine tool, the dynamic accuracy of the machine tool needs to be more stringent. For the processing of multi-axis NC data, the controller design of the machine tool must be more complicated, so that the tool path can be processed by the interpolator to ensure machining accuracy.
The current commercial CAD/CAM software with multi-axis machining capabilities is still quite expensive, and when machining complex surfaces, it is quite inflexible in specifying tool orientation and tool path distribution, and generally requires multiple attempts to succeed. Traditionally, the orientation of the tool is usually kept constant during the machining process. During the tool movement, the orientation of the tool deviates from the surface normal vector by a certain angle, ranging from approx. Although this method is more efficient than the three-axis spherical milling cutter, the problem of overcut still exists, and the residual material left on the surface needs to be manually ground and removed. And these problems will be more serious when the surface is more complex.
- Cutting process planning:
Nowadays, the design of curved surfaces of products is becoming more and more complicated. The degree of freedom provided by multi-axis machine tools has the advantages of avoiding interference, reducing repeated positioning errors, and reducing the cost of fixtures. When processing curved surfaces, it can make the production process more convenient. Resilient and automated to meet the requirements of today's competitive environment for manufacturing. For the processing requirements of difficult-to-cut materials (titanium alloys, nickel-based superalloys), based on the complex surfaces and geometric features of precision components, the manufacturing procedures for positioning and multi-axis simultaneous machining are established. It is necessary to consider the cutting chatter and processing mode and plan and design the corresponding fixture and machine tool. With the aid of online cutting force analysis, plan tool paths for equal cutting forces. Taking the impeller as an example, trochoidal machining is used for roughing the blade surface. The advantage of this method is that the equal amount of cutting prolongs the tool life, and the roughing time can be reduced by a larger depth of cut. Impeller surface finishing mode, including point contact machining and side cutting technology, the selection criteria are the degree of surface torsion and surface tolerance. If the curvature of the surface changes smoothly, the side-edge cutting technology is far superior to point contact cutting based on the cutting efficiency.
- Five-axis machine tool post-processing program development technology:
Post-processing is an important interface between machining program design and manufacturing. Generally speaking, post-processing programs convert tool position data into data required for machining operations, such as program origin setting, machine origin setting, spindle speed, and tool feed. Tool coordinate control point, so CNC machining can be performed after the CNC machine tool accepts these data codes. Because machine tool controller manufacturers often fail to define control codes by international standards, post-processing conversion must define relevant control codes according to various types of controllers, and if the factory has multiple machine tools with different controllers, it must be prepared different post-processing to convert, so post-processing becomes more important.
Since the machine tool structure is a kinematics chain composed of various connecting rod joints, the joints are nothing more than sliding pairs or rotating pairs. Therefore, the kinematics kinematic chain relationship can effectively describe the motion trajectory of the machine tool in space, and the derived tool machine can provide the geometric motion range of the cutting tool, which determines the function of the machine tool. The derivation of the post-processing program is based on this concept to obtain the shape creation function matrix of the five-axis machine tool, and then use inverse kinematics to solve the parameter equations of each axis that control the machine tool. Therefore, the derivation of the joint limit and post-processing program of the multi-axis machine tool is based on the principles of forward kinematics and inverse kinematics. Use the homogeneous coordinate transformation matrix to describe the relative positional relationship between the axes of the multi-axis machine tool and the tool, and then make this matrix equal to the planned tool position matrix to solve the multi-axis machine tool. The motion parameter equations of each axis are required.
- Solid cutting verification and virtual error analysis:
To avoid interference between the five-axis toolpath and the surface, it must be verified through solid cutting simulation, and the simulation in general CAM software is based on reading the tool position file. It is impossible to know whether there is interference or collision. Whether the established five-axis toolpath can meet the machining tolerance requirements can only be accurately judged through NC program cutting simulation. Through the assistance of solid cutting simulation software, virtual manufacturing and error analysis are carried out. On the other hand, based on the tolerance requirements, it is necessary to verify whether the planned machining process, the chord difference, and the spacing set by the tool path generation meet the requirements. The tool path setting conditions can be further adjusted through the error comparison analysis.
Multi-axis Addition and Subtraction Composite Process Technology (CNC + 3D Printing):
Remanufacturing is also known as the ultimate form of replacement of failed components. The energy consumption, cost, and required materials of this process are only part of the new product. The remanufacturing of general mechanical components must rely on skilled technicians and a series of labor-intensive operations, often requiring a round trip between remanufacturers and outsourcers. However, this form of remanufacturing is quite difficult for high-value components that require strict quality control and production aging considerations. In the repair process, using high-speed metal cutting or grinding removal process, online scanning and inspection technology, and cladding/welding technology, there is an automated equipment foundation, but it has not yet been integrated into the stage of commercial availability. At present, the repair methods of general impellers still rely on manpower for many manufacturing processes. With the development of CNC equipment, the grinding, cladding, milling, grinding, and polishing before cladding are gradually replaced by machine tools.
- Arrange related processes and inspections in the same manufacturing unit and connect them in series through a robotic arm.
- Integrate these processes into a machine tool to form an intelligent and complex CNC machine tool (milling + inspection + laser cladding + inspection + laser heat treatment).
Based on cost-effective, fast, and reliable remanufacturing applications, a fully integrated production system and software have been developed to repair high-value components with minimal human intervention.
Re-manufacture of high-value products using a Combined Laser cladding, Inspection, and Machining system:
- High-speed scanning module
- Rapid laser cladding
- High-efficiency machining
- Adaptive CAD/CAM system
- System automation
- Workflow management
This system focuses on the repair of damaged components, the manufacture of new metal components, the updating of obsolete parts, and the updating of standard parts. Taking the repair of aerospace turbine blades as an example, including component alignment, defect identification, defect removal, defect repair, and finishing, the essence of this system is the maximum flexibility to face the most variables in the remanufacturing environment. For high-value components such as turbine blades and BLISK, the AM/cladding composite process technology can save time and cost in the process of manufacturing and repairing new products.
Rotary Ultrasonic-assisted Machining Technology:
Advanced materials such as brittle hard materials and composite materials have superior properties, so engineering applications are widely used in semiconductors, optoelectronics, aerospace, medical equipment, energy, electric vehicles, 3C electronics, precision machinery, and other fields. However, it is quite difficult to form or process such hard, tough, and high-temperature resistant advanced materials to the correct size and geometry, and the current technology and technology require high processing costs and time, which is limited in application. It is therefore important to develop a reliable and cost-effective process for these advanced materials. Compared with the current non-traditional machining process, Rotary ultrasonic machining (RUM) is relatively inexpensive, environmentally friendly, and suitable for the foundation requirements of traditional machining environments.
Rotary ultrasonic machining is a composite machining process (non-traditional machining process), which combines the material removal mechanism of diamond tools and the ultrasonic machining (USM) process. Under the dual motion of high-frequency vibration and high-speed rotation of the axial tool, forming a combined grinding and impact damage material processing technology. Can easily process high-hardness and brittle materials and can reduce the cutting stress generated when the tool/grinding rod contacts the material by 30-70%. As a result, tool life and surface quality are improved, and the material removal rate (MRR) is superior to diamond grinding and ultrasonic machining. In rotary ultrasonic-assisted cutting applications, including drilling, milling, and polishing processes, machining efficiency, tool wear life, and surface roughness are the main considerations. The technical application of micro-drilling mainly lies in polymer materials, composite materials, metals, and non-metals. When drilling ductile materials, burrs will be generated. However, when drilling brittle materials and composite materials, the edges of the materials will be cracked and damaged. It was confirmed that the use of ultrasonic vibration can improve burr generation in drilling. In the aspect of rotary ultrasonic-assisted milling, the surface processing of ceramics and sapphire brittle and hard materials focuses on the relationship between material removal rate and process parameters, including amplitude, static force, rotational speed, number of abrasive grains, and abrasive grain diameter. The polishing technology part mainly lies in the surface processing of sapphire brittle and hard materials.
Online Cutting Characteristic Analysis and Geometric Measurement Technology of Complex Surfaces:
Based on the needs of researching the cutting model of difficult-to-cut materials, cloud-based processing of big data, the intelligent operation of cooperative machine tools, tool life detection, and tool breakage prediction, the axial force during the cutting process is calculated through a tool holder with a sensor. , torque, a bending moment in X-Y direction and temperature, real-time measurement and output to the computer, as a basis for tool life assessment, tool design and development, process improvement, and productivity enhancement. The cutting characteristic information collected by the actual cutting test evaluation can be used as a reference for the selection of cutting tools and the basis for tool path planning.
In-process measurement refers to the work of measuring the production line. When the surface cutting is completed, the tool of the machine tool is replaced with a probe, and the measurement is performed directly on the machine tool. Online measurement can preliminarily inspect dimensions without loading and unloading workpieces. It combines the fields of design, manufacturing, and quality control, which can make the production process more flexible and automated. In the field of manufacturing integrated systems, the integration of numerical control machine tool cutting and online measurement and CAD/CAM system can achieve the goal of systematization and computerization of the process and enhance the image and competitiveness of the industry. Important considerations during online measurement include the setting of workpiece orientation, measurement procedures and path planning, collision assessment, error estimation, and error compensation and correction.
To reduce scrap, reduce machine downtime, increase productivity and flexibility in low-volume production, in pre-process machining settings, use machine tool probes to identify components to select the correct NC program, and locate datum features to create workpiece coordinate systems. Inspect Part size to confirm machining allowance and rough cutting program, and measure part orientation (relative to the machine axis) for coordinate rotation. In addition, using the tool setting instrument, you can measure the tool length to establish the tool length compensation value, check whether the tool length is within the set tolerance range, and measure the rotating tool diameter to establish the tool diameter compensation value. In the aspect of in-process monitoring, the tool probe software is used to plan the measurement path. The purpose is to confirm the reserved amount after mid-processing and the surface accuracy after finishing, and evaluate whether it is necessary to compensate the tool path to improve the machining accuracy. Improve process efficiency. To avoid errors in the measurement path program or interference with the curved surface, the measurement path simulation of the virtual machine tool must be verified before the actual machine measurement.
Prospects of Aerospace Parts Manufacturing Technology:
Whether in defense and aerospace, precision machinery, or even medical equipment, based on the consideration of energy efficiency, the design of product surfaces is becoming more and more complex, and advanced materials that are lightweight, harder, and more resistant to high temperatures will be widely used in the future, and traditional processing methods are no longer available. It is in line with the current production type of high output value, high precision, diversification, and low labor demand. The combination of the five-axis processing machine and the compound processing machine will maximize the processing range and type of a single machine. Because the five-axis composite CNC machining technology is of great help to the manufacture of high-value precision parts such as aerospace parts in terms of product accuracy and cost-effectiveness. Therefore, five-axis machine tools, multi-axis turning, milling composite machining, ultrasonic assisted cutting 、Five-axis addition and subtraction composite process technology are the focus of the development of composite machine tools. It combines various and multi-axis machining processes, which can not only reduce the process replacement time and fixture material expenditure but also provide advanced material processing technology and improve production efficiency. It is a high-efficiency and high-quality development model that reduces labor management costs.
Through the integration of CAD/CAM systems, virtual and real integration technology, composite process technology, and intelligent automatic process control technology, the process technology development of difficult-to-cut materials for aerospace parts can not only ensure product accuracy and delivery time but also collect and analyze various production processes. The real-time production information of the equipment and the online cutting load provides the optimum manufacturing conditions and discover the root cause of the abnormality so that the manufacturing will be more efficient and competitive.
