NC Machining Method of Aircraft Model

Wed Oct 12 10:26:54 CST 2022

The numerical control machining method of the aircraft model is specifically implemented according to the following steps: Step 1. The aircraft model is divided according to structural characteristics; the aircraft model is divided into wings 1, fuselage 2, vertical tail 3, horizontal tail 4, missiles and pylons 5, There are 6 parts of the pitot tube, among which the missile, the pylon 5, and the pitot tube 6 belong to the external equipment, which can be considered to be isolated from the model and processed separately. It is the part 1 of the wing that hangs out of the fuselage the most, and the flutter phenomenon is very likely to occur during the CNC machining process; secondly, the structural features of the aircraft model belong to the splicing and transition transition between the free-form surface and the general surface, and the curvature changes greatly. The processing method cannot be fully processed, so it must be processed in different regions according to the structural features. According to the characteristics, it is initially divided into nose processing area, fuselage processing area, wing processing area, vertical tail processing area, Airway processing area; Step 2. Process the back of the aircraft model according to the partitions of Step 1. The back of the model is more complicated than the front structure. Therefore, when the material has the best rigidity before cutting, it should be considered to process the back first, and the aircraft should be processed on the back. The back side of the model is processed with process bosses to improve the overall rigidity of the processing technology system; the process bosses enhance the processing rigidity and solve the thin-walled structure of the aircraft.

The flutter problem in the CNC machining process of parts, the process boss is located at the fuselage and wing of the aircraft model, and the cylindrical process boss at the fuselage is arranged in three-point type with the aircraft landing gear as the benchmark or two points in the longitudinal direction of the fuselage. Arrangement, the rectangular process boss at the wing is arranged symmetrically on both sides under the premise of enclosing the wingtip pitot tube with the wing tip as the boundary; step 3, respectively process the front of the aircraft model according to the partition of step 1; put step 2 The process boss in the machine is connected to the process plate by bolts, and the process plate is clamped and positioned on the machine tool by the process platen. When machining the vertical tail part, the vertical tail part belongs to the thin-walled cantilever structure, and flutter is very easy to occur during semi-finishing and finishing, so the roughing stops when only half of the height of the vertical tail is processed, and then semi-finishing and semi-finishing are used. After machining, finish machining is carried out directly; the machining rigidity of the unremoved material part of the vertical tail is fully utilized to enhance the strength of the cantilever part, ensuring no chatter during the cutting process, that is, "semi-finishing synchronization". Secondly, in the semi-finishing and finishing processes, the offset line of the vertical tail contour offset tool radius is used as the tool position path driving line, and the trajectory line is smoothed, and the trajectory line is controlled to travel in a spiral manner in the height direction to achieve The helical symmetrical cutting method of the cutting process is adopted. The processing method can not only reduce the number of times of knife lifting, but also improve the processing efficiency. The symmetrical method makes the residual stress in the machining process released symmetrically and evenly. Therefore, it ensures the stability of machining, controls the problem of machining deformation, and obtains high machining efficiency. The selection of tools in steps 2 and 3 depends on the machining method. The planning and roughing stage is mainly for the purpose of material removal. Therefore, the tool type can be a flat bottom milling cutter or a round nose milling cutter. The diameter of the tool is mainly selected based on the structure size of the aircraft model and the principle of reducing the tool size. The tool diameter ФD should be smaller than the model abdomen. The distance d between the air inlets, that is, ФD<d, can ensure that the tool cuts part of the aircraft model abdominal allowance during the milling process, and the tool overhang is based on the height h1 of the process boss, so as to reduce the number of tools as much as possible. The overhang outside the tool holder should be larger than the vertical tail height h2 during frontal machining, so the tool overhang L should be located at L∈Max(h1, h2) to ensure the stability of the cutting process. According to the planning of the machining method, the semi-finishing and finishing stages are mainly based on the machining dimensional accuracy and the geometrical accuracy of the free-form surface. Therefore, the tool type is a ball-end milling cutter, and the tool diameter is transitioned to the minimum radius R∈ of the free-form surface. Min(R1,R2,...Rn), (wherein, R1,R2,...Rn represents the transition radius value between all transition surfaces), the tool overhang and roughing for front semi-finishing and finishing The principle of machining selection is the same; in the selection of machine tools and fixtures in steps 2 and 3, the machine tool has no undercut surface and special-shaped surface in the entire aircraft model, and the machine tool adopts a three-axis CNC machine tool to meet the requirements. Axis CNC machining center improves processing efficiency and reduces auxiliary time such as manual tool change. Fixture selection, according to the planning of the processing method, adopts the overall numerical control processing, and the blank belongs to the processing of the rectangular blank. Therefore, the use of general-purpose machining center precision flat-nose pliers can meet the needs when machining the back. During frontal processing, a process plate has been produced, so a general-purpose process platen is used for frontal processing, which can meet the requirements by directly pressing it on the guide rail surface of the machine tool. The equipment and fixtures adopt a common form, which reduces the manufacturing cost, and also improves the processing efficiency and preparation cycle.