Key points of CNC milling of large titanium alloy fan blade profile
According to the overall technical idea of ​​the blade profile, the milling of the blade profile must ensure that the geometrical position accuracy of the profile meets the design requirements and has a certain surface roughness quality. At the same time, the improvement of machining efficiency is also the focus of profile milling. One of the jobs. According to the understanding of the processing characteristics of the large titanium alloy fan blade profile, it is necessary to comprehensively consider the influence of various factors such as equipment, tools, and machining positioning.
For the milling of large titanium alloy fan blade profiles, it is necessary to select a five-axis machining center. The choice of a mature five-axis linkage blade machining center has both high-efficiency machining considerations and machining accuracy assurance capabilities. For the profile machining with large curvature change, the swing angle function of the machine tool spindle can well adapt to the requirement of the same cutting force corresponding to the curvature change of the profile surface. The high pressure cooling system of the machine tool greatly reduces the cutting temperature and avoids the rapid wear of the tool. , to make the surface processing to obtain good processing precision and surface processing quality.
In order to prevent and reduce the torsional deformation caused by long blade clamping and cutting, it is necessary to ensure that the rotary shaft of the front and rear end of the device has a synchronous rotation function, the purpose of which is to change the end of the conventional blade processing process to clamp, one end top The tight positioning and clamping method avoids the bending deformation generated when the blade is clamped and the one end rotates when the blade is rotated, and the one end follows the torsional deformation of the blade profile in the longitudinal direction. Applicable to this requirement of blade positioning and clamping, the auxiliary positioning part of the blade tail end has strict positional accuracy requirements with respect to the front end of the boring head. After the roughing of the profile is completed, the blade is generated before and after the roughing of the profile. The positional accuracy error between the end positioning datums is to be repaired. The blade profile processing jig is used to detect and adjust the mounting accuracy of the front and rear clamps by using a special mandrel after the front and rear rotary axes of the machine are mounted on the rotary axes of the front and rear ends of the machine. Ensure that the clamps at both ends have an accurate positional accuracy relationship, so as to avoid the additional torsional stress caused by the poor clamping accuracy of the front and rear rotary axes of the machine.
The rough milling of the blade profile is to remove a large margin and leave a uniform machining allowance for finishing. Under this premise, the machining of this process should ensure high machining efficiency. The five-axis linkage blade machining center has a wide-line machining function. The principle is that when milling the blade, the tool center line is not perpendicular to the tangent of the milled point or face, but in the direction of the pass and the point or face being milled. The normal direction is a certain angle. This type of milling uses a cylindrical end mill. The milling path is a wide elliptical arc. Compared to the milling of the ball-end knife, the same profile peak height or surface is milled. In terms of quality, the distance between the generated tool paths is much larger. Therefore, this processing has high processing efficiency. In the actual machining, a rotary machining method in which the length of the blade moves from one end to the other end, that is, a spiral milling method, the spiral milling method has a higher processing efficiency than the longitudinal milling method from the viewpoint of efficiency.
The finishing of the blade profile is to achieve high geometric and positional accuracy, while at the same time achieving a certain level of roughness of the profile. In order to reduce the "rebound" effect of titanium alloy material processing and the influence of tool wear on machining accuracy during large-area profile machining, the tool must be sharp and avoid long-term machining of a tool. For this reason, if possible, use end mills for longitudinal milling of the profile. Longitudinal milling can use several tools to mill the blade back profile, the blade profile, the intake edge and the exhaust edge, avoiding the wear caused by the large-area machining of a tool. The inconsistency is conducive to the final finishing of the surface.
In order to improve the cutting conditions during large-scale titanium alloy fan rotor blade profile milling, all measures to avoid tool wear are necessary. In the selection of tool materials and specifications, the choice of solid carbide coated cylindrical ball milling cutter for machining the inner side of the blade edge plate, the inner side of the edge plate and the transition surface of the profile transfer arc, close to the edge plate At the edge of the inlet and outlet, the end mill with a cylindrical carbide-coated blade is used to machine the blade surface of the blade and the large surface of the blade back. The choice of coating material for processing titanium alloy tools is very important, avoiding the use of coating materials with affinity to titanium alloys. At present, PVD coated tools are commonly used in the processing of titanium alloys. The PVD coatings are thin and smooth. They adhere to the cemented carbide substrate and produce a residual stress, which is beneficial to improve the damage resistance of the tool. PVD It can be closely attached to the tool, which is good for maintaining the sharp cutting edge shape. The PVD tool has good abrasion resistance, chemical stability and is not easy to produce built-up edge. In the process, use sufficient coolant to cool the tool and improve the friction effect, select reasonable cutting parameters, and improve the influence of cutting force.
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