Five-axis linkage machining center milling titanium alloy fan blade profile

According to the overall process requirements of the blade profile, the milling process of the blade profile must ensure that the geometric position accuracy of the profile basically meets the design requirements and has a certain surface roughness quality. At the same time, improving the efficiency during processing is also the focus of profile milling. One of the jobs. Based on the understanding of the processing characteristics of large titanium alloy fan blades, it is necessary to comprehensively consider the influence of various factors such as equipment, cutting tools, and processing positioning.

For the milling of large titanium alloy fan blade profiles, it is very necessary to choose a five-axis linkage machining center. Choosing a mature five-axis linkage blade machining center involves both efficient processing and machining accuracy assurance capabilities. For the processing of profiles with large curvature changes, the swing angle function of the machine tool spindle can well adapt to the requirements for consistent cutting stress corresponding to changes in profile curvature. The high-pressure cooling system of the machine tool greatly reduces the cutting temperature and avoids rapid tool wear. , so that the profile processing can obtain good processing accuracy and surface processing quality.

1. Blade clamping method

In order to prevent and reduce the torsional deformation produced during the clamping and cutting of long blades, it is necessary to ensure that the rotary shafts for clamping the blades at the front and rear ends of the equipment have synchronous rotation functions. The purpose is to change the traditional blade processing technology of one end clamping and one end pushing. The tight positioning and clamping method avoids the bending deformation caused when the blade is clamped and the torsional deformation of the blade profile in the length direction caused by one end rotating and the other end following the blade rotation processing. To adapt to the requirements of blade positioning and clamping, the auxiliary positioning part at the tail end of the blade must have strict position accuracy requirements relative to the tenon positioning datum at the front end. After the rough machining of the profile is completed, the front and rear parts of the blade caused by stress deformation must be The position accuracy error between the end positioning datums must be repaired.

After the fixture for blade profile processing is installed on the rotary axes at the front and rear ends of the machine tool, and after confirming that there is no concentricity error in the rotary axes at the front and rear ends of the machine tool, a special mandrel is used to detect and adjust the installation accuracy of the front and rear fixtures. Ensure that the clamps at both ends have an accurate positional accuracy relationship to prevent the synchronous rotation function of the front and rear rotary axes of the machine tool from generating additional torsional stress due to poor clamping accuracy.

2. Rough milling of blade profile

In order to remove a large allowance and leave a uniform machining allowance for finishing, under this premise, the processing of this process should ensure high processing efficiency. The five-axis linkage blade machining center has a wide-row machining function. The principle is that when milling blades, the center line of the tool is not perpendicular to the tangent line of the point or surface to be milled, but is in line with the point or surface to be milled in the direction of tool movement. The normal direction is at a certain angle. This type of milling uses a cylindrical end mill, and the milling trajectory is a wider elliptical arc. Compared with the milling of a ball-nose cutter, the same profile crest height or surface can be milled. Quality-wise, the resulting toolpaths are much more widely spaced. Therefore, this kind of processing has high processing efficiency. In actual processing, the rotary processing method is used to move from one end to the other end along the length of the blade, that is, the spiral milling method. From an efficiency perspective, the spiral milling method also has higher processing efficiency than the longitudinal milling method.

3. Fine milling of blade profile

In order to obtain higher geometric and positional accuracy, and at the same time make the roughness level of the profile meet certain requirements. In order to reduce the “springback” effect caused by titanium alloy material processing and the impact of tool wear on processing accuracy when processing large-area profiles, the tool must be sharp and avoid long-term processing of one tool. For this reason, when possible, try to use end mills for longitudinal milling of the profile. For longitudinal milling, several tools can be used to mill the blade back surface, blade basin surface, intake edge, and exhaust edge to avoid the wear caused by large-area processing with one tool, which will affect the accuracy of the processing of various parts of the blade. The phenomenon of inconsistency is beneficial to the final finishing of the profile.

In order to improve cutting conditions when milling large titanium alloy fan rotor blades, all measures to avoid tool wear are necessary. In terms of the selection of tool materials and specifications, a solid carbide coated cylindrical ball milling cutter is selected to process the inner surface of the blade edge plate, the transition arc between the inner surface of the edge plate and the profile, and the transition profile close to the edge plate. , at the edge of the intake and exhaust, choose an end mill with a cylindrical carbide-coated blade to process the large surface of the blade basin and blade back. The selection of coating materials for machining titanium alloy tools is very important. Avoid using coating materials that have affinity with titanium alloys. At present, PVD-coated tools are commonly used for machining titanium alloys. The PVD coatings are thin and smooth. When they adhere to the carbide substrate of the tool, they also generate a residual stress. This stress is conducive to improving the damage resistance of the tool. PVD It can be closely attached to the tool, which is helpful to maintain a sharp cutting edge shape. PVD tools have good wear resistance, stable chemical properties, and are not prone to built-up edges. During processing, it is necessary to use sufficient coolant to cool the tool and improve the friction effect, select reasonable cutting processing parameters, and improve the effect of cutting force.

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