Milling of arc surface and positioning groove of aircraft wing

3. Homemade milling cutter

Machining of the positioning groove on the airfoil, the groove depth is 21.1mm, the groove length is 280mm, and the groove width is 6 +0.075 0  mm. The slot is used for the assembly and positioning of the wing surface and the aircraft cabin. The size of the slot bottom must be R30mm. The required milling cutter cannot be purchased in the market. A special shank carbide three-sided edge milling cutter (see Figure 2) is self-made. The diameter of the tool holder is 16mm, the diameter of the milling cutter is 60 mm, and the thickness is 5mm. The material of the cutter head is YG. The rake angle of the milling cutter is γ o =3°, the relief angle is α o =8°, and the radius of the tip arc is 0.5mm. The accuracy requirement of the groove bottom dimension R30mm is well guaranteed.

4. Self-control jig

Since the two sides of the airfoil are inclined surfaces, a special fixture must be selected for clamping, so a special fixture is made by yourself (see Figure 3). The main points of fixture design: the clamp body has to withstand a large cutting force, so it must have sufficient strength, rigidity and stability. The mounting surface of the clamp should be large enough, and be made into a form of peripheral contact as much as possible. Milling machine fixtures usually determine the position of the fixture on the machine tool through the cooperation of the positioning key and the T-slot of the milling machine table. H7/h6 are mostly used for the specific coordination of positioning keys and clamps. In order to improve the installation accuracy of the fixture, the lower part of the positioning key (the part that matches the T-slot of the worktable) can be left for repair, or when the fixture is installed, the side of the positioning key should be close to the T-slot of the worktable to eliminate The effect of the gap. The milling machine clamp is provided with an ear seat on the clamp body, and the clamp is firmly fastened in the T-shaped groove of the machine tool table through bolts.

5. Milling machine adjustment and clamping correction

Figure 3 Self-made special fixture

According to the drawing requirements, in order to ensure the machining accuracy of the parts, it is necessary to adjust the non-perpendicularity of the milling head and the work surface. Through actual measurement, the error of the non-perpendicularity of the end milling head and the work surface is 0.1mm/300mm. Through calculation and adjustment, the angle of the end milling head is ensured to control the non-perpendicularity error of the workpiece table to within 0.02mm/300mm. The two points are corrected by using a dial indicator, as shown in Figure 3, to make it parallel to the working table. , And use four pressing plates to compress the workpiece for milling processing. During processing, the asymmetry of the 6mm slot and 20mm is controlled by using a lever meter to make it within 0.03mm, ensuring the asymmetry of the slot width and the reference plane, so that the parts can meet the drawing requirements.

6. Conclusion

The part has irregular shape, difficult clamping, high tolerance requirements, poor material cutting performance, difficult machining of some cavities and no ready-made tools. Through reasonable fixture design, the design and manufacture of special forming tools, and the adjustment of machine tools and fixtures, the cavity processing was successfully completed and the design tolerance requirements of the parts were ensured. In view of the low production efficiency and the inability to guarantee timely delivery, the process route was reasonably changed through the restructuring of the cutting tools and milling instead of boring. While ensuring the tolerance requirements of the parts, the production efficiency was improved and the machining accuracy of the parts was ensured. Claim.