Bullet Mandrel The Bullet Mandrel is a mandrel bracket, the φ 10 hole is equipped with a mandrel, and the trailer is connected to the fuselage through four 5 holes. The parts are symmetrical and the 5 holes have higher precision requirements. The part is made of No. 08 cold-rolled steel plate,...
The Bullet Mandrel is a mandrel bracket, the φ 10 hole is equipped with a mandrel, and the trailer is connected to the fuselage through four 5 holes. The parts are symmetrical and the 5 holes have higher precision requirements. The part is made of No. 08 cold-rolled steel plate, and its bending radius is larger than the minimum bending radius of the material (R1.5>0.8t), and 5 holes can also be punched out as required. Therefore, the part is suitable for cold stamping. The basic processes for stamping the part are: punching, blanking and bending.
1. To simplify the mold structure, the holes in the part should be punched out as much as possible on the flat blank. The distance between the middle 10 hole side and the bending center on the part is 6mm, which is larger than 1.0t=1 5mm, and does not cause deformation of the hole when bending. Therefore, the φ 10 hole can be punched out before the bending. The φ 10+0.08 hole punched out can be used as a positioning hole for the subsequent process. The distance between the edge of the 4-φ5 hole and the center of the bend is 1.5 mm, which is equal to 1.0 t. The deformation of the hole is likely to occur during the bending, so it should be punched out after bending.
2. The first method has the advantage of forming with a pair of molds, high productivity and less equipment occupation. The disadvantages are: (1) The mold wears fast and the life is low, because the entire area of the blank is almost involved in the intense bending deformation, and requires a large bending force: (2) the surface of the workpiece is easily scratched, and the scratch area is also large; 3) The shape and size of the workpiece are not accurate; the material at the corner is thin and severe. This is because the bending cannot be effectively utilized or the bending is corrected to control the rebound, which has been caused by the large resistance at the rounded corners of the convex and concave molds.
3. The second method uses two pairs of molds to bend twice. First bend the ends of the two corners. Then press out the middle corner. Obviously, the bending deformation is much more intense than the first method, the bending force is also small, and the working conditions of the mold are greatly improved. However, the rebound phenomenon is still difficult to control and increases the number of molds, presses and operators.
4. The third method is to first bend the two corners of a pair of molds while pre-bending the middle corners to make it 45°, and then bend the middle corners to 90° on the other pair of molds. Since the over-bending and the correcting of the bending can be achieved, the springback of the workpiece can be easily controlled, and parts having a precise shape and size can be obtained. In addition, since the material is convex during the forming process, the resistance of the die is small, the workpiece can be obtained with a good surface quality, and the life of the mold can be improved.