Design of Double-Wedge Bending Die
The double-wedge bending die design is an efficient forming technology developed for complex multi-directional bending parts (such as car seat frames and hardware brackets). Through the wedge drive mechanism in two directions, the parts can be bent synchronously in the horizontal and vertical directions. The forming angle can reach 90°-135° at one time, and the angle error is less than 0.5°. It is suitable for Q235, Q345 and other steels with a thickness of 1-5mm. Compared with the single-wedge die, its core advantage is that it can complete symmetrical or asymmetrical bidirectional bending, reduce process flow, and improve production efficiency by more than 40%. In the early stage of design, the angle of the wedge needs to be determined according to the bending angle and material thickness. It is usually 30°-45°. The 30° wedge is suitable for large bending forces (≥50kN), and the 45° wedge is suitable for rapid forming (speed ≥100mm/s).
The mold structure consists of an upper die base, active cam, left and right driven cams, a bending punch, a bending die, and a reset mechanism. The active cam is made of Cr12MoV steel, hardened to HRC 58-62. The bevel is ground (flatness <0.01mm/m) and chrome-plated (0.01mm thickness) to reduce the friction coefficient to below 0.15. The left and right driven cams have a clearance of 0.01-0.03mm relative to the active cam, respectively driving the bending punches on either side. The working portion of the punch is designed according to the part's bending radius (typically 1-3 times the material thickness). For 2mm thick parts, the bending radius is set at 2-6mm to prevent cracking during bending. The reset mechanism uses a nitrogen spring, providing a reset force of 10-20kN, ensuring precise reset of the cam during the return stroke (position error <0.05mm).
Force transmission and distribution are the key to the coordinated work of the double wedges. The active wedge converts the vertical force (100-200kN) of the press into a horizontal force component. The force component is calculated according to the formula F=F total × sinα (α is the angle of the wedge). The horizontal force component of the 30° wedge is 50% of the total force, and the 45° wedge is 70.7%. By adjusting the contact area of the driven wedges on both sides, the force distribution of asymmetric bending can be achieved, such as 60kN on the left and 40kN on the right, to meet the forming requirements of different bending parts. The bending die adopts a split insert design. The insert material is cemented carbide (YG15). The surface roughness of the surface in contact with the part is Ra0.8μm or less, ensuring that there are no scratches on the bending surface.
The guide and limit system ensures the bending accuracy. A guide rail (width 20-50mm) is set at the bottom of the driven wedge. The clearance between the rail and the wedge is 0.01-0.02mm to limit the lateral deviation of the wedge. The bending stroke is precisely controlled by the limit block, with a stroke error of ±0.05mm to ensure consistent bending height (deviation <0.1mm). For asymmetric bending parts, limit columns of different lengths need to be set on both sides of the mold to compensate for the difference in bending deformation on both sides. For example, the bending height on the left is 10mm and on the right is 8mm, and the corresponding difference in the length of the limit column is 2mm.
During debugging and maintenance, attention should be paid to the wedge matching accuracy. During the mold test, the bending angles on both sides should be measured. If the difference is greater than 1°, the thickness of the driven wedge should be repaired (0.01mm each time) to adjust the force distribution. After every 2,000 operations, clean the iron filings on the contact surface of the wedge and apply molybdenum disulfide grease (temperature resistant to 150°C); the nitrogen spring of the reset mechanism should be tested for pressure every six months and replaced when the deviation exceeds 10%. When the mold is stored, the wedge should be reset to its initial position to avoid long-term deformation due to stress. A 0.1mm thick anti-rust paper should be placed between the driven wedge and the slide rail to prevent rust and jamming.
