Design of the wedge-reversing punch die
The design of the wedge reversing die uses the wedge mechanism to convert the vertical movement of the press into a horizontal or inclined stamping movement. It is suitable for complex parts that require lateral punching, bending or cutting (such as automobile frame connectors, home appliance special-shaped brackets), and can complete multi-directional processing in one stamping stroke. The production efficiency is 40%-60% higher than that of traditional molds. The lateral stamping accuracy can reach ±0.05mm, and it is suitable for materials such as low-carbon steel and high-strength steel with a thickness of 2-8mm. The core is to achieve force reversal through the contact between the wedge and the inclined surface of the slider (the inclination angle is usually 30°-45°). The smaller the angle of the wedge, the greater the reversing force but the smaller the stroke; the larger the angle, the greater the stroke but the lower the force transmission efficiency. When designing, it is necessary to select a suitable angle according to the size of the lateral force (50-200kN).
The die structure consists of an active wedge, a driven slider, a lateral punch, a reset mechanism and a guide system. The active wedge is made of Cr12MoV steel with a quenching hardness of HRC58-62. The inclined surface is ground (flatness <0.01mm/m) and the surface is chrome-plated (thickness 0.01mm) to reduce the friction coefficient to below 0.15. The fit clearance between the driven slider and the active wedge is 0.01-0.03mm. A lateral punch (material W18Cr4V, HRC62-65) is installed on the slider. The angle between the punch axis and the horizontal direction can be designed according to the part requirements (0°-45°). The reset mechanism uses a nitrogen spring or a coil spring to provide sufficient reset force (10%-15% of the lateral force) to ensure that the slider returns to its initial position after stamping (position error <0.05mm).
Force transmission and stroke calculation must be accurate. According to the principle of mechanics, the lateral force Flateral = Fvert × tanα (Fvert is the vertical force of the press, α is the angle of the wedge). For example, a 30° wedge can generate a lateral force of 57.7kN under a vertical force of 100kN. The wedge stroke S oblique = Svert × sinα (Svert is the stroke of the press slide). When a lateral stroke of 10mm is required, a 30° wedge requires a vertical stroke of 20mm. To avoid force fluctuations, the contact surface between the active wedge and the driven slide must be well lubricated. Molybdenum disulfide grease (temperature resistance above 120°C) is used, and an oil storage tank (depth 0.5mm) is set to ensure sufficient lubrication during continuous stamping.
The guiding and positioning system ensures the commutation accuracy. A rectangular guide rail (width 20-50mm) is set at the bottom of the driven slider. The clearance between the guide rail and the slider is 0.005-0.01mm. The guide rail material is 40Cr quenched HRC50-55, and the surface grinding accuracy is Ra0.4μm. The parts are positioned in a combined positioning manner, with support blocks (accuracy ±0.05mm) for plane positioning and adjustable blocks for side positioning to ensure that the position error of the parts during lateral stamping is less than 0.1mm. For large parts (length > 500mm), 2-3 sets of wedge mechanisms are required to evenly distribute the lateral force and avoid part deformation (deflection < 0.3mm).
During commissioning and maintenance, attention should be paid to force balance. During mold trials, use a pressure sensor to measure lateral force. Deviation from the theoretically calculated value should be less than 5%. If the deviation is excessive, the contact surface of the wedge should be reground (removing 0.01mm at a time). After every 2000 cycles, inspect the guide rail for wear (adjust the shim if the clearance increases by more than 0.01mm). Polish the wedge bevel with fine sandpaper (400# grit) if scratches appear. During maintenance, regularly clean debris from the slider’s motion area. Perform monthly pressure checks on the nitrogen spring (replace if the deviation exceeds 10%) to ensure reliable reset.
