Design of Rotating Shaft Bending Die
The pivot-type bending die design is a specialized technology for bending various rod-shaped and plate-shaped parts, such as furniture brackets and mechanical connecting rods. The bending is achieved through the rotation of a pivot. Suitable for materials with thicknesses ranging from 1-8mm for mild steel and stainless steel, it can achieve bending angles of 0° to 180° with an angle accuracy of ±0.5° and a bending radius accuracy of ±0.1mm. Its core principle is to utilize the fixed axis of the pivot to ensure the precise positioning of the bend center and prevent part deviation during the bending process. This technology is particularly suitable for parts requiring multiple or symmetrical bends, and it improves production efficiency by 30%-50% compared to traditional bending dies. Initially, the pivot diameter (typically 2-3 times the bend radius) and the rotation angle range must be determined based on the part’s bend radius and angle.
The mold structure consists of a rotating shaft, a positioning block, a clamping device, a limit mechanism and a drive system. The rotating shaft is made of 40Cr steel, with a quenching hardness of HRC45-50 and a chrome-plated surface (thickness 0.01mm) to improve wear resistance. The diameter of the working part of the rotating shaft is designed according to the bending radius (deviation ±0.05mm), and the surface roughness in contact with the part is Ra0.8μm or less. The positioning block is used to determine the bending position of the part. It is welded with Q235 steel and a wear-resistant plate (45 steel quenched HRC40-45) is installed on the surface. The positioning accuracy is ±0.1mm. The clamping device is pneumatically or hydraulically driven, which can provide sufficient clamping force (5-20kN) to ensure that the part does not slide during the bending process, and the shape of the clamping block fits the surface of the part (fitting degree > 90%).
The bending process parameters need to be optimized according to the material and bending requirements. The bending speed is controlled at 10°-30°/second. A higher speed can be used for low-carbon steel, and a lower speed is required for stainless steel to avoid material cracking. For parts with a bending angle of >90°, step-by-step bending is required. First bend to an angle close to the required angle (such as 100° to 95°), and then perform shaping (to 100°) to reduce springback. For parts with a bending radius less than 2 times the material thickness, the bending part needs to be locally heated before bending (600-650°C for low-carbon steel) to reduce the yield strength of the material and avoid cracks during bending.
The drive and limit system ensures bending accuracy. The drive system uses a servo motor to drive the reducer to drive the rotating shaft. The rotation angle control accuracy is ±0.1°, and multi-speed control can be achieved (different speeds in the startup, bending, and shaping stages). The limit mechanism consists of a mechanical stop and a photoelectric sensor. The mechanical stop is used to limit the maximum bending angle (error ±0.2°). The photoelectric sensor monitors the position of the rotating shaft in real time and feeds back to the control system to achieve closed-loop control. For parts that require symmetrical bending, two symmetrical rotating shafts are set up and driven by the same drive system to ensure that the bending angles on both sides are consistent (deviation <0.3°).
During commissioning and maintenance, pay attention to shaft precision control. During mold trials, measure the bending angle and radius of the parts. Sample 10 parts per batch. If the angle is out of tolerance, adjust the limit stop (±0.1mm). If the radius is out of tolerance (>0.1mm), replace the shaft. After every 1000 cycles, check the shaft’s rotational clearance (adjust the bearing if the deviation is >0.05mm), clean the locating block from iron filings and oil, and lubricate the rotating shaft area with grease (NLGI grade 2). During long-term storage, rotate the shaft to its initial position, apply anti-rust oil to the locating block and pressure block, disconnect the drive system from power, and perform dust protection. Manually rotate the shaft regularly (quarterly) to prevent bearing rust and seizure.
