How to adjust the hydraulic cushion force to prevent denting in automobile cover hydraulic press processing?
Release Time : 2025-09-04
In automobile cover hydraulic press processing, adjusting the hydraulic cushioning force is crucial for preventing surface sinking on parts. This sinking problem often occurs in the center of the part, primarily due to insufficient plastic deformation in the material, resulting in poor rigidity. Insufficient or unevenly distributed hydraulic cushioning force can exacerbate this phenomenon. Therefore, systematic adjustment of the hydraulic cushioning force, combined with mold structure optimization and process parameter control, is necessary to achieve uniform material deformation and thus improve part quality.
The core function of the hydraulic cushioning force is to apply uniform pressure to the blank through the blank holder, suppressing variations in material flow velocity during the drawing process. Insufficient hydraulic cushioning force will cause material around the blank to flow too quickly into the die, resulting in insufficient stretching in the center and forming a sinking effect. Conversely, excessive pressure can cause material cracking or localized thinning. Therefore, precise hydraulic cushioning force must be set based on part shape, material properties, and mold structure. For example, for large covering parts like hood panels, the inner contour of the die has minimal curvature variation and is predominantly straight. Rapid material feed is only required in localized areas (such as the four corners). In this case, continuous or intermittent drawbeads are placed along the die opening, combined with hydraulic cushioning force adjustment to control material flow, create bulging in the center, and enhance rigidity.
Adjusting hydraulic cushioning force requires integration with mold structure optimization. Drawbeads are key components for controlling material flow, and their type and layout directly impact the effectiveness of hydraulic cushioning. Round beading is suitable for applications with high material flow, offering ease of mold repair and flexible resistance adjustment. Rectangular beading is used for applications with low material flow or when bulging is required, providing stronger additional tension. In automobile cover hydraulic press processing, switching from round drawbeads to rectangular beading and adding double rectangular beading at the rear increases material feed resistance, reduces material flow, and allows for plastic deformation in the center under the hydraulic cushioning force, eliminating dents. Adjusting the position and number of drawbeads can also optimize the distribution of hydraulic cushioning force. For example, intermittent drawbeads are placed along the die opening, but not at the bends. This can adjust for differences in material deformation across the blanking surface, ensuring uniform material flow into the die and avoiding sinking caused by excessive local pressure.
Coordinated adjustment of process parameters is equally important. While maintaining constant master cylinder pressure and hold time, the optimal hydraulic pressure must be determined through experimentation. For example, in the hydraulic press processing of an automobile cover outer panel, the hydraulic pressure was initially set to the upper limit of process requirements, but part strength did not improve. Later, the pressure was increased to a higher value, exceeding the process range. However, optimization of the die structure (such as adjusting drawbeads and increasing material width) ultimately resulted in plastic deformation in the center section, significantly improving strength. Furthermore, the parallelism of the hydraulic pad must be strictly controlled. If the hydraulic pad guide plate is perpendicular to the fixed worktable guide plate, the hydraulic pad will tilt, resulting in uneven distribution of the blank holding force and, in turn, sinking. Therefore, it is necessary to adjust the guide rail gap, use adjustable guide rails, or optimize the guide plate structure to ensure the hydraulic pad's movement accuracy and evenly transmit the blank holding force to the blank.
In actual automobile cover hydraulic press processing, dynamic adjustments must be made based on part shape and material properties. For example, for areas with significant differences in shaping line length (such as the rear of a car's roof), it is necessary to increase the pressing force of the positive pressure core, modify the part shape, or adjust the drawing die process to add surface radius to reduce internal stress variations in the sheet and avoid sinking. Furthermore, regular inspection of the hydraulic pad's seal and lubrication status to prevent pressure fluctuations caused by oil leakage or increased friction is also a key measure to ensure the stability of automobile cover hydraulic press processing.
