During the bending process of the press brake, due to the maximum stress at both ends of the slider, the reactive force during the bending of the sheet metal causes concave deformation on the lower surface of the slider, with the maximum deformation occurring in the middle part of the slider. To eliminate the adverse effects of slider deformation, it is necessary to compensate for the deflection deformation of the slider. Hydraulic compensation and mechanical compensation are used to induce upward elastic deformation in the middle of the worktable to counteract the deformation of the machine tool slider, ensuring the accuracy of the machining joint surface and improving workpiece precision.
Characteristics of mechanical compensation method:
Good flexibility, low cost, and the ability to achieve continuous deflection compensation.
In the case of using a hydraulic compensation mechanism, the CNC system automatically calculates the compensation amount based on the thickness, length of the bending material, and the selected mold, and outputs the corresponding analog voltage to the compensation amplification card. The amplification card amplifies the signal and controls the opening size of the hydraulic compensation proportional valve. From the moment the slider enters the slow descent state until it starts the return journey to the top dead center, the compensation proportional valve remains powered and operational. Changing the hold-down time of the slider at the machine tool's lower dead center may introduce errors in the processing accuracy of the bent workpiece under different hold-down times. Contaminants in the hydraulic oil can cause the hydraulic proportional valve spool to jam, leading to larger processing accuracy errors. As the compensation pressure is derived from the overall system pressure, when the compensation valve operates, there will be some pressure loss in the entire system. In the event of hydraulic oil control, incidents like oil pipe rupture, aging of the compensation cylinder seals, or loose connections can lead to oil leaks and contamination.
In the case of using a mechanical compensation mechanism, when the slider stops at the top dead center position, the CNC system automatically calculates the compensation amount based on the thickness, length of the bending material, and the selected mold. The system module controls the compensation motor's forward and reverse rotation to adjust the compensation deformation amount, and then feedback the changes in the upper and lower pad positions through a potentiometer. Once the compensation motor is adjusted, the compensation deformation amount does not change with variations in the hold-down time of the slider at the lower dead center, and there is no need to power it up each time the slider enters the slow descent, thereby preventing energy loss in the entire system. Since there are no hydraulic pipelines involved, there is no oil leakage or contamination. The machine tool functions as a unified worktable, saving manufacturing costs.
