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When the bending machine starts to bend, the beam and the worktable of the bending machine need to bear a load, and the load will cause the worktable and the beam to have a certain deformation. In order to achieve the precise bending and repeated forming effect, this When we need to add a deflection compensation to the bending machine system. Without deflection compensation, when the workpiece is bent along the entire worktable, its center may be deformed in some form. Especially for CNC bending machines with a length of more than 2.4 meters and a bending machine pressure of more than 80 tons, in order to maintain the consistency of the overall bending angle of the whole work, we need to install this kind of deflection compensation for the bending machine.
Most of the current CNC bending machine systems use a complete closed-loop servo-hydraulic CNC system to control the position of the working beam of the bending machine. At both ends of the working beam, there is a position controller at the lower end of the left and right oil cylinders to accurately monitor and control the lifting position of the oil cylinders. By having a servo valve on the top of each cylinder to enter the work, the controllable accuracy can reach 0.01mm. In a bending, the servo hydraulic system controls the programmed data to ensure that the cylinder reaches an accurate position so that the bending workpiece reaches the correct angle. However, the bending machine tends to deform under load, especially at the center of the machine tool, so that the bending angle of the workpiece at the center of the machine tool will be different from the two ends. If there is no interference, this angle error will increase as the length of the bending machine becomes larger. In order to compensate, we usually install a convex device to balance the bending error by generating a force opposite to the deflection. We call the left and right of the convex device the crowning system.
The crowning system was applied to the field of bending machines as early as the 1980s. This crowning system is usually installed in the field of large-scale bending and high-strength bending, because the misunderstanding of large-scale bending deflection is relatively large. Before the compensation system was invented, some bending machine manufacturers used a convex worktable to control the compensation, and this crowning could only reach 75% at most. Now, as the numerical control system becomes more and more perfect, through the bending crowning system controlled by the numerical control system, the operator only needs to input some data such as the length, thickness and material yield strength of the sheet metal, and the system will automatically calculate the crowning amount And decided to give an accurate compensation amount to the bending machine worktable, the system stores these data, and only need to call the data repeatedly during repeated bending work.
The crowning system is generally applied to CNC bending machines with a length of more than 2.4 meters and a press brake of more than 80 tons. However, some small bending machines are now equipped with crowning systems. It depends on the length of the workbench and the application scenario.
Hydraulic crowning and mechanical crowning are the two crowning methods we usually see, and they are also the most widely used. Mechanical crowning can be added as an optional device for the bending machine, while hydraulic crowning is a device integrated inside the machine tool and is not optional.
In the bending process, the hydraulic crowning system transmits pressure to the compensation cylinder through hydraulic pressure, so that the machine tool table produces compensation deformation.
However, this hydraulic crowning system cannot compensate the entire workbench, and the amount of partial compensation depends on the position of the compensation cylinder. Some hydraulic crowning bending machines only have a compensation cylinder at the center of the machine tool, and there are also multi-cylinder systems. All oil cylinders share a pressure system, so it will not be said that only one oil cylinder produces pressure compensation. This pressure will generate compensation pressure for each oil cylinder.
The mechanical crowning system is composed of two rows of convex devices. One row is fixed and the other row is movable. The wedge in the middle has a higher slope than the wedge below the piston of the cylinder, and the slope angle follows the direction of the bed to both sides. slowing shrieking. After starting to work, move the wedge to create a curve, the high point is located in the center of the bed, the low point is located at either end of the bed, under the cylinder piston, above the table to create a spline curve, the compensation system works according to the bed like this The deformation of the platform and the beam is automatically compensated.
In the mechanical crowning system, the load on the worktable depends on the tonnage requirements of the machine tool. The accuracy of some CNC mechanical crowning systems can be set to ±0.01mm and the repeat error is within the range of ±0.005mm. The mechanical crowning device can realize compensation along the entire length of the machine tool. It can also handle deflection compensation for higher tonnage and shorter bed lengths. In addition, with the development of the mechanical compensation system, the mechanical compensation system has a complete standard, which can be separately manufactured and matched. It can be edited and operated by the CNC system. An ordinary bending machine can be easily equipped with a mechanical compensation device to improve its performance, and it can also be installed on a smaller tonnage entry-level bending machine for better use by the operator.
In order to ensure the consistency of the bending angle of the entire workpiece, the crowning system reduces the trouble of the operator and minimizes the defective rate of the product. If there is no crowningsystem, you can only use gaskets or adjust the mold to control the deflection in the bending work. Calculating the number of gaskets is often time-consuming, laborious and error-prone. Even experienced operators will often scrap the work piece because of the failure to calculate the number of shims. The CNC bending crowningsystem is calculated by computer programming, which reduces the level of skills required to operate the machine, thereby increasing efficiency and productivity.
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