CNC bending machines are important equipment in sheet metal processing, and their working precision directly affects the accuracy of the bent workpieces. During the bending process, the bending machine experiences deformation due to the maximum forces acting on the ends of the slide block. This deformation results in concave deformation on the lower surface of the slide block, with the maximum deformation occurring in the middle section. Consequently, the angles of the bent workpieces vary along their entire length. To eliminate the adverse effects of slide block deformation, it is necessary to compensate for the deflection. Two common compensation methods are hydraulic compensation and mechanical compensation, both of which aim to create upward elastic deformation in the middle section of the worktable to counteract the deformation of the machine's slide block. This ensures the accuracy of the machining interface and improves the precision of the workpiece. Currently, major machine tool manufacturers choose the appropriate compensation method based on the specific circumstances.
Introduction to the Two Compensation Methods:
1. Hydraulic Compensation Method:
The hydraulic automatic deflection compensation mechanism of the worktable consists of a group of oil cylinders installed in the lower worktable. The position and size of each compensation cylinder are designed based on the deflection compensation curve obtained from finite element analysis of the slide block and worktable. Hydraulic compensation is achieved through the relative displacement between the front, middle, and rear vertical plates, resulting in an upward convex compensation. The principle is based on the elastic deformation of the steel plate itself, allowing for compensation within the elastic range of the worktable.
2. Mechanical Compensation Method:
The mechanical compensation method consists of a set of wedge blocks with inclined surfaces. Each wedge block is designed based on the deflection curve obtained from finite element analysis of the slide block and worktable. The CNC system calculates the required compensation amount based on the magnitude of the load force during workpiece bending, which causes deflection deformation in the slide block and worktable vertical plates. It automatically controls the relative movement of the wedge blocks to effectively compensate for the deflection deformation of the slide block and worktable. This method achieves the desired mechanical deflection compensation by controlling the position. The wedge blocks form a curve that matches the actual deflection along the length of the worktable, ensuring consistent gaps between the upper and lower dies during bending and ensuring consistent angles of the workpiece in the length direction.
Comparison of the Two Compensation Methods:
Advantages of Hydraulic Compensation:
- Over time, hydraulic compensation does not experience wear and tear issues, unlike mechanical compensation where components like screws and wedge blocks may wear out.
- Hydraulic compensation requires less space, while mechanical compensation occupies more free space in both height and width directions.
- During hydraulic compensation, the workpiece cannot experience displacement because the lower worktable remains in a flat state, in contact with the ground, providing stable support when the upper beam contacts the workpiece. Mechanical compensation, on the other hand, only comes into effect after bending and may introduce unpredictable errors.
- Hydraulic compensation can be adjusted even when the workpiece is not removed, while mechanical compensation does not allow for such adjustments.
Advantages of Mechanical Compensation:
- Mechanical compensation provides long-term stability and durability, reducing the maintenance difficulty and frequency associated with hydraulic compensation (such as oil leakage caused by seal damage). It requires no maintenance during the machine tool's lifespan.
- Mechanical compensation allows for precise deflection compensation along the entire length of the worktable due to multiple compensation points. This ensures more linear compensation and improves the bending effect of the workpiece.
- Mechanical compensation uses a potentiometer to measure the return signal position, enabling digital control as a CNC axis. This results in more precise compensation values.
Introduction to the Two Compensation Methods:
1. Hydraulic Compensation Method:
The hydraulic automatic deflection compensation mechanism of the worktable consists of a group of oil cylinders installed in the lower worktable. The position and size of each compensation cylinder are designed based on the deflection compensation curve obtained from finite element analysis of the slide block and worktable. Hydraulic compensation is achieved through the relative displacement between the front, middle, and rear vertical plates, resulting in an upward convex compensation. The principle is based on the elastic deformation of the steel plate itself, allowing for compensation within the elastic range of the worktable.
2. Mechanical Compensation Method:
The mechanical compensation method consists of a set of wedge blocks with inclined surfaces. Each wedge block is designed based on the deflection curve obtained from finite element analysis of the slide block and worktable. The CNC system calculates the required compensation amount based on the magnitude of the load force during workpiece bending, which causes deflection deformation in the slide block and worktable vertical plates. It automatically controls the relative movement of the wedge blocks to effectively compensate for the deflection deformation of the slide block and worktable. This method achieves the desired mechanical deflection compensation by controlling the position. The wedge blocks form a curve that matches the actual deflection along the length of the worktable, ensuring consistent gaps between the upper and lower dies during bending and ensuring consistent angles of the workpiece in the length direction.
Comparison of the Two Compensation Methods:
Advantages of Hydraulic Compensation:
- Over time, hydraulic compensation does not experience wear and tear issues, unlike mechanical compensation where components like screws and wedge blocks may wear out.
- Hydraulic compensation requires less space, while mechanical compensation occupies more free space in both height and width directions.
- During hydraulic compensation, the workpiece cannot experience displacement because the lower worktable remains in a flat state, in contact with the ground, providing stable support when the upper beam contacts the workpiece. Mechanical compensation, on the other hand, only comes into effect after bending and may introduce unpredictable errors.
- Hydraulic compensation can be adjusted even when the workpiece is not removed, while mechanical compensation does not allow for such adjustments.
Advantages of Mechanical Compensation:
- Mechanical compensation provides long-term stability and durability, reducing the maintenance difficulty and frequency associated with hydraulic compensation (such as oil leakage caused by seal damage). It requires no maintenance during the machine tool's lifespan.
- Mechanical compensation allows for precise deflection compensation along the entire length of the worktable due to multiple compensation points. This ensures more linear compensation and improves the bending effect of the workpiece.
- Mechanical compensation uses a potentiometer to measure the return signal position, enabling digital control as a CNC axis. This results in more precise compensation values.
