Pneumatic System Design of Bending Machine

In my journey through the world of metal fabrication, I have gained valuable insights into the pneumatic system design of bending machines. Pneumatic systems play a crucial role in enhancing the efficiency and precision of bending processes by utilizing compressed air to operate various components. Understanding the intricacies of pneumatic system design is essential for optimizing performance and ensuring reliable operation. Over the years, I have explored the key elements of these systems, including actuators, valves, and control mechanisms. In this article, I will share my knowledge on the pneumatic system design of bending machines, highlighting its importance and practical applications in the industry.

Bending is a method of bending various metal blanks into a certain angle, radius of curvature and shape. The bending machine is a special equipment for sheet bending. Due to its simple operation and good versatility, it is widely used in the sheet metal processing industry. At present, the bending machine mostly adopts hydraulic system.

Although the hydraulic system can achieve higher pressure and the transmission is relatively stable, the leakage problem of the hydraulic system can not be ignored, which is easy to cause environmental pollution, and the hydraulic system is difficult to troubleshoot, and the maintenance personnel are required to compare. high. Relatively speaking, the pneumatic system is air-free, has no cost, and does not cause pollution when discharged into the atmosphere. Moreover, the maintenance is simple and convenient, the pipeline is not easy to be blocked, the use is safe and reliable, and the overload automatic protection can be realized. It is more and more widely used in mechanical manufacturing.

1. Hydraulic Bending Machine Work Requirements

When the bending machine is working (Figure 1), when the workpiece reaches the specified position (a2), if the start button is pressed, the cylinder extends to bend the workpiece according to the design requirements (arrival position a1), then quickly return, complete one Work cycle If the workpiece does not reach the specified position (a2), the cylinder does not operate even if the button is pressed. In addition, in order to meet the requirements of processing workpieces of different materials or diameters, the system working pressure should be adjustable.

2. Bending Force Calculation

At present, for the V-type free bending, there are generally two calculation formulas for the commonly used bending force. In the calculation formula, the width V of the mold opening is generally 8 to 10 times the thickness S of the sheet material, and the inner diameter of the bending workpiece is r = (0.16 ~ 0.17) V, as shown in Figure 2.

 F——bending force, KN;

 S——sheet thickness, mm;

 l——sheet bending length, m;

 V——lower opening width, mm;

 σb – material tensile strength, MPa.

For example, a steel plate with a length l =1m, a thickness S =2mm and a material tensile strength σb = 450MPa is taken as an example, and the bending radius r =3.5mm and the lower mold opening width V =20 mm.

First calculate the aspect ratio and aspect ratio:

  V/S = 10    r/V = 0.17

  The width-to-thickness ratio and the aspect ratio are in accordance with the formula range requirements, and the bending force is calculated by two calculation formulas:

From the calculation results, it can be seen that the bending force calculated by the two commonly used calculation formulas is not much different, and the F=416KN calculated by the previous formula is selected as the sheet bending force for design.

3. Bending Machine Pneumatic System Design

Analyze the working requirements of the bending machine. The pneumatic system of the bending machine has a lower moving speed and a small moving distance, but the required bending force is large. When returning, it saves man-hours and needs to return quickly. For the position control of the bent plate, the stroke switch can be used. Because the bending machine has a large bending force, in order to ensure safety, double pressure valve control is considered in the design of the pneumatic system. According to the analysis, the pneumatic system diagram of the bending machine is designed, as shown in Figure 3.

Bending machine pneumatic system working principle: the sheet moves to the a2 position to press the valve 9, press the valve 3, the compressed air enters the double pressure valve 4 through the valve 3 and the valve 9, enters the valve 7 left air control port, the valve 7 left position Working, the compressed air intake valve 7 is left to enter the cylinder without the rod cavity through the valve 5, and the piston is extended to bend.

When the sheet material is bent and pressed to the a1 position, the valve 8 is opened, the compressed air enters the right air control port of the valve 7 through the left position of the valve 8, and the valve 7 is changed to the right position, and the compressed air enters the cylinder with the rod chamber through the valve 7, and the rodless chamber The compressed air is discharged through the quick exhaust port of the valve 5, and the piston is quickly retracted.

4. Selection of Cylinders For Pneumatic System of Bending Machine

At present, China has produced five kinds of standardized cylinders for users to choose. In the production, try to use standardized cylinders. According to the hydraulic and pneumatic design manual, the cylinder intake pressure p=1MPa, select the cylinder load rate η=75%, calculate the cylinder inner diameter according to the cylinder bore diameter calculation formula:

According to the cylinder inner diameter standard, a cylinder having an inner diameter of 250 mm and a piston rod diameter of 70 mm is selected.

5. Conclusion

Bending machines are widely used in various industries. The bending machine adopts pneumatic system design to reduce the environmental impact caused by oil leakage, save energy and easy to use. Through the analysis of the work of the bending machine, the pneumatic system of the bending machine is designed, and the cylinders used are selected. It is expected to provide reference for the subsequent design of the pneumatic system of common mechanical equipment.