In the process of sheet metal processing, the bending machine is a key equipment, widely used in the forming processing of metal plates. When using the bending machine for bending operations, reasonably selecting the size of the lower die opening is an important factor to ensure the quality of workpiece forming, improve production efficiency, and extend the life of the mold. This article will introduce in detail the calculation methods and influencing factors of the lower die opening of the bending machine.



One, The importance of lower die opening



The lower die opening refers to the opening width of the V-shaped groove of the lower die of the bending machine. It directly affects the flow, springback, forming angle, and stress condition of the material during the bending process. If the opening is too large, it may result in insufficient sharpness of the bending angle and even failure to form; if the opening is too small, it may cause material破裂, accelerated wear of the mold, and even damage to the equipment.



Therefore, choosing the appropriate lower die opening is the foundation for achieving high-quality bending forming.



Two, Basic calculation methods of lower die opening



In most cases, the size of the lower die opening is determined by the thickness of the plate (t). One empirical formula is:



Lower die opening = plate thickness × (6~10)



This proportion range (6~10) is applicable to most low-carbon steel materials and is a summary of experience. For example, when the plate thickness is 2mm, the lower die opening should be selected between 12mm and 20mm.



However, the specific values need to be adjusted according to the following factors:



- Material type and strength: High-strength steel plates, stainless steel, and other materials have poor plasticity and require a larger opening to avoid cracking;

- Bending angle: The smaller the angle (such as acute angle bending), the smaller the required opening;

- Control of springback: For materials with large springback, appropriately reducing the opening size can help control the angle;

- Mold type and condition: There are slight differences in mold design among different manufacturers, and wear during use will also affect the actual effect.



Three, Matters needing attention in practical application



1. Refer to the manufacturer's recommended values: Most mold manufacturers will provide recommended opening values for different thicknesses and materials, which should be used as a priority;

2. Conducting trial bending test: Before actual operation, it is recommended to conduct a trial bend and adjust the opening size according to the results of the trial bend;

3. Combination with upper die radius selection: The R angle of the upper die should also match the lower die opening to ensure the quality of forming;

4. Regularly inspecting die wear: After long-term use, the lower die opening may become larger, affecting the bending accuracy, and should be replaced in time.



Four, Summary



Selecting the lower die opening reasonably is a key step to ensure the quality of bending. By mastering the basic calculation methods and adjusting them according to actual materials and process requirements, the bending efficiency and product pass rate can be effectively improved. At the same time, operators should have a certain amount of practical experience, combining trial bending and adjustment to ensure that each processing can achieve the best effect.



In summary, scientifically calculating and selecting the lower die opening in the bending process is not only helpful in improving product quality but also in extending the service life of the equipment, which is an important link that cannot be ignored in sheet metal processing.