Methods to Overcome Springback in Bending
After material forming, springback generally occurs. However, the amount of springback is closely related to the forming structure, die closing height, and material, making it difficult to determine precisely. Therefore, when compensating for springback, it is advisable to add an extra 1 to 2 degrees. This way, even if the bend turns out slightly larger, it is easier to adjust back. If the angle is too small, it may need to be corrected to the desired angle. Springback is typically set between 2 to 5 degrees, with different angles chosen under various circumstances:
1. When compensating for springback, use the inner bending edge as a reference point and rotate by the designated springback angle.
2. Common springback references: For bending angles α < 10 degrees, typically add 4-5 degrees of springback; for α ≥ 10 degrees, usually add 2-3 degrees of springback. Soft materials have less springback, such as brass, SPCC, while hard materials like stainless steel have more.
3. For forming a 90-degree angle, bending at a negative 90 degrees should result in a 90-degree bend.
4. For two or more consecutive bends, if high precision is required, add springback for the first bend but not for subsequent bends. Most bending machines have automatic springback compensation features that can be referenced.
When designing bending dies with internal radii, it is common to adjust the radius of the bending punch R either by not adding springback based on the original product's internal radius or by directly reducing it by a certain factor. For example, if the internal radius of the product is 1 and the material is relatively hard, the punch radius could be set at 0.8. If the material is softer, the punch radius could be set at 0.9.
If there are deviations, make several adjustments to the dies until within the tolerance range based on experience. Designing a product with a material thickness of 0.5 and an internal radius of 200mm using this method may make it challenging to determine the springback accurately. Here is a general springback formula that can be used by substituting the appropriate values.
Refer to the table below for value A.
If the required material is not listed above, refer to the table below to find the material's elastic modulus and yield strength, then calculate the springback using the formula provided.
It is advisable to create a database of commonly used materials. If certain physical parameters are missing, they can be obtained from suppliers. With correct parameters for elastic modulus and yield strength, springback in bending operations for components like spring terminals, appearance parts, and profiles can be predicted accurately.
