Metal bending spring back is a common phenomenon after a metallic material is subjected to bending forces. When a metal is bent, it undergoes elastic deformation, which means it changes its shape temporarily. However, when the external forces responsible for this deformation are removed, the metal will try to return to its original shape, resulting in a “spring back” effect.
The degree of spring back in the metal may vary depending on several factors, including the type of metal, its thickness, the degree of bending, and the bending methods used. In many cases, the spring back effect can be compensated by over-bending the metal in the opposite direction, although this technique requires careful calculations and professional skills.
8 factors affect metal bending spring back
Metal bending spring back is affected by a variety of factors, including:
- Material properties: The material properties of the metal, such as its elastic modulus, yield strength, and work hardening behavior, affect the amount of spring back. Materials with a higher elastic modulus and yield strength are more likely to experience more excellent spring back.
- Bending radius: The bending radius of the tool used to bend the metal affects the amount of spring back. Larger bending radii tend to produce less spring back compared to smaller radii.
- Bending angle: The angle of the bend also affects the spring back. Greater bending angles tend to produce more spring back than smaller angles.
- Bend direction: The direction of the bend, whether it is a single or double bend, also affects the amount of spring back. Double bends tend to produce more spring back than single bends.
- Tool design: The design of the tool used to bend the metal also affects the spring back. Tools with sharper edges tend to produce more spring back than those with smoother edges.
- Tool material: The material of the tool also affects the spring back. Softer tool materials tend to produce less spring back than harder materials.
- Lubrication: The use of lubrication during the bending process can affect the spring back. Insufficient lubrication can cause friction between the metal and the tool, leading to greater spring back.
- Annealing: The heat treatment process of annealing can reduce the amount of spring back by relieving the internal stresses in the metal.
By considering these factors, metal bending processes can be optimized to minimize spring back and produce high-quality, accurately shaped parts.
Eight main Measures to reduce spring back
- Under the condition close to pure bending, necessary corrections can be made to the shape of the working part of the bending die according to the calculation of the rebound value or empirical data.
- Utilizing the law of different spring back directions of different parts of the bent workpiece, properly adjust various influencing factors (the radius of the fillet of the mold, the gap, the width of the opening, the correction force, the pressing force, etc.), so that the spring back in opposite directions cancel each other out. As shown in Figure 1, use the spring back generated by the bottom of the part to compensate for the spring back of the two fillets
- The soft mold of polyester rubber is used instead of the rigid mold of metal for bending. as shown in Picture 2
- Make the bending punch or the binder plate into a partially protruding shape, or reduce the mold gap in the fillet part, so that the punch force can concentrate on the bending deformation area that causes spring back, and change its stress state, as shown in Figure 3 Show
- A die structure with a swing block is adopted, as shown in Figure 4.
- Using the longitudinal compression method, after the bending process is completed, the shoulder of the mold is used to pressurize the longitudinal direction of the bent hair, so that the stress on the cross-section of the hair in the bending deformation zone becomes compressive stress, as shown in Figure 5.
- The stretch bending method shown in Figure 6 is mainly used for parts with relatively large lengths and curvature radius
- The method of improving the structural rigidity of the workpiece is adopted, as shown in Figure 7 to Figure 9.
Six technical measures to reduce spring back
Springback is a common phenomenon that occurs during metal bending, where the metal tends to return to its original shape after being bent due to the elastic deformation of the material. This can be a significant issue in the manufacturing industry as it can affect the accuracy and quality of the final product.
The degree of spring back depends on various factors such as the material properties, the bending radius, the bending angle, and the tooling used for the bending operation. To minimize spring back, the following techniques can be used:
- Overbending: This technique involves bending the metal beyond the required angle and then releasing the pressure, allowing the material to spring back to the desired angle.
- Bottoming: This technique involves bending the metal until it touches the die, which helps to minimize the elastic recovery of the material.
- Pre-bending: This technique involves bending the metal slightly in the opposite direction before the final bend. This can help to compensate for the spring back during the final bend.
- Material selection: Choosing a material with a lower elastic modulus can help to reduce the amount of spring back.
- Tooling design: The design of the tooling used for the bending operation can also influence the degree of spring back. A larger bending radius can help to reduce the amount of spring back.
- Post-bending heat treatment: Heat treatment can be used to relieve the stresses in the material and reduce the amount of springback.
Combining these techniques makes it possible to minimize the degree of spring back and produce high-quality bent metal parts with the desired shape and accuracy.