Skip to content

Seven main factors affecting metal bending 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.

Springback of metal bending

Inconsistencies between part and mold dimensions due to springback
Inconsistencies between part and mold dimensions due to spring back

When the metal is bent, plastic deformation and elastic deformation exist at the same time. When the external load is removed, the elastic deformation disappears, so that the size of the workpiece is inconsistent with the size of the mold. This phenomenon is called spring back. The spring back is generally expressed by the change of the angle. When bending with a large fillet radius, in addition to the spring back angle, the change of the bending radius should also be obtained.(As shown on the right)

Seven main factors affecting rebound

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.

Factor 1#: Mechanical properties of the material

The higher the yield point of the material, the smaller the modulus of elasticity, and the more intense the work hardening, the greater the rebound.

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 greater spring back.

Factor 2#: Relative 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.

When the relative bending radius is small, the total tangential deformation on the outer surface of the curved blank is large, and although the value of elastic deformation also increases, the proportion of elastic deformation in the total deformation decreases. Therefore, spring back The ratio of the corner to bend angle, and the ratio of curvature rebound to the radius of curvature both change with decreasing bend radius

Factor 3#: Bend Angle

The angle of the bend also affects the spring back. Greater bending angles tend to produce more spring back than smaller angles.

The larger the bending angle, the larger the length of the deformation zone and the larger the spring back angle. But it does not affect the spring back of the radius of curvature.

Factor 4#: Bending method and mold structure

Different bending methods and mold structures have a greater impact on the bending process, stress conditions, and deformation and non-deformation areas of the workpiece, so the spring back values are also different.

  • 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.

Factor 5#: Bending Force

In actual production, the bending method with a certain correction component is often used, so the force given by the press exceeds the force required for bending deformation. At this time, the stress state and strain properties of the bending deformation zone are different from those of pure bending, and the greater the applied force, the more significant the difference. When the correction force is very large, it may completely change the nature of the stress state in the deformed area of the hair, and convert the non-deformed area into a malformed area.

Factor #6: Friction

The friction between the surface of the curved workpiece and the surface of the mold can change the stress state of each part of the curved workpiece, especially when the curvature of multiple parts is bent at one time, the impact of friction is more significant. It is generally believed that friction can increase the tensile stress in the bending deformation zone in most cases and can make the shape of the part close to the shape of the mold. However, the influence of friction is often unfavorable in stretch bending.

4 roll plate rolling machine rolling a cone sheet metal【sheet metal cone roller】sheet metal cone rolling

Factor 6#: Plate thickness deviation

When plate bending, if the metal plate thickness deviation of the metal sheet is significant, for a certain mold, the actual working gap is suddenly large and small, so the spring back value is also fluctuating.

The thickness of the metal plate has a significant influence on bending springback. As the thickness of the metal plate increases, the degree of springback also increases.

This is because thicker plates have higher stiffness and yield strength, which makes them less susceptible to plastic deformation and more likely to experience elastic deformation. When a thicker plate is bent, it undergoes greater elastic deformation, and this elastic deformation results in more springback.

In addition, the bending force required to bend a thicker plate is also greater than that required to bend a thinner plate. This greater force can cause greater elastic deformation, leading to more springback.

Final Words

By considering these factors, metal bending processes can be optimized to minimize spring back and produce high-quality, accurately shaped parts.