1.What are the key factors affecting rebound?
Material Properties (Most Critical)
Yield Strength: This is the most important factor. The higher the yield strength, the greater the springback.
Galvanized Coil Grade: Different grades of substrate (such as DX51D, DX52D, DC01, SGCC, etc.) have different yield strengths. For example, high-strength steels such as SGC400/440/550 used for structural components have a much greater springback than ordinary DC01 (SPCC).
Zinc Coating Type and Thickness: Hot-dip galvanized (GI) and electro-galvanized (EG) substrates are different. Generally, hot-dip galvanized substrates are softer, resulting in relatively less springback. The zinc coating itself is very soft and has little impact on springback, but a thick zinc coating may produce tiny cracks at the bending point, indirectly affecting the springback.
Material Thickness (T)
The thicker the sheet, the smaller the springback. This is because when a thick sheet is bent, the compression and tensile deformation areas on both sides of the neutral layer are larger, resulting in more complete plastic deformation and a smaller proportion of elastic recovery.
2.How do you estimate rebound based on rules of thumb and reference values?
Under the most common conditions (such as low-carbon steel galvanized sheet DC01/SPCC with a thickness T=1.0-2.0mm, a bending radius R=0.5T~1T, using a standard V-groove), when bent at 90 degrees, the springback angle is approximately between 1° and 3°.
However, for high-strength steel, this value can easily reach 5°~10° or even greater.
3.How to estimate springback during trial molding and compensation?
This is the standard production process. The process engineer first sets a bending program based on experience and bends a sample.
Then, they measure the actual angle using an angle gauge and calculate the springback (for example, if the target is 90° and the actual angle is 92°, the springback is 2°).
Subsequently, they input a compensation value into the CNC bending machine, for example, requiring the machine to bend to 88° to compensate for the 2° springback, thus obtaining a 90° part.
4.How to reduce rebound?
Design Phase: Use the smallest possible bending radius, within structural limits.
Material Selection: Prioritize materials with low yield strength (e.g., DC01/SPCC instead of SGC440) while meeting strength requirements.
Bending Process:
Use a smaller lower die V-groove width.
Employ the correction method (precision pressing): At the end of the bending stroke, apply extremely high pressure to the tip of the bending angle with a small compression, causing complete plastic deformation of the material in that area, significantly reducing springback. This requires sufficient force from the bending machine.
Adjust Bending Speed: Sometimes, low-speed bending is beneficial for sufficient plastic deformation of the material.
5.How do I use a bending factor table or software?
Professional CAD/CAM software (such as SolidWorks and Pro/E's sheet metal module) includes built-in bending factor tables based on material and thickness, which already account for springback.
Some advanced CNC bending machines have adaptive control systems that can adjust pressure in real time to control springback.