In the metal stamping industry, aluminum sheet is widely used due to its light weight, high strength, and corrosion resistance. However, springback often affects product precision. The following comprehensive explanation of the key points for aluminum sheet stamping springback control focuses on springback causes, control methods, and detailed parameters to help resolve production challenges and improve product quality.

Causes of Aluminum Sheet Stamping Springback

Material Characteristics

Aluminum sheet has a certain elastic modulus. During the stamping process, the sheet undergoes plastic deformation due to external forces. When the force is removed, the elastic deformation partially recovers, resulting in springback. The elastic modulus varies between different types of aluminum sheet. For example, the elastic modulus of 6061 aluminum sheet is approximately 69 GPa, that of 5052 aluminum sheet is approximately 70 GPa, and that of 7075 aluminum sheet is approximately 71 GPa. The lower the elastic modulus, the more pronounced the springback under the same stamping conditions. The yield strength of the aluminum sheet also affects springback. For example, the yield strength of 6061-T6 aluminum sheet is approximately 276MPa, that of 5052-H32 aluminum sheet is approximately 193MPa, and that of 7075-T6 aluminum sheet is approximately 503MPa. The lower the yield strength, the higher the risk of springback.

Stamping Process Factors

1. Stamping Speed: An unreasonable stamping speed, either too fast or too slow, will affect the uniformity of aluminum sheet deformation. A speed exceeding 200mm/s can easily lead to localized stress concentration, exacerbating springback after the external force is removed, potentially increasing the springback by 5%-10%. A speed exceeding 200mm/s can cause excessive sheet deformation during the stamping process, increasing the risk of springback.

2. Stamping Gap: A stamping gap that is too large or too small can exacerbate springback issues. If the gap is too large, the aluminum sheet is prone to excessive bending deformation during the stamping process, increasing springback. If the gap is too small, the die's squeezing force on the aluminum sheet is too strong, also causing springback. Furthermore, different hardness aluminum sheets have different gap requirements: higher-hardness aluminum sheets require smaller gaps, while more ductile aluminum sheets can have larger gaps.

Mold Design Factors

Corner Radius Design Issues: Improper corner radius of the die's male and female dies. A corner radius that is too small will result in severe stress concentration at the bend during stamping, leading to significant springback. A corner radius that is too large will result in poor fit between the sheet and the die, also causing springback.

Mold Structure Design Issues: Inadequate mold structure design, such as the lack of an effective press device, can cause the aluminum sheet to move during stamping, resulting in uneven deformation and springback. Furthermore, if springback is not accounted for during the mold design phase, the stamped product will deviate from the designed dimensions due to springback.

Controlling Springback During Aluminum Stamping

Material Selection

Select the appropriate aluminum sheet type based on product requirements. Preferable aluminum sheet with a high yield strength and a large elastic modulus, such as 7075 aluminum sheet, is preferred. Its high yield strength makes it relatively more stable during the stamping process, thus reducing springback.

Material Pretreatment

Pretreatment of the aluminum sheet, such as annealing, reduces internal stress and improves its plasticity, making it easier and more uniform to deform during the stamping process, thereby reducing springback. The annealing temperature is generally controlled between 300 and 400°C, and the holding time depends on the thickness of the sheet, typically 1 to 3 hours.

Stamping Process Optimization

Rationally adjust the stamping speed. For conventional aluminum sheet stamping, maintain a speed of 50-200mm/s. For thin aluminum sheet (thickness <1mm), a speed of 50-100mm/s is recommended, while for thick aluminum sheet (thickness ≥1mm), a speed of 100-200mm/s is recommended. For complex parts (such as multi-bend aluminum sheet brackets), the speed can be appropriately reduced to 80-150mm/s to reduce springback deviation caused by stress concentration.

Precisely control the stamping gap, adjusting it based on the aluminum sheet thickness and material. For aluminum sheet with higher hardness (such as 7075 T6), the stamping gap can be set at the lower limit (1.05-1.1 times the aluminum sheet thickness); for aluminum sheet with higher plasticity (such as 5052 H32), the gap can be set at the upper limit (1.1-1.2 times the aluminum sheet thickness). This ensures a stable stamping process and reduces the risk of springback. Mold Design Improvements

Optimize the corner radius of the male and female dies. Typically, the radius should be set to 5-10 times the thickness of the aluminum sheet. For 1mm thick 6061 aluminum sheet, the radius can be designed to be 5-10mm; for 2.5mm thick 5052 aluminum sheet, the radius can be designed to be 12.5-25mm. This reduces stress concentration at the bend and reduces springback.

Add an effective hold-down device, such as an elastic hold-down plate. By adjusting the hold-down force, the aluminum sheet can be tightly adhered to the die during the stamping process, preventing movement and achieving more uniform deformation. The hold-down force should be determined based on the sheet area and material, and is generally controlled between 5-20kN.

Springback Design: Springback is a control method that predicts the springback trend and amount of aluminum sheet metal after stamping during the mold design phase and then adjusts the mold cavity or punch shape accordingly, ensuring that the aluminum sheet metal springs back exactly to the designed dimensions. This method is particularly suitable for aluminum sheet stampings with complex shapes.

Heat Treatment Correction

Heat treatment correction involves heating the stamped part to a certain temperature, holding it for a period of time, and then slowly cooling it to eliminate internal stress and reduce springback. For example, 6061 aluminum sheet can be heated to 120-180°C for 1-2 hours; 5052 aluminum sheet can be heated to 100-150°C for 1.5-2.5 hours.

As an experienced custom metal parts manufacturer, Kailai Machinery has unique expertise in addressing springback issues in aluminum stamping products. If you have such needs, please contact us and we will provide you with a one-on-one professional sol