In the forming process of aluminum foil lunch boxes, wrinkles are mainly related to factors such as the quality of the aluminum foil blank, forming process parameters, mold design, and lubrication conditions. To avoid wrinkles, a systematic solution needs to be built from multiple dimensions, including raw material control, process optimization, equipment adjustment, and operational specifications.
The shape quality of the aluminum foil blank is fundamental to the forming effect. If the incoming material has problems such as wavy edges, loose center, or uneven thickness, wrinkles are easily caused by local differences in elongation during stamping and stretching. For example, wavy edges will cause uneven stress on the aluminum foil during guide rollers or winding, forming transverse creases; loose center may produce longitudinal wrinkles under the action of the blank holder. Therefore, it is necessary to strictly screen the blanks to ensure that their surface is flat and the thickness is uniform, and to pre-treat the blanks before forming, such as leveling and degreasing, to eliminate potential defects.
The matching of forming process parameters is crucial for wrinkle control. Stamping speed, blank holder force, and stretching depth need to be dynamically adjusted according to the aluminum foil thickness and material characteristics. If the stamping speed is too high, the aluminum foil may break due to insufficient flow; if the speed is too slow, the material may be overstretched, forming wavy lines. Insufficient blank holder force will cause the blank to slip, while excessive force may tear the material. For example, in deep drawing processes, multiple trial runs are needed to determine the optimal blank holder force, ensuring uniform deformation of the aluminum foil during stretching and avoiding localized accumulation.
The design of the aluminum foil lunch box mold is crucial to preventing wrinkles. The corner radius of the mold and the clearance between the punch and die must be precisely controlled. A corner radius that is too small will cause excessive thinning of the aluminum foil at the bend, easily leading to cracks; uneven clearance may cause excessive pressure on one side of the aluminum foil, forming wrinkles. Molds for smooth-walled aluminum foil containers require high-precision machining to ensure the fitting clearance between the punch and die is within a reasonable range. Simultaneously, the mold surface must be polished to a mirror finish to reduce frictional resistance and prevent the aluminum foil from being scratched or wrinkled.
Lubrication conditions directly affect the frictional characteristics between the aluminum foil and the mold. Insufficient lubrication can cause the aluminum foil surface temperature to rise, softening the material and making it prone to sticking to the die during stretching, resulting in wrinkles or aluminum adhesion defects. Specialized aluminum foil forming lubricant should be used and evenly sprayed onto the blank surface to ensure comprehensive and appropriate lubrication layer coverage. Simultaneously, residual lubricant and aluminum shavings on the die surface must be cleaned regularly to prevent impurities from embedding and increasing localized friction.
The stability of the edge-pressing device plays a crucial role in controlling wrinkles. The edge-pressing ring of the aluminum foil lunch box must be kept horizontal and have uniform contact pressure with the blank. If the pressure on one side of the edge-pressing ring is too high, it will push the aluminum foil to the other side, forming a one-sided wrinkle. Pressure sensors can be installed to monitor the edge-pressing force in real time, and the pressure distribution can be automatically adjusted in conjunction with an elastic edge-pressing device. Furthermore, the gap between the edge-pressing ring and the die must be checked regularly to prevent excessive gap due to wear, which would affect the edge-pressing effect.
The skill level of the operators is also an important factor in avoiding wrinkles. Standardized operating procedures for feeding, centering, and winding are necessary. For example, when the billet enters the rolls, it must be aligned with the rolling centerline to avoid uneven stress caused by misalignment; during winding, tension must be kept stable to prevent the aluminum foil from becoming loose or tight due to tension fluctuations. Regular training to improve operators' process knowledge and equipment operation skills can effectively reduce wrinkle defects caused by human factors.
Wrinkle control in aluminum foil lunchbox forming needs to be integrated throughout the entire process, including raw materials, processes, equipment, and operations. By strictly controlling billet quality, optimizing process parameters, designing precision molds, improving lubrication conditions, stabilizing the edge-pressing device, and improving operator skills, the incidence of wrinkle defects can be systematically reduced, improving product qualification rate and forming quality.
