In the high-precision stamping process of car seat parts, controlling the uniformity of sheet metal flow is crucial for ensuring forming quality and reducing defects. Uneven sheet metal flow can lead to problems such as localized thinning, cracking, and excessive springback, directly affecting the strength, rigidity, and dimensional accuracy of the seat. To achieve this goal, a comprehensive approach is needed, encompassing mold design, process parameter optimization, material selection, and simulation-assisted design.
Mold design is the primary factor in controlling sheet metal flow. The mold's surface design must be highly compatible with the sheet metal's deformation characteristics. By optimizing the shape, position, and number of draw ribs, the sheet metal is guided to flow along a predetermined path. For example, in the deep drawing area of the seat frame, a well-placed array of draw ribs can increase the flow resistance of the sheet metal, preventing excessive localized thinning; while in shallow drawing or transition areas, resistance must be reduced to prevent wrinkling. Furthermore, the uniformity of mold clearance is also critical. Inconsistent clearance will cause the sheet metal to shift due to uneven stress during flow, resulting in dimensional deviations in the formed parts. Therefore, strict control of machining accuracy is necessary during mold manufacturing to ensure that the clearances of each part meet design requirements.
Optimization of process parameters is a key means of controlling sheet metal flow. The blank holder force in car seat parts is one of the main parameters affecting sheet metal flow, directly influencing the friction between the sheet metal and the die. Insufficient blank holder force leads to excessively rapid sheet metal flow, causing localized thinning or cracking; excessive force may hinder flow, causing wrinkling or increased springback. Therefore, the optimal blank holder force must be determined through experimentation or simulation based on sheet metal thickness, material properties, and part shape. Furthermore, stamping speed and lubrication conditions also affect sheet metal flow. For example, high-speed stamping may cause uneven sheet metal flow due to inertia, while proper lubrication can reduce friction and improve flow.
Material properties have a decisive impact on the uniformity of sheet metal flow. Different materials exhibit significant differences in parameters such as yield strength, elongation, and anisotropy index, directly affecting their forming performance. For instance, high-strength steel, due to its high yield strength, has high flow resistance and is prone to cracking in deep-drawing regions; while aluminum alloys, with better elongation, flow more uniformly, but springback issues must be considered. Therefore, material selection must comprehensively consider the functional requirements of the part, forming process, and cost, prioritizing materials with excellent forming performance. Simultaneously, improving the internal structure of the material through pretreatment processes (such as annealing and deep drawing straightening) can also enhance its flow uniformity.
Simulation technology provides strong support for sheet metal flow control. Finite element analysis software can simulate the deformation behavior of sheet metal during stamping, predict areas of uneven flow and potential defects, thereby optimizing mold design or process parameters in advance. For example, simulation can reveal the flow resistance distribution at the draw bead, allowing for adjustment of draw bead parameters to improve flow uniformity; it can also simulate sheet metal flow under different blank holder forces to determine the optimal blank holder force range. The application of simulation technology significantly reduces the number of trial runs, lowers development costs, and improves process stability.
The rational design of the sheet metal shape and size is also a crucial aspect of controlling flow uniformity. If the sheet metal size is too large, wrinkles are likely to occur at the edges during forming; if the size is too small, insufficient material may prevent the part from being formed. Therefore, it is necessary to accurately calculate the sheet metal unfolded dimensions based on the part shape and forming process to ensure a balance between material utilization and forming quality. Furthermore, by pre-cutting process notches or supplementary process surfaces, the local flow resistance of the sheet metal can be adjusted, guiding the material to flow along a predetermined path and preventing cracking or wrinkling.
The contact state between the mold and the sheet metal also significantly affects flow uniformity. A contact position close to the mold center avoids uneven stress on the sheet metal due to contact misalignment; while a uniform distribution of the contact area reduces local stress concentration and lowers the risk of cracking. Therefore, the mold design must optimize the structure of the contact area to ensure uniform stress on the sheet metal during forming.
Real-time monitoring and adjustment during production is the last line of defense for ensuring uniform sheet metal flow. Online detection equipment (such as laser measuring instruments and strain sensors) can monitor parameters such as the sheet metal's flow rate and deformation in real time, promptly identifying anomalies and adjusting process parameters. For example, if excessive flow is detected in a certain area, the blank holder force in that area can be appropriately increased or lubrication conditions adjusted to suppress excessive flow.
