During the stamping process of car welcome pedal trim, springback is a critical issue affecting dimensional accuracy and assembly quality. Springback is essentially the release of residual elastic strain after plastic deformation, causing the part shape to deviate from the mold design. Addressing this challenge requires a multi-dimensional solution encompassing material selection, process design, mold optimization, and equipment control, forming a comprehensive process control system from source to finish.
Material properties are the foundation for springback control. While high-strength steel can improve the deformation resistance of car welcome pedal trim, its high yield strength and large elastic modulus make it more susceptible to springback. Therefore, while meeting strength requirements, materials with lower yield strength and higher elongation should be prioritized. Alternatively, annealing can be used to reduce the material's hardness and minimize its tendency to elastic recovery. For example, when using cold-rolled carbon steel, controlling the annealing temperature and time can refine the material's grain size, improve its plastic deformation capacity, and thus reduce springback.
Process design requires structural optimization to distribute stress. Complex decorative parts are prone to springback due to localized stress concentration. In such cases, a step-by-step forming process can be used to break down the overall bend into multiple, smaller-angle bends, gradually releasing internal stress. For example, U-shaped decorative parts can be pre-bent to 90° before being adjusted to the target angle through a reshaping process to avoid the accumulation of springback caused by a single, large-angle bend. Furthermore, adding reinforcing ribs or anti-springback ribs to the part edges can alter the stress distribution path and inhibit elastic recovery.
Mold design is a key component in springback control. Mold clearance directly influences material flow and stress state. Excessive clearance can easily lead to springback, while too small a clearance can cause cracking. Therefore, mold clearance must be controlled within a reasonable range based on material thickness and elastic modulus, and localized finishing can be used to ensure uniformity. For areas prone to springback, a negative clearance design can be employed: a pre-set offset on the mold working surface ensures that the part reaches the target dimension after springback. At the same time, the mold insert material must possess high hardness and wear resistance. For example, using Cr12MoV steel and quenching it to HRC58-62 can effectively reduce gap variations caused by mold wear and maintain long-term accuracy.
Equipment control and process parameter optimization are key to dynamic adjustment. Hydraulic stamping equipment, due to its stable pressure and long hold time, can better control springback. In the bending process, increasing the hold time allows the material to fully plastically deform and reduces elastic recovery. Furthermore, adjusting the blank holder force can improve material flow uniformity and avoid localized excessive stretching or compression. For example, in the drawing process, using segmented blank holder force control can apply higher pressure during the initial flow of the material into the mold to prevent wrinkling, while gradually reducing the pressure later to minimize springback.
The shaping process is the last line of defense for springback compensation. For parts that have already experienced springback, additional shaping steps can be used for secondary correction. For example, adding shaping inserts to the sidewalls of U-shaped decorative parts can apply reverse pressure to the springback area, forcing the material back into the plastic deformation zone and eliminating elastic deviation. The design of the shaping insert must precisely match the part shape and be made of high-hardness material to ensure dimensional stability.
Simulation analysis and experimental verification are key tools for closed-loop control. Simulating the stamping process with CAE software can predict springback and optimize compensation strategies, reducing mold trials. For example, in the development of a car welcome pedal trim for a certain vehicle model, simulation analysis determined the springback compensation values to be 15mm in the length direction and 7mm in the width direction. After actual verification, the springback was controlled within 2mm, meeting assembly requirements. Furthermore, a springback database was established to accumulate springback patterns for different materials, shapes, and processes, providing empirical support for subsequent projects.
Springback control for the stamping of car welcome pedal trim must be integrated throughout the entire design, manufacturing, and verification process. Through the integrated application of material optimization, process analysis, precise mold design, equipment parameter adjustment, shaping compensation, and simulation verification, part dimensional accuracy can be significantly improved, ensuring a perfect fit between the car welcome pedal trim and the vehicle body, ultimately achieving high-quality, efficient, and stable production.
