Springback is a critical issue affecting dimensional accuracy and assembly quality during the stamping of 304 stainless steel small gaskets. Due to the high yield strength and elastic modulus of 304 stainless steel, it exhibits a significant tendency for elastic recovery after unloading, leading to deviations between the part shape and the die surface. Optimizing die design requires a comprehensive approach considering material properties, process parameters, die structure, and compensation techniques to achieve precise control of springback.
Die clearance is one of the core factors influencing springback. Excessive clearance reduces material flow resistance, increases the elastic recovery space, and consequently increases springback; insufficient clearance may result in excessive material thinning or even cracking. For 304 stainless steel small gaskets, the punch-die clearance needs to be optimized based on the material thickness and elongation, typically controlled at 90%-95% of the material thickness on one side. For example, for a 0.2mm thick gasket, the clearance can be set to 0.18-0.19mm to ensure sufficient material flow during forming while avoiding excessive springback. Simultaneously, the die cutting edge must be kept sharp to prevent wear-induced clearance changes, which could further exacerbate springback.
In mold structure design, the introduction of a shaping process can significantly improve springback. For complex-shaped gaskets, such as those with irregular holes or local protrusions, a shaping process can be added after molding. This involves secondary pressure to induce plastic deformation in the material, offsetting some of the elastic recovery. For example, in U-shaped gasket molding, shaping inserts can be added to the mold. These inserts, made of Cr12MoV hardened to HRC58-62, apply continuous pressure to the sidewalls, causing the springback tendencies of the inner and outer layers of the material to cancel each other out. Furthermore, the shaping process needs to be integrated with pre-forming design, breaking down the one-time molding into a multi-step, progressive process to gradually release internal stress and reduce the final springback.
The radius of the fillet in the working part of the mold has a significant impact on springback. A smaller fillet radius increases stress concentration during material bending, leading to accelerated elastic recovery; a larger fillet radius may result in insufficient material flow, affecting molding accuracy. For 304 stainless steel small gaskets, the fillet design needs to be optimized according to the part shape: for right-angle bends, the fillet radius can be 1-1.5 times the material thickness; for arc transition areas, the optimal radius needs to be determined through CAE simulation analysis to avoid springback caused by excessively large or small fillets. For example, in a 90° bend of a 0.5mm thick gasket, a fillet radius of 0.5-0.75mm can effectively balance formability and springback control.
The mold material and heat treatment process directly affect its rigidity and wear resistance, thus affecting the springback control effect. For 304 stainless steel small gasket molds, the punch and die materials should preferably be high-toughness, high-hardness tool steels, such as SKD11 or ASP-23, and vacuum quenching should be used to ensure uniform hardness. For surface treatment, TD (Thermal Diffusion Carbide Coating) ultra-hardening technology can be used to form a vanadium and niobium metal carbide layer with a thickness of 5-15μm on the mold surface, increasing the surface hardness to above HV2800. This significantly reduces gap changes caused by mold wear, thereby stabilizing springback control. Furthermore, the mold surface must be kept smooth to avoid uneven material flow resistance caused by excessive roughness, which could exacerbate localized springback.
Negative springback compensation technology is an advanced strategy in mold design. By pre-setting reverse deformation in the mold surface, it offsets the elastic recovery of the material after unloading. For example, in the design of a U-shaped gasket mold, based on CAE simulation results, the mold sidewall can be pre-formed into an outward convex shape, with the convex amount set to 0.05-0.1mm according to the material springback rate. When the material springs back after forming, the outward expansion trend of the sidewall cancels out the pre-set convex amount, ultimately ensuring that the part dimensions meet the design requirements. Negative springback compensation requires precise calculations based on material properties, part shape, and process parameters to avoid new dimensional deviations caused by over- or under-compensation.
Process optimization during the mold debugging stage is the final guarantee for reducing springback. During mold trials, parameters such as blank holder force, lubrication conditions, and forming speed need to be adjusted multiple times to observe the springback variation. For example, appropriately increasing the blank holder force can allow for more complete material flow, reducing elastic recovery after unloading; optimizing lubrication conditions can reduce frictional resistance between the material and the mold, preventing springback caused by localized stress concentration. Furthermore, a comprehensive inspection of the molded samples is necessary, including dimensions, shape, and surface quality. Based on the inspection results, the mold profile or process parameters are corrected in reverse, forming a closed-loop optimization process of "simulation-mold trial-correction."
In the stamping of 304 stainless steel small gaskets, mold optimization needs to be integrated throughout the entire process of design, manufacturing, and debugging. By reasonably controlling the mold clearance, optimizing the fillet radius, introducing a forming process, using high-rigidity mold materials, applying negative springback compensation technology, and refining the debugging process, springback can be significantly reduced, improving part dimensional accuracy and assembly stability. These measures need to be combined with CAE simulation analysis and actual production experience to form a systematic springback control scheme to meet the needs of high-precision gasket manufacturing.
