Luxury Caviar Tin Box is a high-end sealed metal packaging customized exclusively for premium raw seafood and low-temperature refrigerated caviar, suitable for high-end supermarket counters, Michelin restaurant gifts, luxury fresh food gift boxes and cross-border premium seafood packaging. As extremely delicate low-temperature raw fresh ingredients, caviar has far stricter requirements for packaging tightness, edge smoothness, box flatness and low-temperature structural stability than ordinary food tin boxes. Refined multi-layer hemming process and full-edge standardized angle control are two core process barriers that distinguish this high-end tin box from ordinary food tin boxes. Most affordable seafood tin boxes on the market suffer from common defects such as wrinkled hems, sharp edges, uneven hemming angles, large box mouth gaps and hem cracking in low-temperature environments. These defects will not only scratch hands, but also damage the overall sealing effect, causing caviar to oxidize, deteriorate and absorb peculiar smells after contacting air. Starting from the exclusive packaging demands of high-end caviar, this article elaborates on the complete food-grade hemming process of Luxury Caviar Tin Box, as well as the precise angle control standards for four key positions including box mouth, lid, four corners and bottom sealing. It also analyzes the direct influence of hemming angle deviation on sealing performance, appearance texture and low-temperature durability, highlighting the sophisticated craftsmanship advantages of high-end seafood metal packaging.

　　Targeting four major usage pain points of caviar packaging: low-temperature refrigeration, sterile contact, long-term fresh keeping and high-end display, Luxury Caviar Tin Box adopts top-tier three-pass progressive double hemming process for food industry instead of the single-layer simple hemming process used by ordinary tin boxes. It features burr-free, crack-free and exposed-metal-free edges, fully complying with food safety standards for direct contact with raw food materials. The complete hemming procedure is divided into three independent processes: pre-bending forming, progressive inward hemming and compaction edge sealing. Different from the one-time rapid hemming of ordinary tin boxes, multi-pass slow-pressure hemming releases internal stress of tinplate, avoiding hem cracking and enlarged gaps caused by metal thermal expansion and contraction in low-temperature refrigeration environment. The first step is pre-bending: preliminary bending treatment is conducted on sharp exposed metal edges to eliminate sharp cuts and reserve standard deformation space for subsequent inward hemming, preventing plate fracture caused by direct thick hemming. The second step is progressive double inward hemming: special circular hemming rollers are adopted to wrap plate edges inward twice slowly to form a double-layer tightly fitted closed hem, blocking air and moisture from entering the box. The third step is leveling compaction: the formed hem is compacted horizontally to ensure uniform width and consistent radian of the whole hem, presenting smooth and streamlined appearance and matching the minimalist and premium aesthetic of high-end gift boxes. Meanwhile, synchronous hemming is processed on lid edges, box body edges and bottom sealing edges to realize full-box sharp-corner-free design, balancing edible safety and high-end gift box texture.

　　The appearance, sealing performance and structural strength of hems entirely depend on precisely fixed hemming angles in each process. Tiny angle deviation will lead to irreversible problems such as hem wrinkles, delamination, uneven width and sealing failure. Combined with the cylindrical structure of round caviar tin cans, we set exclusive constant hemming angles for four core parts with all angle parameters locked by numerical control molds to eliminate manual debugging errors, fully adapting to low-temperature storage working conditions. Firstly, main box mouth hemming angle: adopt a 162° progressive inward hemming angle. Unlike the 180° flat right-angle hemming of ordinary canned tin boxes, the large-radian inclined inward angle enables complete fitting of double-layer tinplate plates without interlayer gaps. It enhances the sealing tightness of box mouth to match the built-in silicone sealing gasket, and delivers smooth and mild edge touch to avoid finger cuts during lid opening. Besides, the 162° slow-release bending angle offsets plate rebound stress, maintaining original hem shape without rebound warping after long-term refrigeration at 0-4℃. Secondly, lid fastening hemming angle: the inner buckle hemming of the lid adopts a 24° convergent fastening angle, which fits accurately with the radian of box mouth hem. After closing, gaps around the lid are uniform without uneven tightness, further blocking air backflow and extending the fresh-keeping period of caviar. Thirdly, cylinder corner transition hemming angle: the connecting round corners of the cylindrical body adopt a48° arc transition hemming angle, enabling natural connection between straight box body and arc corners. The whole hem is coherent without breakpoints, avoiding hem accumulation and wrinkles at corners and upgrading the overall rounded premium visual texture of gift boxes. Fourthly, bottom sealing hemming angle: the double-layer bottom sealing hem adopts a 12° sunken compaction angle. The sunken hem lifts the can bottom to prevent direct contact with accumulated water in refrigerators and avoid bottom rusting. It also strengthens the bottom bearing structure, preventing bottom hem deformation under pressure during stacked display of gift boxes.

　　To meet strict standards of high-end luxury packaging, we tighten the overall hemming angle error of Luxury Caviar Tin Box. The error of all hemming angles is strictly controlled within ±0.05°, far better than the general tolerance of ±0.3° for high-end food tin boxes in the industry. Considering the low-temperature deformation characteristics of tinplate, angle rebound compensation is preset during production. Corresponding hemming angle parameters are fine-tuned in advance targeting metal shrinkage deformation in refrigerated environment, ensuring unchanged hem shape from normal-temperature delivery to low-temperature warehousing. A special full-inspection station for hemming is equipped on the production line. Optical image detectors are used to detect hem radian, angle consistency and surface flatness circle by circle, and manual re-inspection is carried out for surface smoothness. All defective products with micro wrinkles, angle deviation and uneven hem width are screened out thoroughly.

　　Equipped with top-tier three-pass double hemming process and micron-level full-point hemming angle control, Luxury Caviar Tin Box integrates food safety, ultimate sealing and fresh-keeping performance, high-end display texture and low-temperature environmental stability. It perfectly meets the packaging requirements of delicate high-end raw fresh ingredients such as caviar. Custom premium surface processes including matte frosted treatment, hot stamping embossing, exclusive laser logo engraving and customized textures are available. With minimalist and luxurious overall design, it is suitable for high-end gift sales and counter display, ranking as the preferred metal packaging for global high-end seafood and fresh food gift boxes.