| Three-Piece Can Body |
Tinplate steel; electrolytic tin-coated steel is commonly used for food and general-line packaging. |
0.14–0.30 mm |
Forms the cylindrical wall and provides the main load-bearing shell of the can. |
Must resist buckling during filling, stacking, retorting, transport, and internal or external pressure changes. The body should maintain a uniform diameter, roundness, seam alignment, and adequate panel stiffness.
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Sheet temper and thickness control; accurate blanking; consistent forming diameter; controlled longitudinal seam geometry; prevention of sharp edges and coating damage.
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Thickness, coating mass, body diameter, height, roundness, seam appearance, leakage, dent resistance, and dimensional conformity.
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| Longitudinal Side Seam |
Tinplate steel joined by electric resistance welding; internal and external protection may be applied where required. |
Based on body wall thickness |
Joins the rectangular body blank into a continuous cylindrical body. |
The seam must provide continuous mechanical strength and leak-tightness without excessive weld bead, distortion, burn-through, pinholes, or local loss of corrosion protection.
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Welding current, voltage, speed, electrode condition, overlap, seam tracking, cooling, and protective coating application.
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Visual seam inspection, destructive seam tests, electrical or pressure leak testing, weld continuity, coating coverage, and corrosion-resistance checks.
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| Top End |
Tinplate steel with an internal protective lacquer selected for the packed product. |
0.18–0.30 mm |
Closes the can and provides the opening or access feature for filling, processing, and consumer use. |
Must withstand double-seaming loads, internal pressure, vacuum conditions, thermal processing, and handling. Countersink depth and curl geometry must support a secure hermetic seam.
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Accurate stamping, controlled curl and countersink dimensions, compound application, score-line control when applicable, and consistent coating coverage.
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End diameter, countersink depth, curl, compound weight, score depth, seam compatibility, pressure resistance, and coating integrity.
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| Bottom End |
Tinplate steel with internal and external protective coatings appropriate to the product and process. |
0.18–0.30 mm |
Provides the fixed base of the can and transfers stacking and handling loads through the end profile. |
Requires sufficient panel strength, controlled center-panel movement, stable countersink geometry, and resistance to buckling during retorting, vacuum formation, and pallet stacking.
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Stamping depth, bead or profile formation, curl accuracy, compound application, flatness, and control of local thinning around formed features.
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Panel height, countersink depth, end profile, axial load, pressure or vacuum resistance, seam performance, and leakage.
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| End Curl |
Formed tinplate edge at the perimeter of the top or bottom end. |
Typically 1.5–3.0 mm radial curl width |
Creates the interlocking metal geometry used in the double seam between the end and the body flange. |
Must be continuous, smooth, and dimensionally stable. Inconsistent curl can cause seam looseness, false seams, droops, wrinkles, or loss of hermetic integrity.
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Curl diameter, curl height, edge condition, die alignment, press setup, and prevention of cracks or exposed steel.
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Curl dimensions, visual defects, cross-section inspection, seam teardown, and evidence of coating or lacquer damage.
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| Body Flange |
Flanged tinplate steel formed at one or both ends of the can body. |
Based on body wall thickness |
Provides the body-side portion of the double-seam joint with the can end. |
Must have a uniform flange width and smooth transition from the sidewall. The flange must not contain cracks, excessive wrinkles, sharp projections, or deformation that could compromise seaming.
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Flanging height and width, body roundness, tool alignment, flange edge condition, and control of metal work-hardening.
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Flange width, flange angle, roundness, visual condition, seam cross-section, and leakage after seaming.
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| Double Seam |
Mechanical interlock of the tinplate body flange and end curl, usually with sealing compound. |
Geometry-dependent; commonly checked by seam measurements rather than nominal thickness |
Creates the hermetic closure that protects the contents from leakage and external contamination. |
Must provide adequate overlap, tightness, seam thickness, and body-hook and cover-hook formation. The seam should avoid cutovers, droops, false seams, excessive wrinkles, and open seams.
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Seaming-roll profile, chuck diameter, first- and second-operation settings, end compound, machine alignment, and process speed.
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Seam thickness, seam width, overlap, body-hook length, cover-hook length, tightness rating, teardown profile, and leak testing.
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| Beaded or Ribbed Sidewall |
Tinplate steel formed with circumferential beads or reinforcing ribs. |
0.14–0.25 mm |
Improves radial stiffness and helps the body resist paneling, buckling, and external handling loads. |
Beads must be evenly spaced, continuous, and free from splits or severe thinning. The profile should increase stiffness without obstructing labeling, filling, or product handling.
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Bead pitch, depth, symmetry, forming pressure, tool wear, and control of surface scoring or coating damage.
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Bead dimensions, body diameter, axial compression, vacuum resistance, visual appearance, and coating integrity.
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| Necked-In Body Section |
Tinplate steel body formed to a reduced diameter near one or both ends. |
0.14–0.30 mm |
Reduces end diameter, improves stacking efficiency, and may support compatible end or closure dimensions. |
Requires gradual transitions, consistent concentricity, adequate resistance to buckling, and sufficient clearance for end loading and double seaming.
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Necking sequence, reduction ratio, tooling alignment, lubrication, transition radius, and control of local wrinkling.
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Neck diameter, concentricity, height, transition profile, end fit, axial load, and leakage after seaming.
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| Internal Protective Lacquer |
Food-contact or general-purpose polymer coating selected according to product chemistry and processing conditions. |
Typically 3–12 g/m² dry film weight, formulation-dependent |
Separates the packaged product from the metal substrate and helps reduce corrosion, staining, and product interaction. |
Must provide continuous coverage, strong adhesion, adequate flexibility after forming, resistance to the product, and stability under pasteurization or retort conditions when applicable.
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Surface cleaning, coating weight, curing temperature and time, film continuity, adhesion, and compatibility with forming and seaming operations.
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Dry-film weight, pinhole detection, adhesion, sterilization resistance, chemical resistance, odor or taste transfer, and visual coverage.
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| External Protective Coating |
Tinplate with varnish, lacquer, or decorative coating selected for handling and environmental exposure. |
Formulation-dependent |
Protects the external surface from abrasion, moisture, staining, and corrosion while supporting printing or labeling. |
Must remain adherent after forming, seaming, washing, pasteurization, and transport. Coating should not interfere with seam formation or closure performance.
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Surface preparation, coating uniformity, curing, print adhesion where applicable, friction control, and protection of cut or welded areas.
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Visual appearance, dry-film weight, adhesion, scuff resistance, corrosion resistance, color consistency, and compatibility with labels or inks.
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| Score Line or Easy-Open Panel |
Mechanically scored tinplate end with a compatible opening feature. |
End thickness commonly 0.18–0.25 mm; score depth is process-specific |
Defines a controlled opening path while preserving closure integrity before use. |
Score depth must balance opening force and pressure safety. The residual metal must be continuous enough to prevent premature rupture during filling, processing, transport, and storage.
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Score depth, score continuity, tooling wear, residual thickness, tab or opening-feature alignment, and protection against corrosion at the score.
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Opening force, burst or pressure resistance, score depth, visual continuity, leakage, panel deformation, and consumer-edge safety.
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