Aluminum Can Quality Inspection Checklist

1. Dimensional Inspection

Precision dimensions are essential to prevent filling-line jams and ensure hermetic double-seaming on high-speed lines (1,000+ cpm). Every aluminum can supplier should provide certified CMM or gauge reports matching these parameters.

• Finished Can Height: Measure overall height to tolerance limits (e.g., ±0.20 mm).
• Flange Width & Angle: Check the flange width around the neck to guarantee sufficient metal for proper double-seam formation.
• Neck & Body Diameter: Verify outer body diameter and neck diameter against mechanical drawings.
• Wall Thickness: Measure top-wall, mid-wall, and bottom-wall thickness using a pointed anvil micrometer or ultrasonic gauge.
• Dome Depth: Check bottom dome depth to ensure proper stacking and pressure resistance.
• Ovality / Out-of-Roundness: Inspect top-opening symmetry for smooth entry into filling and seaming chucks.

2. Visual & Cosmetic Defect Inspection

Visual checks can be performed manually or via 360° automated vision inspection systems. Reputable aluminum can factories reject any lot with visible defects that affect brand integrity or line performance.

• Body Dents & Creases: Check for sidewall dents, crushes, or ripples that compromise structural integrity.
• Flange Damage: Verify that top flanges are free from dings, cuts, or ovality distortion.
• Print & Decor Quality: Inspect 360° graphic printing for color accuracy, registration alignment, bleed, and ghosting.
• External Varnish / Overvarnish (OV): Check for uniform clear coat coverage without pinholes, scratches, or missing varnish.
• Foreign Contamination: Ensure empty cans are inverted, clean, and free from aluminum dust, oil, grease, or debris.

3. Structural Mechanics & Physical Strength Testing

Physical testing ensures aluminum beverage cans withstand counter-pressure filling, carbonation build-up, and multi-tier stacking during FCL ocean freight.

• Axial Load (Column Strength): Test top-to-bottom compression resistance to ensure the can withstands seaming load forces and multi-tier pallet stacking.
• Dome Buckle Strength: Pressure-test the bottom dome to determine the exact PSI at which the dome flips out (buckles) under internal beverage pressure.
• Drop / Impact Resistance: Perform controlled drop tests to verify bottom dome and sidewall resilience.

4. Internal Coating & Chemical Compliance

The internal liner (Epoxy-Phenolic or BPA-NI) protects the beverage from reacting with raw aluminum. This is a critical requirement for any food-grade aluminum can company exporting to the US, EU, or other regulated markets.

• Internal Coating Continuity (Enamel Rater / Current Test): Measure electrical conductivity in mA across an electrolyte-filled can. A low reading confirms zero micro-cracks or bare aluminum exposure.
• Coating Weight / Film Thickness: Verify dry film weight (mg/can) to ensure adequate liner barrier protection.
• Cross-Hatch Adhesion Test: Perform tape adhesion testing on the internal lacquer to ensure paint does not peel off.
• BPA / Heavy Metal Migration Compliance: Verify valid SGS / Intertek migration test reports for FDA 21 CFR or EU 1935/2004 compliance.

5. End / Lid (EOE) & Double Seam Inspection

Double seam integrity is the ultimate line defense against product leaks, spoilage, and micro-contamination when applying 202 SOT, CDL, or B64 easy open ends.

Easy Open End (EOE) Checks

• Pop & Push Force: Test the exact pull-tab activation force required to open the lid (ensuring it is neither too stiff for consumers nor loose enough to leak).
• Lining Compound Weight: Check the dry compound gasket weight around the rim of the lid to ensure a tight vacuum seal.

Seam Teardown & Inspection (Post-Seaming)

• Seam Height (Length/Width): Measure total vertical height of the finished double seam.
• Seam Thickness: Measure maximum horizontal thickness across the seamed metal layers.
• Countersink Depth: Check distance from top of seam to end panel adjacent to seam wall.
• Body Hook & Cover Hook Overlap: Perform destructive teardown cross-sectioning to verify mechanical interlocking percentage between body flange and lid curl.
• Tightness Rating / Wrinkle Test: Inspect cover hook after teardown for smooth metal folding without excessive wrinkles.

6. Quality AQL Severity Scale

Frequently Asked Questions