Aluminum LIDS compatibility is established through dimensional tolerances, sealing techniques and material strength. According to the ISO 90 series standards, the standard can body diameter tolerance is ±0.1mm (typical value 66.0-66.2mm), while the aluminum can lid inner diameter must be controlled between 65.9-66.1mm to ensure that the two are compatible. Experiments conducted by the Can Manufacturers Institute in 2023 revealed that when the deviation of lid diameter was greater than ±0.15mm, the sealing failure rate would increase to 3.2% (the industrial allowable value ≤0.5%). Take the 202 standard tank of Ball Corporation as a reference. The winding tension of the corresponding aluminum cap should be maintained at a stable 35-45kN/m² or else it is not hard to make the leakage rate go from 0.01% to 1.5%.
The structural difference in the seal plays a very important role in compatibility: Double seam process requires the error in material thickness of the lid-to-can body contact area to be ≤0.02mm, and the depth of scratch on the full aperture aluminum can lid to be accurate to 0.08±0.01mm. As indicated by the actual measuring data of Daiwa Can-making in Japan, if the deviation of scratch depth is greater than 0.03mm, the range of opening force fluctuations will be as high as ±30% (the standard demanded is ±15%), which can cause the rate of consumer complaints to rise by 22%. The EU EN 13027 standard stipulates that the coating thickness of sealant on aluminum can lid should be within the range 5-8μm. Un-even thickness will decrease the air tightness, and the likelihood of high CO₂ leakage rate in carbonated beverages is four times greater.
Material strength parameters have a direct effect on compatibility: The yield strength of the aluminum cap should be ≥180MPa (thickness 0.20-0.25mm). If the variation between the tank material strength (nominal value 3104 aluminum alloy, strength 280MPa) and the cap is more than 25%, vibration in transportation will cause the probability of fatigue cracks at the sealing zone to increase from 0.1% to 2.3%. According to statistics from the China Food Packaging Association, in 2022, 12,000 bursting of LIDS of aluminum cans due to the disparity of strength between cans and LIDS and direct losses of more than 86 million yuan occurred.
Differential design is promoted by design protection law: With the EU Single-Use Plastics Directive, aluminum can LIDS must be permanently attached to the can body (anti-litter design) so that their market share decreased from 78% in 2020 to 35% in 2023. When launching the “one-piece cap” in Germany, Anheuser-Busch InBev experienced the increased cost of fine-tuning the production line increase by 12% but achieved a consumer recycling rate of 92% compared to the 68% for traditional caps. This new design has stricter demands on the tank body edge rolling accuracy. When the tank mouth flange height deviation is more than ±0.05mm (standard 1.95-2.05mm), the integral cover breaking force will vary by ±18%.
It can be seen from economic analysis that the procurement price of non-standard aluminum can LIDS is 15-30% higher than that of standard LIDS. The case of the Brazilian Coca-Cola plant shows that by applying tailor-made diameter (67.5mm) aluminium caps, the filling line speed fell from 2,000 cans per minute to 1,700 cans per minute and the annual productivity capacity loss equated to 120 million cans. The ISO 90 standard-compatible universal aluminum can LIDS can reduce the production line conversion time from 45 minutes to 8 minutes and increase the equipment utilization rate by 19%.
Technological progress is overcoming the barrier of compatibility: The smart adaptive aluminum cap, designed by Crown Holdings, dynamically adjusts sealing pressure in real time by laser detection (±1.2kN/m² accuracy), and it is possible to achieve a 100% rate of qualification in sealing within the tolerance range of ±0.2mm of the tank body. Orekin’s nano-coating technology has raised the defect tolerance of aluminum can LIDS by 50% and yet retains a leakage rate of 0.02% when the ellipticity deviation of the tank body is 0.3mm. These technologies will redefine the boundaries of compatibility between tank bodies and aluminum caps.