Nestable Metal Can Body Wall-Ironing Without Coating Damage
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Solution Overview
Problem
Current can manufacturing processes using wall-ironing techniques face challenges with pre-coated metal, such as limited thickness reduction, damage to polymer coatings, and difficulty in forming nestable cans with tapers or steps, due to work-hardening and frictional issues.
Innovation Solution
A method involving a two-part tooling apparatus that positions a wall-ironing punch and die to reduce thickness and increase height of the can body while avoiding the open end, and uses a punch with varying diameters to form regions with specific diameters, allowing for the creation of nestable cans with tapers and steps without damaging coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If wall-ironing is used to reduce can wall thickness, then material cost is reduced, but the polymer coating is damaged
Solution Approach 1:
The polymer coating is applied to the metal sheet before the wall-ironing process. This preliminary coating protects the metal surface during the high-friction wall-ironing operation, preventing oxidation and surface damage that would otherwise occur before the can is completed and coated afterward.
Solution Approach 2:
The process changes the physical state and properties of the metal-coating system by controlling temperature and pressure parameters during wall-ironing. By maintaining appropriate temperature ranges and pressure levels, the coating remains flexible and adherent during the forming process, preventing damage while still allowing the metal to be shaped.
2Loss of substance
If wall-ironing is used to reduce can wall thickness, then material cost is reduced, but frictional forces damage the coating
Solution Approach 1:
Temperature and pressure parameters are controlled during wall-ironing to maintain the polymer coating in a state that resists frictional damage. The heat generated during forming is managed to prevent coating degradation, while pressure is optimized to ensure coating adhesion without causing delamination or surface damage.
3Ease of manufacture
If conventional wall-ironing is used, then can body is formed, but nestable cans with tapers or steps cannot be created
Solution Approach 1:
The wall-ironing process is divided into multiple stages with different tool profiles. The wall-ironing tool includes different diameter sections that can be selectively engaged to create various wall thickness profiles, enabling the formation of tapers and steps required for nestable can configurations.
Solution Approach 2:
The wall-ironing tool is designed with movable or adjustable components that allow the ironing diameter and profile to be changed during the forming process. This dynamic capability enables the same tool to create different can geometries including straight walls, tapers, and stepped profiles for nestable designs.
4Manufacturing precision
If the wall-ironing die passes beyond the open end of the cup, then complete wall ironing is achieved, but the coating at the open end is damaged
Solution Approach 1:
The wall-ironing tool is designed with varying diameter sections where different portions of the tool engage different sections of the can wall. The tool profile is optimized so that the ironing action is concentrated on the body portion while the open end receives minimal or no ironing, preserving the coating quality at the rim where it is most vulnerable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables efficient thickness reduction and formation of nestable cans with tapers or steps, reducing material costs and avoiding coating damage, while maintaining the integrity of pre-applied polymer coatings.
Implementation Method 1
a wall-ironing die is moved axially over the closed end of the cup towards the open end of the cup, but not beyond the open end of the cup, in order to iron the cylindrical wall from the closed end up to a position axially spaced from the open end
Implementation Method 2
A method involving a two-part tooling apparatus that positions a wall-ironing punch and die to reduce thickness and increase height of the can body while avoiding the open end, and uses a punch with varying diameters to form regions with specific diameters
Data Source
Figure 1A~1D
Figure 2A~2C
Figure 3A~3C
AI summary
A metal can body (71) comprising a base (72) defining a bottommost end of the metal can body (71), a curl (115) disposed at an uppermost end of the metal can body (71), a circumferential body-wall (73) disposed between the curl (115) and the base (72), the bodywall (73) including a plurality of circumferential wall regions and a plurality of circumferential taper portions, wherein adjacent pairs of the wall regions have one of the taper portions disposed therebetween, each one of the taper portions having a taper portion upper diameter and a taper portion lower diameter, the taper portion upper diameter being greater than the taper portion lower diameter such that each one of the taper portions is downwardly tapered, and wherein the metal can body (71) is nestable with other ones of the metal can bodies (71).