Selective Can End Shell Thinning Without Wrinkling
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Solution Overview
Problem
The can making industry faces challenges in reducing the amount of metal used while maintaining strength, as thinner gauges tend to wrinkle and limit space for scorelines and pull tabs, and existing solutions either sacrifice material thickness or result in uneven thinning.
Innovation Solution
A selectively formed shell with a center panel, circumferential chuck wall, and annular countersink, where specific portions are stretched and thinned, and tooling with a force concentrating forming surface and hybrid bias generating assembly to achieve uniform thinning without excessive loading on the press.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the gauge of stock material is reduced to decrease material usage, then material consumption is reduced, but the can end tends to wrinkle during forming
Solution Approach 1:
The patent applies local quality by selectively thinning only specific portions of the can end shell (such as the curl and flange areas) while maintaining the original gauge in critical areas like the center panel and chuck wall. This localized thinning approach reduces overall material consumption while preserving the structural integrity and wrinkle resistance of areas subjected to high forming stresses.
Solution Approach 2:
The shell is divided into multiple zones with different thickness requirements. The forming process is segmented to apply differential stretching - aggressive thinning in non-critical areas and minimal deformation in critical areas. This segmentation allows material reduction without compromising overall forming quality.
2Loss of substance
If the blank size is reduced to decrease material usage, then material consumption is reduced, but the area of the end panel is sacrificed
Solution Approach 1:
The patent maintains the full blank size to preserve end panel area, then applies local quality by selectively removing material only from specific portions (curl, flange, and other non-critical areas) through controlled stretching. This ensures sufficient end panel area for scorelines and pull tabs while still achieving material reduction through localized thinning.
3Loss of substance
If conventional forming is used to thin the shell uniformly, then material usage is reduced, but excessive loading is applied to the press
Solution Approach 1:
The patent applies local quality in the forming process by using a force concentrating forming surface that directs high pressure only to specific areas requiring thinning (such as the curl and flange regions) while applying minimal or no pressure to areas that already have sufficient thickness. This localized force application achieves the desired thinning pattern without requiring excessive overall press loading.
Solution Approach 2:
The forming process is segmented into multiple stages with different pressure applications. The force concentrating surface divides the forming action into localized zones, allowing material to be removed from specific areas without subjecting the entire shell to high forces that would overload the press.
4Loss of substance
If conventional forming is used to thin the shell, then material usage is reduced, but uneven thinning occurs
Solution Approach 1:
The patent employs local quality by designing a force concentrating forming surface with specific geometry that directs forming forces to precise locations. This controlled local deformation ensures that thinning occurs uniformly in the target areas (curl, flange) while leaving critical areas (center panel, chuck wall) with consistent, adequate thickness. The local quality approach prevents the uneven thinning that would result from uniform conventional forming.
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 approach reduces material usage while maintaining strength, preventing wrinkling and ensuring even thinning, thereby reducing material weight and processing costs while being compatible with existing presses.
Implementation Method 1
The material of at least one predetermined portion of the shell is selectively stretched relative to at least one other portion of the shell, thereby providing a corresponding thinned portion
Data Source
AI summary
A shell, a container employing the shell, and tooling and associated methods for forming the shell are provided. The shell includes a center panel, a circumferential chuck wall, an annular countersink between the center panel and the circumferential chuck wall, and a curl extending radially outwardly from the chuck wall. The material of at least one predetermined portion of the shell is selectively stretched relative to at least one other portion of the shell, thereby providing a corresponding thinned portion. The tooling includes a pressure concentrating forming surface.