Metal Preform Wall Thickness Gradient for Pressure Forming
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Solution Overview
Problem
Existing methods for pressure-ram-forming metal containers with complex shapes, such as bottle shapes, face challenges in controlling the temperature gradient, which can be affected by production speed, preform size, and tooling setup, leading to difficulties in achieving progressive expansion without blow-outs.
Innovation Solution
A method involving a hollow metal preform with a wall thickness gradient, where the thickness decreases progressively from the closed end to the open end, allowing for progressive outward expansion when subjected to internal fluid pressure, mimicking the effect of a temperature gradient without its associated challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a temperature gradient is induced in the preform to control progressive expansion, then the onset of preform expansion can be controlled, but the temperature gradient control becomes complex and is adversely affected by production speed, preform size and tooling setup
Solution Approach 1:
The invention changes the physical parameter from temperature gradient to wall thickness gradient. Instead of controlling expansion through thermal effects, the preform is designed with varying wall thickness where the wall is thinner at the open end and thicker at the closed end. This geometric parameter change enables progressive expansion control without the complexity of temperature management systems.
Solution Approach 2:
The invention replaces the thermal field system (heaters, temperature control) with a mechanical/structural system (varying wall thickness). The mechanical structure of the preform itself controls the expansion behavior through its geometric properties, eliminating the need for complex thermal management during the forming process.
2Shape
If the preform is subjected to internal fluid pressure to expand it outwardly, then the container shape can be formed, but blow-outs may occur without proper progressive expansion control
Solution Approach 1:
The preform is designed with non-uniform wall thickness distribution, creating local quality variations. The wall is intentionally made thinner at the open end and thicker at the closed end, so that different regions of the preform have different expansion characteristics. This local quality difference ensures progressive expansion from the open end toward the closed end, preventing blow-outs while forming the desired container shape.
3Ease of manufacture
If a uniform wall thickness preform is used, then the manufacturing process is simpler, but the container bottom strength is insufficient
Solution Approach 1:
The preform incorporates local quality variations through non-uniform wall thickness. The closed end (bottom) region is designed with greater wall thickness to provide enhanced strength and structural integrity, while the side wall and open end regions have reduced thickness. This localized thickness variation ensures both bottom strength and ease of expansion during 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 enables the formation of containers with a stronger bottom and thinner top, enhancing the container's structural integrity and ease of closure formation, while avoiding the complexities of temperature gradient control, thus improving the efficiency and reliability of the pressure-ram-forming process.
Implementation Method 1
The preform is subjected to internal fluid pressure to expand the preform outwardly into substantially full contact with the die wall
Implementation Method 2
the preform as disposed in the die cavity has a wall thickness gradient such that the preform wall thickness decreases progressively from the closed end toward the open end
Data Source
Figure 1~2B
Figure 3
Figure 4A~4D
AI summary
A method of forming a bottle-shaped or other contoured metal container by providing a hollow metal preform having a closed end and a wall thickness that decreases progressively in a direction away from the closed end, and subjecting the preform to internal fluid pressure to cause the preform to expand against the wall of a die cavity defining the desired container shape. The method may be employed in pressure-ram-forming procedures wherein a punch is advanced by means of a backing ram into the die cavity to displace and deform the closed end of the preform.