Impact Extrusion Tooling for Thickened Container Rim Preforms
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Solution Overview
Problem
Conventional impact extruded metal preforms with constant tubular wall thickness face challenges in expansion shaping due to uneven material thickness, leading to weak annular regions and potential container failure under pressure, especially in aerosol containers where internal pressures cause excessive stress at the rolled-in rim section.
Innovation Solution
A method and tooling for impact extrusion that allows for the creation of preforms with variable sidewall thickness, utilizing a punch with a transition region and extrusion points to form a tubular wall with a thicker transition wall thickness, which strengthens the rim section and reduces bending stress during pressure ram forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional impact extrusion with constant wall thickness is used, then manufacturing simplicity is maintained, but structural strength at the rim section is insufficient under internal pressure
Solution Approach 1:
The patent applies local quality by creating variable wall thickness in the preform, with a thicker transition wall portion at the rim section and a thinner sidewall portion. This is achieved through a multi-stage extrusion process using a punch with specific geometric features (shoulder, land portion, and extrusion point) that controls material flow to produce localized thickness variations. The thicker rim section provides enhanced strength to withstand internal pressures, particularly in aerosol containers, while the overall device complexity is managed by integrating this into the existing impact extrusion process.
2Strength
If variable sidewall thickness is implemented, then pressure resistance is improved, but material distribution uniformity deteriorates
Solution Approach 1:
The patent employs preliminary action by designing the punch geometry with a shoulder and land portion that pre-determine the material distribution before the final forming stage. The land portion width and extrusion point position are carefully selected to control the material flow and achieve the desired variable thickness profile. This preliminary geometric configuration ensures that the thicker transition wall portion forms correctly during extrusion, providing the necessary pressure resistance while maintaining controlled material distribution through the designed tooling geometry.
3Stability of the object's composition
If thicker transition wall portion is created, then rim stability is enhanced, but material usage increases
Solution Approach 1:
The patent optimizes material usage by applying local quality principles - the thicker transition wall portion is localized only where structurally necessary (at the rim section), while the sidewall portion maintains a thinner, more material-efficient profile. The variable thickness design concentrates material where pressure resistance and rim stability are critical, reducing overall material consumption compared to a uniformly thick-walled preform, while still providing enhanced stability at the rim section to prevent unrolling under internal pressure.
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
The method enhances the pressure resistance and stability of expanded containers by creating a thickened rolled-in rim that can withstand internal pressures without unrolling, allowing for the use of preforms in both carbonated beverages and aerosol containers, and reduces material usage while maintaining structural integrity.
Implementation Method 1
a metal blank is impacted at such force that the metal is transformed into a plastic state in which the metal will actually flow
Implementation Method 2
A rearward end of the land portion is positioned at a different spacing from the axis than a forward end of the land portion at the peripheral shoulder
Data Source
Figure 1A~1C
Figure 2
Figure 3A
AI summary
A hollow preform impact extruded from a metal billet to produce a progressing wall at a transition wall thickness. An axially forward portion of the progressing wall is ironed by extrusion past an extrusion point to form a sidewall portion of a lesser thickness. Extruding is stopped while some of the billet remains to form the closed bottom end. The preform has a bottom portion, a sidewall portion and a transition wall portion extending between the bottom portion and the sidewall portion. The transition wall portion is thicker than the sidewall portion and can be formed into at least part of the rim of an expansion shaped container. An impact extrusion punch has a central axis, an axially forward, impact surface for impacting metal to be extruded, a transition region for directing material displaced by the impact surface and a rear extrusion point for ironing material extruded past the transition region.