Metal Beverage Container Blow Molding with Preheated Work-Hardened Preform
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Solution Overview
Problem
Existing methods for manufacturing metal beverage containers with complex shapes, such as those resembling glass bottles, face challenges in achieving sufficient axial strength while minimizing weight and cost, and heating processes can degrade the metal's strength and structure.
Innovation Solution
A method involving a work-hardened metal preform is preheated to limit heat application to the open and closed ends, then inserted into a segmented mold where pressure is increased in a step function to radially expand the sidewalls, allowing the container to take the desired shape without compromising the dome-shaped bottom's strength, all done at room temperature to prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heating is applied to the metal preform to enable complex shaping, then the metal becomes more formable, but the axial strength and structural integrity of the final product deteriorates
Solution Approach 1:
The preform is work-hardened in advance through a draw-redraw or back-extrusion process to develop a recrystallized or recovered microstructure before the final forming operation. This preliminary strengthening allows the metal to be shaped into complex forms without requiring subsequent heating that would compromise strength.
Solution Approach 2:
The metal's microstructure is transformed through work hardening and controlled deformation processes, changing its physical parameters to achieve both formability and strength. The gauge is optimized to thin gauges (0.004-0.015 inches) with specific microstructural characteristics that enable complex shaping while maintaining axial strength.
2Strength
If thicker metal is used to improve axial strength, then the strength criteria are met, but the weight and manufacturing cost increase
Solution Approach 1:
The metal is transformed through work hardening and microstructural recovery to achieve superior strength-to-weight ratio. Thin-gauge metal (0.004-0.015 inches) is processed to develop a recrystallized or recovered microstructure that provides high axial strength without requiring increased thickness, thereby reducing weight.
Solution Approach 2:
The preform structure combines thin-gauge metal with a specifically engineered microstructure (recrystallized or recovered) to create a composite-like material system that achieves the required axial strength at minimal weight. The work-hardened state acts as a structural enhancement without adding mass.
3Productivity
If the preform is expanded rapidly to achieve complex shapes, then productivity increases, but deformation and defects occur
Solution Approach 1:
The preform is pre-shaped with a closed-end tube structure and optimized profile before the final blow-molding operation. Threads and bottom profiles are pre-formed to assist with the final shaping, allowing rapid expansion without deformation because the basic structure is already in place.
Solution Approach 2:
The forming process uses dynamic control of the expansion sequence, allowing the preform to be rapidly shaped into complex forms. The preformed structure and controlled microstructure enable the metal to respond dynamically to the forming forces without permanent deformation or defects.
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 production of metal beverage containers with complex shapes that maintain axial strength and prevent deformation, reducing the need for costly materials and heating processes, thereby improving manufacturing efficiency and product quality.
Implementation Method 1
preheating the body portion of the preform in a manner that limits heat being applied to the open portion and closed end portion of the preform
Implementation Method 2
blow molding the preform by increasing the applied pressure using a step function to a second pressure level after the mold is closed, the increase of the pressure from the first pressure level to the second pressure level to occur in less than about 0.2 seconds to cause the preform to take a shape defined by the mold
Implementation Method 3
applying a pre-pressure by delivering a fluid into the inside of the preform at a first pressure level prior to closing the multiple segments of the mold
Data Source
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AI summary
A system and method of manufacturing a metal vessel may include providing a preform formed of a work hardened metal that includes an open portion, a closed end portion, and body portion. The body portion of the preform may be preheated in a manner that limits heat being applied to the open portion and closed end portion of the preform. The preheated preform may be blow molded.