Seamless Can Bottom Structure for Pressure Resistance Without Reforming
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Solution Overview
Problem
Conventional seamless can bodies face issues with blacking and agglutination during bottom reforming, require costly cleaning steps, and have limitations in thinning sheet thickness due to extension and thinning of raw metal material, leading to suboptimal pressure resistance distribution and increased equipment complexity.
Innovation Solution
A seamless can body design with a tubular body section and can bottom section featuring varying sheet thicknesses (t1 < t2 < t3 < t4 < t5) and a ring groove, manufactured through two molding steps to enhance pressure resistance and reduce weight, eliminating the need for bottom reforming and cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bottom reforming is performed by pressing with a molding roller, then pressure resistance is enhanced, but blacking and agglutination occur at the pressed part
Solution Approach 1:
The invention extracts and eliminates the bottom reforming step that causes blacking and agglutination. Instead of pressing the can bottom with a molding roller, the patent uses a draw-formed can body with optimized geometry that achieves pressure resistance without the harmful pressing operation.
Solution Approach 2:
Rather than enhancing pressure resistance by compressing the can bottom (conventional approach), the invention inverts the approach by using draw-forming that naturally creates optimized thickness distribution and geometric strength, eliminating the need for compressive pressing.
2Strength
If bottom reforming is performed, then pressure resistance is enhanced, but cleaning steps are required due to lubricant application
Solution Approach 1:
The invention removes the bottom reforming step that necessitates lubricant application and subsequent cleaning. The draw-forming process creates the required pressure resistance through geometric design and controlled thickness distribution without requiring additional lubrication and cleaning operations.
3Strength
If bottom reforming is performed, then pressure resistance is enhanced, but sheet thickness of raw sheet cannot be sufficiently thinned
Solution Approach 1:
The invention performs thickness optimization during the draw-forming process itself, before any bottom reforming would occur. By controlling the draw-forming parameters, the can body is created with optimized thickness distribution that provides pressure resistance while enabling use of thinner raw sheets for weight reduction.
Solution Approach 2:
The invention changes the approach from post-draw reforming to controlled draw-forming parameters. By adjusting draw ratio, blank holder pressure, and tooling geometry during the forming process, optimal thickness distribution is achieved that provides pressure resistance while allowing thinner raw material usage.
4Strength
If two-piece can body with thicker grounding section is used, then pressure resistance is enhanced, but equipment complexity and cost increase
Solution Approach 1:
The invention merges the can body forming and bottom formation into a single integrated draw-forming process. This eliminates the need for separate bottom reforming equipment and complex multi-step manufacturing lines, achieving pressure resistance through unified process control rather than sequential operations.
Solution Approach 2:
The draw-forming tooling performs multiple functions simultaneously: it forms the can body shape, controls thickness distribution, and creates the pressure-resistant bottom geometry in one operation, eliminating the need for specialized bottom reforming equipment.
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 design allows for thinner raw sheet usage, reducing material and production costs, while enhancing pressure resistance and preventing buckling, thus achieving weight reduction and environmental benefits.
Implementation Method 1
a can body section (10) and a can bottom section (20) of a seamless can body (1), in which the can body section (10) is molded by drawing and ironing
Implementation Method 2
the sheet thickness gradually increases from the outer circumferential bottom section (20a) toward the inside end section (20c)... the can bottom section (20) is required to have strength (pressure resistance) for resisting deformation due to internal pressure
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(c)
AI summary
[Object] To provide a seamless can body in which the sheet thickness of a raw sheet (blank) is reduced, pressure resistance of a can bottom is enhanced, buckling is restrained, and problems with blacking and cleaning are solved, and a manufacturing method of the seamless can body. [Solving Means] A seamless can body 1 having a tubular body section 10 and a can bottom section 20. The can bottom section 20 includes an outer circumferential bottom section 202a extending from a lower end of the tubular body section 10 such as to decrease in diameter toward the inside and an annular grounding section 202b positioned further inside than the outer circumferential bottom section 202a. In a case where t1 is the sheet thickness of the outer circumferential bottom section 202a and where t2 is the sheet thickness of the annular grounding section 202b, the relation of t2 > t1 is satisfied.