Dry-DWI Can Body Forming to Prevent Polymer Edge Hairs
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Solution Overview
Problem
The production of can bodies from polymer coated metal sheets using the dry-DWI process is hindered by the formation of 'hairs' at the edge of the can body, which can lead to tooling contamination and potential damage, and requires rinsing, negating the advantages of the dry process.
Innovation Solution
The method involves reducing the blank holder force on the redraw sleeve just before the edge of the initial cup enters the redraw die's operative part, and using a reduced radius for the redraw die and sleeve to prevent pinching and wrinkling, allowing for controlled stretching and elongation of the polymer coated metal sheet during the cupping and redrawing stages, thereby minimizing hair formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If polymer coated metal sheet is used in dry-DWI process, then lubricant usage is minimized and washing is eliminated, but hair formation occurs at the can body edge
Solution Approach 1:
The patent applies preliminary action by modifying the polymer coating properties before the DWI process. The coating is designed with specific characteristics (softness, thickness, composition) that enable it to prevent hair formation during subsequent drawing operations. This preliminary preparation of the material properties resolves the contradiction by ensuring the coating can withstand deformation without scraping off, thus preventing hair formation while maintaining the dry process advantages
Solution Approach 2:
The patent employs parameter changes by adjusting the polymer coating's physical and chemical parameters. Specifically, the coating's softness, thickness, and composition are optimized to prevent hair formation. By changing these parameters, the coating becomes sufficiently compliant to prevent scraping during deformation while maintaining adhesion to the metal substrate, thus eliminating harmful hair formation without requiring lubricants or subsequent washing
2Ease of manufacture
If polymer coating layer is softer than metal substrate, then coating deforms more easily during drawing, but polymer may be scraped off forming hairs
Solution Approach 1:
The patent applies local quality by creating a non-uniform coating structure with different properties at different locations or depths. The coating may have a softer outer layer for deformability and a tougher inner layer for adhesion, or varying thickness across the coating. This localized differentiation allows the coating to deform easily during drawing while preventing scraping and hair formation
Solution Approach 2:
The patent employs composite materials by using a multi-layer polymer coating system or a polymer coating with composite structure. The coating comprises multiple layers with different properties - one layer provides softness for easy deformation while another layer provides strength and adhesion to prevent scraping. This composite structure resolves the contradiction between deformability and hair prevention
3Strength
If copious lubricants are used in DWI process, then tool surface wear is prevented and heat is cooled, but thorough washing is required
Solution Approach 1:
The patent applies self-service by making the polymer coating perform multiple functions simultaneously. The coating acts as a built-in lubricant during deformation, protects the tool surface from wear, and prevents hair formation. This eliminates the need for external lubricants and subsequent washing operations, as the coating serves all protective functions inherently
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 effectively prevents hair formation, reduces the need for rinsing, and allows for a more robust and controlled dry-DWI process with increased wall height and reduced ironing requirements, enhancing the efficiency and cleanliness of the can body production.
Implementation Method 1
The polymer coating layer acts as lubricant
Implementation Method 2
the polymer coating layer deforms more easily than the metal substrate
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4
AI summary
This invention relates to an improved method of producing can bodies from a polymer coated metal substrate by the drawing and wall-ironing process.