Pre-Coated Can Wall Ironing for Nestable Tapered Containers
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Solution Overview
Problem
Current can manufacturing processes using pre-coated metal face challenges such as damage to coatings, uneven wall thickness, and the inability to achieve significant thickness reduction due to high frictional forces and burr formation, which limits the production of nestable cans with tapers or steps.
Innovation Solution
A method involving a wall-ironing process where the wall-ironing die moves axially over the closed end of the cup, reducing thickness and increasing height while avoiding the open end, and using tools with varying diameters to form flanges and tapers, allowing for the production of nestable cans with reduced coating damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If wall-ironing is performed on pre-coated metal to reduce wall thickness, then material cost is reduced, but coating damage occurs
Solution Approach 1:
The coating is applied to the metal sheet before the wall-ironing process, allowing the coating to be pre-positioned and protected during subsequent forming operations. The coating is cured after wall-ironing to complete the protection
Solution Approach 2:
The wall-ironing die profile is made adjustable along the axial direction, allowing dynamic adaptation to different can specifications and wall thickness reduction requirements, optimizing the ironing process for each specific application
2Stability of the object's composition
If significant wall thickness reduction is achieved through wall-ironing, then nestability is improved, but burr formation and splitting occur at the open end
Solution Approach 1:
The wall-ironing process is segmented into multiple stages with progressively smaller die diameters, allowing controlled thickness reduction throughout the wall rather than concentrated at one location, preventing burr formation and splitting
Solution Approach 2:
The wall thickness reduction parameters are optimized by adjusting the die profile and ironing conditions to achieve uniform thinning distribution, preventing excessive reduction at the open end that would cause burrs and splitting
3Ease of manufacture
If pre-coated metal is used instead of uncoated metal, then manufacturing cost is reduced, but frictional forces increase during wall-ironing
Solution Approach 1:
The coating is applied and cured before wall-ironing, creating a protective layer that reduces friction between the metal and die surfaces during the ironing process, allowing pre-coated metal to be used without excessive frictional forces
Solution Approach 2:
The coating properties and ironing parameters are optimized to balance cost-effectiveness of pre-coated metal with acceptable frictional forces during processing
4Manufacturing precision
If the wall-ironing die passes beyond the open end of the cup, then complete wall ironing is achieved, but the raw edge becomes uneven and trimming is required
Solution Approach 1:
The wall-ironing die profile is designed to apply different levels of ironing to different regions of the wall, with reduced or no ironing at the open end region, maintaining adequate wall thickness where needed while avoiding burr formation that would require trimming
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 method enables the production of cans with reduced coating damage, increased nestability, and the ability to form tapers or steps without splitting, while maintaining cost-effectiveness by using pre-coated metal, thus overcoming the limitations of traditional processes.
Implementation Method 1
a first manufacturing step is typically to blank and draw a number of shallow cups... The press may comprise a plurality of stations operating in parallel... a shallow-drawn cup is re-drawn over a reciprocating wall-ironing punch, to form a can body... The can body is then pulled through a number of wall-ironing dies that each have progressively smaller diameters, such that the wall thickness is reduced
Implementation Method 2
compressed air is introduced into the can through the wall-ironing punch to prevent the can walls from collapsing inwards as the can body is stripped from the wall-ironing punch
Data Source
AI summary
A method of reducing a thickness and increasing a height of a cylindrical wall of a metal cup to form a can body comprises positioning a wall-ironing punch (40) inside the cup, moving an annular wall-ironing die (24) axially over the closed end of the cup towards the open end of the cup, but not beyond the open end of the cup, in order to iron the cylindrical wall from the closed end up to a position axially spaced from the open end and moving the wall-ironing die (24) back in an opposite direction to remove the can body from the die (24). Methods of altering a diameter of one or more regions of a can body are also disclosed.