Metallic Worked Surface Roughness Control for Scratch-Free Ironing
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Solution Overview
Problem
Existing draw-ironing work methods using hard thin films, such as diamond-like carbon, are prone to peeling and have low durability, making them ineffective under high surface pressure conditions, particularly in the production of beverage cans, and fail to prevent metal adhesion and scratches during the wet ironing process.
Innovation Solution
A draw-ironed blank can with a surface roughness ratio Ra1/Ra2 of 0.5 to 1.5 is produced using an ironing die with a diamond film, ensuring the worked surface remains smooth and scratch-free, even after producing a large number of cans, by maintaining a diamond film with a surface roughness of not more than 0.1 μm and using a multi-angle spectrophotometer to evaluate the brightness and specularity of the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard thin film of diamond-like carbon is used on the die surface to suppress metal adhesion, then the surface hardness and adhesion resistance are improved, but the film durability and resistance to peeling deteriorate under high surface pressure conditions
Solution Approach 1:
The patent applies a composite coating structure consisting of a base coat layer and a top coat layer with different properties. The base coat provides adhesion and corrosion resistance, while the top coat provides hardness and wear resistance. This composite structure resolves the contradiction by combining materials with complementary properties rather than using a single material that must compromise between hardness and durability.
Solution Approach 2:
The patent applies different coating layers with specific properties to different regions or functions within the coating system. The base coat layer is optimized for adhesion to the die substrate and corrosion resistance, while the top coat layer is optimized for hardness and wear resistance. This local differentiation of material properties allows each layer to perform its specific function optimally without compromising the other.
2Productivity
If continuous production of aluminum cans is increased to improve productivity, then the production efficiency is improved, but metal adhesion to the die increases causing surface scratches
Solution Approach 1:
The patent applies a pre-formed protective coating on the die surface before the metal forming process begins. This preliminary protective layer prevents metal adhesion from occurring during continuous production, allowing high productivity to be maintained without the harmful effect of metal adhesion and surface scratches.
Solution Approach 2:
The protective coating acts as an intermediary layer between the die surface and the aluminum metal. This intermediate layer prevents direct contact and adhesion between the metal and die, allowing continuous high-speed production without metal transfer to the die surface.
3Manufacturing precision
If the die surface roughness is reduced to improve surface quality, then the specularity is improved, but the susceptibility to metal adhesion increases
Solution Approach 1:
The multi-layer coating system provides both smooth surface finish for specularity and adequate surface energy control for adhesion resistance. The composite structure allows the top layer to be very smooth while the underlying layers provide the necessary adhesion properties, resolving the contradiction between surface quality and adhesion resistance.
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 effectively suppresses scratches and maintains surface quality throughout the production process, ensuring high specularity and preventing metal adhesion on the die, allowing for continuous production without significant increases in surface roughness or scratches, even after producing over 35,000 cans.
Implementation Method 1
the hard film of this kind has problems; e.g., the hard film is likely to be easily peeled off, has a low durability and its effect for suppressing the adhesion is not enough under conditions where high surface pressures are exerted
Implementation Method 2
the hard film of this kind has problems; e.g., the hard film is likely to be easily peeled off, has a low durability
Data Source
AI summary
A metallic worked article suppressing the worked surfaces from being scratched during the plastic work that is conducted aiming at reducing the thickness or decreasing the diameter. The metallic worked article has a reduced thickness or a decreased diameter as obtained through the plastic work, wherein on the worked surface thereof, the ratio Ra1/Ra2 of an arithmetic mean roughness Ra1 measured in a direction at right angles with the direction of working and an arithmetic mean roughness Ra2 measured in the direction of working, is from 0.5 to 1.5.