Multi-Layer Paint Structure for Crack-Free Deformable Sheet Metal
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Solution Overview
Problem
Conventional painting methods for sheet metal in the automotive and household appliance sectors are costly, environmentally polluting, and result in surfaces that do not meet quality requirements due to gloss loss and cracking after forming, especially when high scratch and chemical resistance are needed.
Innovation Solution
A multi-layer paint structure with a two-layer clear coat system, using fluorine-free binder chemistry, where the thermomechanical properties of the clear coats are adjusted to maintain specific ratios and softening points, ensuring the paint remains crack-free and thermally stable after forming, with optional mechanical processing to achieve desired surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional painting methods are used for sheet metal, then painting can be applied after assembly or forming, but the process is costly, environmentally polluting, and results in gloss loss and cracking after forming
Solution Approach 1:
The patent applies paint to the sheet metal substrate before forming operations. This preliminary painting allows the coating to be applied when the substrate is flat and stable, preventing the gloss loss and cracking that occur when painting after forming. The paint layer is applied in advance, then the substrate is formed, which resolves the contradiction between achieving high surface quality and maintaining ease of manufacture.
Solution Approach 2:
The patent uses a specific paint composition with controlled flexibility and hardness parameters that allows the coating to withstand forming operations without cracking or losing gloss. By adjusting the paint's physical and chemical parameters (flexibility, hardness, adhesion), the system achieves both high surface quality and manufacturing efficiency.
2Productivity
If coil coating process is used with roller application, then painting efficiency is almost 100% and VOC emissions are low, but the paint surface shows significant surface changes and gloss loss after forming
Solution Approach 1:
The patent modifies the paint composition parameters (flexibility, hardness, adhesion characteristics) to enable the coating to withstand forming operations without surface degradation. This allows the coil coating process to maintain both high efficiency and high surface quality by using a specially formulated paint system that adapts to deformation without cracking or losing gloss.
3Device complexity
If single-layer clear coat is used, then the paint system is simple, but it shows high susceptibility to cracking after heat treatment and forming
Solution Approach 1:
The patent divides the clear coat into multiple layers with different functional properties. The first clear coat layer provides flexibility and adhesion, while the second clear coat layer provides hardness and scratch resistance. This segmentation allows each layer to perform its specific function, preventing cracking during forming and heat treatment while maintaining a relatively simple overall paint system structure.
Solution Approach 2:
The patent uses a composite paint system where multiple clear coat layers with different material properties are combined. The first layer uses more flexible materials for adhesion and crack prevention, while the second layer uses harder materials for scratch and chemical resistance. This composite approach resolves the contradiction between system simplicity and crack resistance by combining materials that work synergistically.
4Ease of manufacture
If paint is applied after forming, then the substrate can be processed first, but the paint surface shows flow lines and gloss loss in deformed areas
Solution Approach 1:
The patent applies paint to the substrate before forming operations. This preliminary action ensures that the paint layer is applied when the substrate is flat and stable, preventing flow lines and gloss loss that occur when painting after forming. The substrate is formed after painting, which maintains surface quality while allowing processing flexibility.
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 produces high-quality, crack-free, and thermally stable painted metal sheets that meet decorative and protective requirements, reducing costs and environmental impact by eliminating the need for separate painting lines and ensuring consistent, even paint coverage and optimal substrate protection.
Implementation Method 1
the two-layer clear coat is based on a fluorine-free binder chemistry, such as e.g. PUR-crosslinked acrylate and polyester clear coats
Implementation Method 2
the thermomechanical properties of the two clearcoat layers in the crosslinked state are adjusted to one another
Data Source
AI summary
The invention relates to a method for producing painted deformable sheet metal, wherein a metal sheet is coated with a multilayer paint coating, wherein the paint coating comprises at least two outer clear paint coats disposed over each other, wherein the outer clear coat paint has a higher softening point in the cross-linked state than the intermediate clear coat paint thereunder, and the two top clear coat paints are adjusted with regard to the ratio of strength and elasticity so that a ratio of the tan δmax-values of the top clear coat paint to the intermediate clear coat paint of ≤ 0.8 is maintained for sheet metal having high demands with regard to foldability, and a ratio of the tan δmax-values of the top clear coat paint to the intermediate clear coat paint of ≥ 0.6 is maintained for sheet metal having high demands with regard to deep drawing capability.