1.Why do we say "it's possible, but there are risks"?
Coating Crack Risk:
Ductility Challenge: During rolling, the steel substrate and the surface coating are stretched and bent together. If the coating's ductility (especially the topcoat) is insufficient and it cannot deform synchronously with the metal substrate, fine cracks or even large-area peeling will occur.
Film Performance: Ordinary polyester (PE) coatings generally have low ductility and pose a higher risk. High-performance polyvinylidene fluoride (PVDF) or high-durability polyester (HDP) coatings have better ductility and are relatively more resistant, but are still not 100% safe.
Zinc Layer Damage Risk:
The substrate of color-coated coils is usually galvanized or aluminized zinc sheet. Severe plastic deformation can damage the integrity of the coating, especially at the edges of the pattern. Once the zinc layer is damaged, the corrosion resistance of the sheet will be greatly reduced, and the embossed areas may become the starting point for future rusting.
Appearance Damage Risk:
Rolling equipment and dies may rub against the coating surface, causing scratches, indentations, or uneven gloss, affecting the final appearance.
High processing difficulty:
It requires extremely precise adjustments to the pressure, speed, and die curvature of the rolling equipment, and may require trial runs for specific coatings. The process control is complex, resulting in a high scrap rate.
2.What are the advantages and disadvantages of embossing before painting?
Advantages:
Best Quality: The coating completely covers the surface of the formed sheet, eliminating the problem of cracking due to later deformation, and providing the best corrosion resistance.
Perfect Appearance: The coating is uniform and the color is consistent, effectively showcasing the three-dimensional effect of the pattern.
Wide Range of Options: It can process any coating (PE, SMP, PVDF, etc.) without being limited by ductility.
Disadvantages:
Usually requires customization from color-coated steel sheet manufacturers, resulting in high production barriers, large minimum order quantities, longer delivery cycles, and higher costs.
3.What are the applicable scenarios for embossing after color coating rolls?
For temporary buildings or interior decorations where appearance and durability requirements are not high, rigorous sample testing is necessary.
4.What are the applicable scenarios for embossing before painting?
Permanent buildings requiring high quality, durability, and aesthetics, such as roofs/walls of high-end factories and public facilities.
5.If embossing with pre-coated colored rolls is absolutely necessary, what suggestions do you have?
First, conduct sample testing: Always use the planned pre-coated coils (including specific coatings and thicknesses) for actual rolling, then check for coating cracking, adhesion (perform a cross-cut test), and zinc layer damage.
Select suitable materials: Prioritize pre-coated coils with high-performance coatings such as PVDF or HDP, and thicker zinc layers (e.g., AZ150, Z275).
Control pattern depth: Avoid designing overly deep or sharp patterns to reduce deformation.
Communicate thoroughly with the processing plant: Ensure the processing plant has relevant experience and can adjust process parameters.