1.What are its working principles and characteristics?
Selective ablation:
The high energy of the laser beam is absorbed by the coating (paint/plastic layer), causing it to rapidly heat up and vaporize (ablation).
Ideally, the laser energy is precisely controlled, removing only the surface coating without melting or severely damaging the underlying galvanized or aluminized zinc steel sheet.
The final effect is the exposure of a metallic-lustered underlying layer, creating a high-contrast pattern with the surrounding colored coating. The color of the metal layer itself (silver-white of zinc, bright white of aluminized zinc) determines the background color of the pattern.
Visual effect:
The pattern has an "intaglio" effect because slight depth differences remain after the coating is removed.
The colors are highly contrasting, making it suitable for creating logos, serial numbers, QR codes, decorative lines, artistic patterns, etc.
2.How to choose the type of laser?
Fiber lasers / MOPA fiber lasers: Currently the most suitable choice. Their wavelength (~1064nm) is effectively absorbed by most organic coatings, and precise pulse control facilitates "cold processing," reducing the heat-affected zone and preventing scorching and substrate overheating.
CO2 lasers: Can also be used for some coatings, but the heat effect may be greater, potentially leading to incomplete ablation or edge carbonization of some coatings.
Ultraviolet lasers: Extremely high precision and minimal heat effect, but high equipment cost; primarily used for extremely fine marking.
3.What are the effects of coating composition?
Polyester (PE) and silicone-modified polyester (SMP): Most commonly used, relatively easy to laser engrave, with clear results.
Fluorocarbon (PVDF): Due to its excellent weather resistance and chemical stability, it is more difficult to ablate. It requires higher laser energy or optimized parameters, and the edges may not be as sharp as polyester coatings.
Color: Dark coatings (especially black) absorb laser energy more efficiently and are easier to engrave. Light-colored or metallic coatings (containing aluminum powder) have high reflectivity, requiring parameter adjustments to ensure effective ablation.
4.How can process parameters be optimized?
Power, speed, frequency, and fill spacing: These require precise adjustments for specific coating types, colors, and thicknesses. The goal is to cleanly remove the coating with the lowest effective energy while:
Minimizing thermal impact: Preventing yellowing and carbonization of the coating edges.
Protecting the substrate: Avoiding excessive ablation that could damage the zinc layer and compromise corrosion resistance.
Ensuring pattern quality: Clear lines and high contrast.
5.What are the advantages and potential problems?
Advantages:
Non-contact, high precision: Capable of engraving complex graphics, fine lines, and tiny text.
Permanent marking: Patterns are wear-resistant and do not easily peel off.
No ink consumables required: Environmentally friendly and with low operating costs.
Automation integration: Easy to integrate into production lines for online marking.
Personalization and anti-counterfeiting: Ideal for production traceability, brand identification, and customized decoration.
Potential Issues and Challenges (Must be assessed):
Sacrificing Local Corrosion Resistance: This is the most critical drawback. The protective coating is removed from the engraved area, making the exposed metal (even the galvanized layer) more susceptible to corrosion. For outdoor applications, risk assessment is necessary, or secondary localized protection (such as a clear rust-preventive coat) should be considered after engraving.
Color and Effect Limitations: Only a contrast of "original metal color vs. coating color" can be achieved. Color or gradient effects cannot be produced.
Substrate Damage Risk: Incorrect parameters can lead to melting, discoloration (heat oxidation), or even perforation of the underlying metal.
Hazardous Fumes: Ablation of the coating generates fumes and particulate matter, requiring a powerful ventilation and filtration system to protect operator health and maintain lens cleanliness.
Speed and Cost: Intricate, large-area engraving is slow, impacting production efficiency.