How does laser marking plastic work?

Laser marking plastic is a non-contact process that uses a focused laser beam to create permanent marks, such as text, logos, or barcodes, on plastic surfaces. The process works by altering the plastic's surface properties through various mechanisms, depending on the type of plastic and the laser used. Here’s how it works:

1. Laser Absorption and Interaction

• The laser beam (typically fiber, CO₂, or UV laser) is directed onto the plastic surface.

• The plastic absorbs the laser energy, which causes a chemical or physical change in the material.

2. Marking Mechanisms for Plastics

Different plastics react differently to laser marking, leading to various marking effects:

A. Color Change (Foaming or Carbonization)

• Foaming: Some plastics (like ABS or PVC) heat up and produce gas bubbles, creating a light-colored, raised mark.

• Carbonization: The laser burns the plastic slightly, leaving a dark mark (common for light-colored plastics).

B. Engraving (Material Removal)

• The laser vaporizes a thin layer of the plastic, creating a recessed mark (common for deeper engravings).

C. Chemical Change (Photochemical Reaction – UV Lasers)

• UV lasers (e.g., 355 nm wavelength) break molecular bonds without excessive heat, causing a color change without melting (ideal for sensitive plastics).

D. Bleaching (For Dark Plastics)

• The laser removes pigments from the surface, creating a lighter-colored mark (common for black plastics).

3. Factors Affecting Laser Marking Quality

• Laser Wavelength:

• CO₂ (10.6 µm): Good for engraving but may melt some plastics.

• Fiber (1.06 µm): Better for dark plastics (carbonization).

• UV (355 nm): Best for precise, heat-free marks on sensitive plastics.

• Plastic Type: Additives (like flame retardants or fillers) affect marking quality.

• Laser Power & Speed: Higher power can engrave deeper, while lower power may only discolor the surface.

• Pulse Frequency: Adjusting pulse rate can improve contrast and precision.

4. Advantages of Laser Marking Plastics

• Permanent & High-Contrast Marks

• No Ink or Chemicals (Eco-friendly)

• High Precision (Suitable for tiny barcodes, QR codes)

• Fast & Automated (Ideal for mass production)

5. Common Applications

• Product branding (logos, text)

• Serial numbers & barcodes

• Medical device marking (biocompatible plastics)

• Electronics (circuit board labels)

Conclusion

Laser marking plastic works by selectively altering the surface through heat or photochemical reactions, resulting in high-contrast, durable marks without physical contact. The best results depend on choosing the right laser type and settings for the specific plastic material.

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