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This section introduces a variety of information, from plastic marking/processing principles to laser features according to wavelength.
The optimal laser markers and marking examples are provided for each category, including ABS, epoxies, and PET marking.

Major types of marking/processing

1: Paint peeling

Peel the paint or printing on the target surface to bring out the contrast with the color of the base material.

(Example) Automobile instrument panel switch

When the design is changed, conventional methods using printing or stamps require the printing plate to be changed. With a laser marker, you can adjust quickly by simply changing the program.

2: Surface layer peeling

Remove/engrave the surface layer with a laser.

(Example) Half cut

A laser marker can be used to easily process a cutting section. A cutter is used in the conventional method; however, there are problems such as difficult adjustment and time-consuming changeover between product types. Moreover, this method incurred costs for replacing the blade and there is a risk of the blade being left in the product.

3: Color development

Irradiate a plastic target with a laser to develop a color in the target itself.

(Example) Wide-area marking on LSI

By using laser radiation to develop a color instead of engraving the plastic, damage from marking the target is minimized.

4: Welding

Use the heat of laser radiation to weld and join plastic parts.

(Example) Welding of transparent plastic and colored plastic

Traditional welding can cause vibration which may affect the product or produce burrs. Since laser welding does not make contact with products, it won't damage them or produce burrs.

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Mechanism of plastic color development

1: Foaming

When the base material is irradiated with a laser, gas bubbles are generated inside the material due to the thermal effect of the radiation. Gasified, evaporated bubbles are contained in the surface layer of the base material and create a whitish swelling. When the base material has a dark color, the swelling is highly visible and typically paler than it was before marking.

(Example) Base material color: Black ➝ Changes to Gray, Red ➝ Changes to Pink

2: Condensing

When the base material absorbs the laser energy, the thermal effect increases the molecular density.
The molecules are condensed and the color becomes darker.

3: Carbonization

When the area continuously receives high energy, macromolecules of the element around the base material are carbonized and turn black.

4: Chemical change

The “pigment” elements in the base material always contain metallic ions. The laser radiation changes the crystal structure of the ions and the hydration level in the crystal. Consequently, the composition of the element itself changes chemically, resulting in color development due to the increased intensity of the pigment.

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Ratio of absorption into plastic

Ratio of absorption into materials depending on wavelengths

The graph on the left shows the transmission ratio of a fundamental laser (1064 nm) and a green laser (532 nm) for various plastic materials. For PVC, ABS, and polystyrene, both fundamental and green lasers show low transmission ratio and high absorption ratio, which ensures good marking. On the other hand, the transmission ratio for polyimide is about 30% with a green laser (532 nm) but more than 90% with a fundamental laser (1064 nm). The absorption ratio varies greatly depending on the wavelength.

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ABS Plastic

Black-Annealed Marking / White Marking

Irradiation from the laser light results in a black / highly visible white color on the surface of the plastic. Marking provides a printing-like finishing on designs and other surfaces that cannot be erased.

Selection factors

Factors such as the degree of coloring and the density depend on the nature of the target plastic. Hybrid laser markers capable of producing a high peak power even at the fundamental wavelength are optimal. CO2 laser markers do not typically discolor plastic surfaces.

Recommended model

Epoxy Plastic

White Marking

Markings are white and clear, making for an ideal replacement for stamps, labels, and printing. The highly visible, print-like finishing does not disappear like ink.

Selection factors

Shifting the focal point for defocused marking allows for high-grade printing with good visibility, all while keeping the engraving depth to a minimum.

Recommended model

PET Plastic

Marking that appears as if the white characters are floating from the surface is possible with transparent/translucent PET plastic. From PET bottles to thin film materials, marking can be achieved with no pin holes.

Selection factors

Pin holes can appear as a result of overheating when marking under high power. Using a laser with a short wavelength (9.3 μm) enables clear marking with minimal damage.

[Standard wavelength] (Conventional methods) Damage is excessive and engravings are deep and rough / [Short wavelength] (ML-Z) Damage is minimal and engravings are shallow and sharp

Recommended model

Learn more about plastic marking and processing. “What is the principle behind contrast marking?” “What is the absorption rate for each material?” Learn the ins and outs of laser marking with a focus on plastic marking and processing. / Catalog Download


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