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  3. [Laser Selection according to Material] Plastic

[Laser Selection according to Material] Plastic

This section introduces various 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 required the printing plate to be changed. With a laser marker, you can handle it flexibly by just changing the program.

2: Surface layer peeling

Remove/engrave the surface layer with a laser.

(Example) Half cut

Use a laser marker to process a cutting section. A cutter was used in the conventional method; however, there were problems such as difficult adjustment and time-consuming changeover between product types. Moreover, the method incurred costs for replacing the blade and there was 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, the damage of marking the target can be 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 changes to a darker color.

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 (White)

Suitable Models

MD-V9900 Series 3-Axis YVO4 Laser Marker

Print Quality
  • - High contrast printing is achievable without causing harm to the surface of the material.
  • - Trademarks and custom logos printed on product surfaces are permanent.
Points to Note
  • - The amount of contrast achievable in marking is dependant on the type of plastic used.
  • - CO2 laser markers do not typically discolor plastic surfaces.
Benefits of 3-Axis Lasers
  • - 3-Axis marking allows for precise marking of characters on complex shapes without distortion.
  • - Variable-focal-length printing is possible without setup changes on products of various diameters and curved surfaces.


EPOXY (Black)

Suitable Models

MD-V9900 Series 3-Axis YVO4 Laser Marker
MD-F3100/5100 Series 3-Axis Fiber Laser Marker

Print Quality
  • - Printing is generally white, allowing for easy transition from ink-jet printing or stamp printing.
  • - Damage to the targets surface is minimal and marks are permanent.
Points to Note
  • - The YVO4 laser prints at a more shallow depth and with more precision than a CO2 laser.
  • - Purposely de-focusing the laser allows for more uniform, higher contrasting marks on some epoxies.
Benefits of 3-Axis Lasers
  • - It is possible to mark in a 300 mm X 300 mm area and to maintain precise, uniform marking without the use of any external devices such as an X Y stage.
  • - Internal focal point adjustment is possible and can be automatically programmed into the marking parameters via the Marking Builder software.


PET

Suitable Models

ML-Z9500 Series 3-Axis CO2 Laser Marker

Print Quality
  • - Contrasting print that is permanently etched into the surface of the material.
  • - Printing on thin films is possible without causing pin holes or marks that burn through.
Points to Note
  • - Pin holes can appear as a result of overheating when printed under high-power.
  • - Use of a short wavelength laser (9.3 μm) for clear printing with minimal damage.
Benefits of 3-Axis Lasers
  • - Clear printing is possible, even on curved surfaces such as PET bottles.
  • - With a variable focal point, the ML-Z Series can automatically adjust to compensate for curved surfaces and even different sized targets running on the same production line.

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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