Laser Marking is a form of engraving used to lightly etch a surface. Similar to a shallow scratch. In manufacturing, marking is commonly used for identification, design or customization purposes.
Marking differs from engraving in a few ways. It is important to keep these differences in mind when selecting a process.
Effect on Materials
Laser engraving creates a cone-shaped indent in the surface of the material. The indent can be as deep as 1/8 of an inch. Laser marking creates a shallower cut of one-thousandth of an inch. Marking does not cut into the material. Rather it uses oxidation to remove the surface layer.
To cut through material, laser engraving requires a high-heat laser. This is important because the laser must vaporize the material. Otherwise, there can be quality issues and risks of burning. Laser marking requires a low-powered laser capable of oxidation. The laser beam is slow-moving to allow for discoloration.
Because laser marking creates a shallow indent, it is often subject to wear. Marking is recommended for safety-critical parts that should not lose their structural integrity. Or surfaces that will encounter low levels of wear and tear. Marking is often used for traceability in medical devices or aerospace parts. Engraving is recommended for items that will encounter high levels of wear and tear. Because of the deep indent, engraving will last longer.
Laser marking is broken into four types: annealing, carbon migration, foaming, and coloration.
Annealing laser marking is only used on carbon-containing metals. The process involves applying heat to the surface metal without applying aggression. This results in a solid black mark. Or depending on temperature colors can vary between shades of yellow, green and red. Annealing is used in the medical industry for internal tracking and branding.
Carbon migration laser marking is applied to most metals. During carbon migration, metal is heated causing it to bond with its carbon molecules. This process brings out metals carbon properties and results in a dark marking. Carbon migration is typically used in aerospace, jewelry engraving, and metalworking.
Foaming laser marking is strictly used on plastics where light marking is needed. The process involves creating a molten burn on the plastic until it releases foaming gas bubbles. The bubbles change the light refraction properties of plastic. Foaming is typically used with marking ink cartridges, keyboards or cosmetics packaging.
Coloration laser marking is used for metal and plastic. The process varies based on the material involved but mostly utilizes a foaming or oxidation process. This process results in a custom colored marking. Coloration is typically used for adding graphics, designs or images to a product. Coloration is common in decorative jewelry, color coating ear tags for cattle or marking bottle caps.