There are many factors that need to be taken into consideration when choosing the right laser for a marking application. In addition to the size and type of mark, the amount of time allotted for marking, and the available space for placing equipment in an automated production environment, the attributes of the material being marked can dictate the laser required.
Material Color
- Dark colors absorb more light than lighter colors.
- Painted colors have little effect since the laser usually vaporizes away paint.
- Additives can be used in plastics to create a color change when the material is marked.
Surface Finish
While surface finish is not a big factor in the thermal process, it may be important for readability.
- If the laser does not induce a color change, a rough surface will require deep engraving to achieve good contrast with the surrounding material.
- A smooth machined surface will yield excellent readability with very shallow engraving.
Material Hardness
For all practical purposes, material hardness is not a factor in laser marking. A laser can mark a hardened steel part just as readily as untempered material.
Reflectivity
Laser light must be absorbed to generate heat. If the material is highly reflective to the laser wavelength, adjustments must be made to the laser power, pulse rate, and beam velocity to achieve a quality mark.
Thermal Conductivity
Highly conductive materials will convey heat away from the point at which the laser is attempting to increase the temperature. The laser parameters will have to be adjusted to compensate for the material’s attempt to heat-sink itself. Aluminum is a classic example: aluminum marking will require more power and/or a slower marking speed.