CO2 laser marking machines are primarily designed for non-metal materials and cannot effectively mark most metal substrates. This limitation comes from three main factors: laser wavelength characteristics, metal material properties, and equipment power configuration.
1. Mismatch Between Laser Wavelength and Metal Absorption
CO2 laser marking machines operate at a wavelength of 10.64 μm in the infrared range. This wavelength is well absorbed by non-metal materials such as plastics, rubber, wood, and glass, allowing marking through thermal effects like surface melting or vaporization.
However, metals generally have very low absorption at 10.64 μm. Among common metals, only steel and iron show limited absorption, and even that is far less efficient than non-metals. Aluminum, copper, gold, and similar metals reflect almost all of the 10.64 μm laser energy, so the beam cannot be converted into enough heat to create a permanent mark.
2. Metal Properties That Work Against Laser Marking
Metals typically have smooth surfaces and high reflectivity in the infrared spectrum, meaning most laser energy is reflected rather than absorbed. Even when a small portion is absorbed, the high thermal conductivity of metal quickly disperses the heat. As a result, the local temperature cannot rise enough to form a durable mark.
Non-metal materials, by contrast, usually have rougher surfaces and lower thermal conductivity. Laser energy is more easily absorbed and concentrated near the surface, producing clear and stable marks.
3. Power Configuration Limitations
CO2 laser marking machines generally use pulsed output with an average power between 10 W and 100 W. Metal processing requires much higher energy density. In theory, shortening the focal length or raising peak power can increase local energy density, but this often means sacrificing processing speed or reducing equipment lifespan. Even with such adjustments, only thin metal sheets or surface coatings can be handled, and the results are not suitable for industrial metal marking.
For users who need to modify existing CO2 systems for limited coated-surface or thin-sheet metal marking, Hansheng Automation can provide custom-machined focusing lens mounts, nozzle adapters, and fixture plates according to specific equipment models. However, for direct and permanent metal marking, a dedicated laser source is still required.
4. Exceptions in Special Cases
If the metal surface is covered with a non-metal coating such as powder coating or paint, a CO2 laser can penetrate the coating and vaporize part of the underlying material to create a visible mark. The result depends heavily on coating thickness and material type, and the metal substrate itself is not directly marked.
With very low power CO2 systems, such as those below 10 W, it may be possible to produce slight oxidation or discoloration on metal surfaces, but the marks are easily worn away and have no real industrial value.
5. Alternative Equipment for Metal Marking
Fiber laser marking machines operate at 1.06 μm, a wavelength that metals absorb much more efficiently. They can process steel, aluminum, copper, and other metals with higher average power, typically from 20 W to 100 W, supporting deep engraving and high-speed marking.
UV laser marking machines use a 355 nm wavelength and work through a cold processing mechanism that breaks chemical bonds on the metal surface with minimal thermal effect. They are suitable for precision metal parts and highly reflective materials such as chrome-plated surfaces.
In summary, CO2 laser marking machines cannot directly mark metal substrates because of poor wavelength absorption, high metal reflectivity and thermal conductivity, and insufficient power density. They remain suitable for non-metal materials and certain metal surface coatings. For effective and permanent metal marking, fiber or UV laser marking systems are the appropriate choice.
