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Variables to Consider

 

The process window for creating an excellent mark with TherMark laser marking materials ranges from quite easy to challenging depending on a number of variables which can affect the marking process. The more these variables are recognized, understood, and adjusted for, the better your marks will be.

 

Laser variation
Despite lasers being specified as having a specific output power, the reality is that many lasers are not actually delivering the exact power advertised. This variation is not normally extreme, but some lasers vary as much as 5-10% from what their manufacturers describe. In most cases this is easily adjusted for by increasing or decreasing the power of the laser during the marking process. However, for our customers with lower power lasers, this can be a potential problem if their laser cannot deliver the minimum power needed to create a mark. For more information on required power for marking, please see our section on
Laser Settings.

 

The laser beam in laser marking systems is focused through a lens which focuses the beam on to the surface to be marked. The focal spot size of the laser beam directly relates to the energy density of the beam: the tighter the focus, the higher the energy density and vice versa. Different lenses will focus the same beam differently resulting in a large variation of spot sizes from laser to laser, and thus of energy density, for the same output powers. Moreover, the laser beam quality (M2 value in technical terms) will strongly affect its focusing properties, the focal spot size, and consequently the energy density at the focus. Hence, proper adjustment of laser settings will be needed for successful marking.

 

Tip: It is a good idea always to do a test power grid on a scrap part before moving to production pieces. This will enable you to determine your own optimal settings for your laser. For more information on power grids, click here.

 

Substrate variation
Variation in substrate composition is something to be aware of when marking metals with TherMark laser marking materials. If your parts to be marked do not have a consistent metallurgy or composition they may each react differently with our materials. When doing large production runs it is important to use parts that have the same composition in order to achieve consistent marks.

 

Tip: When changing suppliers, make sure to test new parts and adjust your laser settings as appropriate.

 

Thermal conductivity of the substrate
The optimum marking settings will also depend on the thermal conductivity of the substrate being marked. The reason for this is that to successfully bond to the substrate the laser beam should heat the frit in the ink to certain high temperatures locally. When marking materials with high thermal conductivity, heat can dissipate due to thermal conduction. Therefore, higher settings may be required. With the same token, different materials have different heat capacities, which is the amount of energy required to increase the temperature by one degree. These two parameters combined will define the optimum settings required for each substrate. Usually metals require higher powers than plastics or glass materials.

 

Substrate thickness
The above mentioned parameters of thermal conductivity and heat capacity directly relate to the shape and volume of the object being marked. Thin substrates such as thin sheets of metals, for example, are much easier to heat up than bulk metals and may require slightly lower powers for marking. This is also a relevant issue when marking plated materials. For example, one may want to mark a chrome plated brass object, where the mark should be bonded to the thin layer of chrome plating. In this case, the power settings for laser marking should be lower than in a case of marking a bulk chrome so as not to damage the thin layer.