In order to make a high quality, permanent mark using TherMark laser marking materials, it is critical to use the correct laser settings which make the materials successfully bond to the substrate. While the “process window” is quite wide for a number of materials being marked, much will depend on the type of laser being used and the settings that have been applied.
 

Type of Laser: The type of laser being used is the primary consideration and the settings between a solid state laser and a CO2 will be entirely different. We recommend a minimum of 30W of power for CO2 lasers, and 10W of power for solid state lasers.  

Power Settings: Laser power is a crucial variable that impacts the bonding process. Too much power will cause the material to vaporize and burn; not enough power will lead to the material failing to bond to the surface. All of the power settings on these pages are expressed in Watts (W). Note that many lasers will express power as a % of the maximum system power so that 20W is listed in the software as being 40% power on a 50W laser.

Speed Settings: The next most important setting is laser speed, this being the speed at which the beam moves across the material while marking. All of the speed settings on these pages are expressed in inches/second (in/sec). Note that many lasers will express speed as a % of the maximum system speed so that 70 in/sec is listed in the software as being 50% speed on a system that has a maximum speed of 140 in/sec. Some laser software programs express the speed settings in metric units (cm/sec). It is important to note the difference between English and metric units and do the proper conversion when translating the settings to different lasers.

Determining the proper settings: While we can recommend basic power and speed settings to get you started (visit your product’s page for downloadable settings charts), it is important for you to determine your optimal settings based on your laser and your substrate. The best method to determine your best settings is to create a power grid on a scrap part, see below for samples
 

Other Important Factors

Beam focus: In all laser marking systems the laser beam is delivered to the substrate through a focusing lens. It is important that the laser beam is correctly focused to make the process work. Some laser systems come with a set of different interchangeable lenses for focusing. Choosing the correct lens for focusing is equally important to achieve high contrast marks. The spot size of the laser beam at the markable substrate directly depends on the focal length of the lens. This in turn directly affects the optimum intensity and speed of marking. In general, shorter focal length lenses generate tighter focuses and require lower intensities and vice versa. Please follow your laser manufacturer’s recommendations and procedures on beam focusing.

Vectoring versus Rastering: Lasers can operate in different modes; the first mode is vectoring, in which the beam is continuously steered around the image in much the same way as a plotter moves. Lasers can also operate in a mode called rastering in which the image is achieved by pulsing dots in much the same way a dot matrix printer works. Both modes will work with TherMark laser marking materials, however, the lasers settings may differ.  

Resolution settings: There will also be settings that determine the resolution of the image in terms of how many dots/inch (DPI) or pulses/inch (PPI) are used. These settings may also influence the marking speed with a higher resolution mark taking significantly longer to complete.  

Continuous Wave (CW) vs. Pulsed solid state lasers: If your solid state laser has both CW and pulsed operating modes, we generally recommend using CW mode.  Contrary to conventional laser marking logic, when bonding laser marking materials rather than direct laser marking, it is better to apply more steady, lower peak power laser energy than sudden, high peak power bursts.  If your laser does not have CW mode, however, you can mimic this mode by setting your Q-Switch frequency to greater than 50 kHz.  An exception to this rule is LMM6018.LF tape which will respond well to pulse mode.  Additionally, if marking speed is a major concern when laser bonding on metal, you may be able to reduce cycle time by running in pulse mode, as well.  This strategy, however, is not recommended for glass, ceramic, or plastic.

Adjusting Your Laser

Testing & Power Grids: The process of establishing the correct laser settings to make TherMark laser marking materials successfully bond can be time consuming because of the number of variables involved. To expedite this process, it is possible to quickly determine the optimum settings using what is known as a “power grid”. In the laser bonding process, the two most important variables are the laser power and the speed with which the beam passes over the material. A power grid is a graphic file constructed to apply different speeds and powers to different parts of the image; this allows the user to test multiple settings with a single pass of the laser, greatly reducing the time taken to find the best setting.

In the picture below, each square in the grid has a different combination of power and speed settings as illustrated in the axes. The Y axis decreases power in increments of 10% from top to bottom (100% power at the top, 30% power at the bottom), while the X axis increases speed in increments of 10% from left to right (10% speed at the left, 100% speed at the right).  

As you can see, optimal marking will only take place when the right amount of energy is transferred by the laser. Section (1) shows that when power is too low and speed is too high there is not enough energy to create a bond.

Likewise, section (2) shows that too much power at a low speed causes the material to be removed, possibly causing damage to the substrate surface.

The ideal “process window” lies in section (3) of the photo. Any of these settings will produce excellent marks on the substrate. Picking a setting in the middle will allow maximum latitude for variability between machines and material. In other cases such as a production environment, the fastest speed possible to create a mark may be preferred.

In summary, when using a TherMark product for the first time on a new substrate, it is advisable to run a power grid on a scrap part in order to determine the optimal settings for your laser/substrate/material/coating combination.