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Laser Settings
Influence of laser settings on the marking’s resolution in dots per inch (dpi)

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How the laser setting affects the result of the mark
Four main factors determine how good the overall result of the laser marking will be:
  • Speed
  • Frequency
  • Focus
  • Laser power
The homogeneity of the laser mark depends largely on the distribution of the additives in the matrix (the plastic or the powder coating). Contrast, speed and resolution of the laser marking are determined by the laser parameter settings, because they strongly control the darkness, size and spacing/overlapping of the individual dots in plastics and their visual appearance.

Dot darkness
In general, a laser marking is achieved through the "amount of energy per pulse per surface area" – also called energy density. The higher the energy density is, the greater its effect on the plastic. You decide how dark the single dot is.

This darkness is increased by
  • Increasing the power setting of the laser – just as dimming a light source can vary the intensity of a laser 
  • Increasing the overlap of subsequent dots – if the energy density becomes too high, other phenomena (foaming, evaporation) can occur and decrease the dot darkness
  • Frequency – the higher the frequency, the more dots that are set and the higher the energy density
The best laser settings can be determined using a ramp on which the length of the test workpiece (white) reaches from above to below the laser’s focus (red dashed line).
Dot size 
The size of each marking dot is determined by the spot size of the laser beam. Since the laser beam also heats the surrounding material, the marked dot size may be slightly larger than its own diameter. The type of laser determines the minimal spot size of a laser beam. Starting with this minimum, the spot size can be increased by changing the relative focal point position (z axis). However, the energy density becomes less – and thus possibly the dot darkness. Dot size and dot darkness therefore compete – with an uncertain effect on the contrast.

Dot density per inch (dots per inch = dpi)
The space between two dots is the result of two settings that are independent of each other:
  • Frequency: The number of laser pulses – number of dots per second
  • Marking speed: The linear speed (mm/sec) at which the laser beam moves across the part’s surface
Influence of laser settings on the marking’s resolution in dots per inch (dpi)
Laser parameters
The following laser setting possibilities determine the marked dots in the plastic or the powder coating with respect to their darkness, density and size:
  • Power: The power of the laser beam corresponds to the energy per pulse. For laser marking plastics or powder coated surfaces, a pulsed laser beam generally is used. High pulse power is generated by storing average power for a certain period of time and then releasing it as a very short pulse.
  • Frequency: The frequency equals the number of pulses per second. The lower the number of pulses per second, the greater the peak pulse power and its effect on the plastic or the powder coating.
  • Spot size of the laser beam: The spot size of the laser determines both the line width and the power of the marking process. It is regulated by changing the focal distance or the type of plane field lens used. Increasing the point size widens the line and lowers the energy density.
  • Marking speed: The speed at which the laser beam moves over the plastic. It should be adjusted to the frequency and number of dots per inch (dots per inch = dpi) that the laser marks on the plastic or powder coating. It is limited by the speed at which the laser beam is deflected.
  • Line distance: Lines can influence one another by heat transfer – depending on their distance and the types of polymers used. The contrast of the line may be improved by repeated marking cycles.
You will find more information about optimizing your laser marking, under Polymers & Additives.
Are you interested in specific information about our Iriotec® 8000 products or would like technical application advice? Please use the menu item on the right to contact us .