To simulate a solid (usually black) effect within artwork a laser engraving machine will follow a series of parallel lines to ‘fill in’ the solid area in a way similar to what you would shade between outlines on paper with a pencil.
For a plotter format laser engraving machine this software parameter is called ‘DPI’ or ‘resolution’ and for a galvo laser engraving machine it is called ‘Hatch’. For the purpose of this article we’ll call this parameter ‘hatch’.
With a plotter laser the options for adjusting the hatch parameters are very limited. All plotter lasers are constraint to engrave (raster) at one angle, this being zero degrees (left to right) so all plotter lasers only allow for one hatch variable, which is the distance that can be set for the spacing between the hatch lines selected from a list of approximately 6 or so predefined spacing. For example, 1000dpi, 600dpi, 333dpi and so on.
A better designed plotter laser engraver and all galvo laser engravers will allow for the hatch spacing to be set as a unit of measurement, usually down to increments as small as 0.01mm. This provides for a wider range of engraving effects as well as more flexibility to balance the job speed with the output effect and quality of the laser engraving.
Galvo lasers offer the very widest range of hatch parameters because all galvo laser engraving machines can hatch at any angle (a full 360 degrees) and most will have additional controls for the start/stop of the hatch line and also how the laser is control as the motion controls turns out of one hatch line and enters into the next.
The biggest influence on output effect is the hatch spacing and hatch angle. For some jobs a smaller distance between hatch lines will not only increase the resolution of the engraving but it will also influence how the material reacts with the laser. For example, smaller values for hatch spacing can produce on some materials, such as laser engraving stainless steel, a darker effect but add significantly to the process time.
Conversely, a low hatch density (larger hatch spacing) will not only provide for a much faster, lower resolution mark but on some materials it will cause a completely different effect, such as for example a silver effect on stainless steel.
When setting the hatch values it’s also important to consider the material type as well as the characteristics of the lens being used because these factors also determine the maximum achievable resolution.
If using a galvo laser engraving machine, experiment with multiple hatch angles that overlap each other. For some materials this will not only help to darken and deepen the laser engraving but it will also help to make the effect much smoother too.
At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.
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