Basically, there are two different modes in laser processing: Raster engraving and vector engraving / vector cutting. These differ in the movement of the axles, and in the parameters used.
Raster engraving is the standard process for engraving. This process is known from inkjet printers, where a file is printed line by line.
How does this work with a laser?
The file to be printed is a bitmap, i.e. made up of pixels. The image to be engraved, represented as a plane, is engraved by the laser machine line by line, point by point. The process is similar to a regular printer, but instead of ink being applied, during raster engraving material is removed layer by layer. This is done bidirectionally, i.e. engraving is done in alternating fashion in both directions.
Due to the line-by-line processing in raster engraving, in this process the speeds of the two axles are very different: High on the x axle, i.e. the axle to which the laser head is attached, and lower by comparison on the y axle.
In raster engraving, the PPI parameter (PPI = pulses per inch) to be selected in the Trotec JobControl® laser software is important, because it controls the density of the laser points. Read more about the parameter definition.
Vector engraving is often referred to as “scoring”. The file to be printed is a graphic that consits of vectors (lines and curves of a geometry), marked as hairlines in the graphics. Therefore, during the handover from the graphics program to the JobControl® laser software the outline is identified as vectors. Vector by vector is traced by the laser and thus engraved.
In vector engraving, the axles move simultaneously, but more slowly than in raster engraving.
The process itself is the same as in laser cutting; the difference is the selected power setting. If a low power setting is chosen, the line is “scored” as engraving; higher power produces a vector cut.
See here for more on the quick determination of optimal laser parameters.
For large-area applications such as filled letters, images, stamps or wood engraving, raster engraving is the appropriate method since it reads pixels.
However, if only thin lines are to be engraved, vector engraving is advantageous and will most likely be faster. In the cutting process, solely vector is used.