Raster engraving is the standard process for engraving. This process is the same type of process used by inkjet printers, where a file is printed line by line.
How does this work with a laser?
A raster file is a bitmap, which means it is made up of pixels. In a raster engraving, the image is created in a way quite similar to how an inkjet printer applies ink; line by line and point by point. Rather than ink being applied, however, material is removed by the laser. This is a "bi-directional" process in which engraving is done in alternating fashion in both directions.
During the line-by-line raster engraving process, the speeds of the two axles are very different. The speed is high on the x axle, (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.