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. The image is engraved by the laser machine line by line, point by point, similar to the way in which an inkjet printer applies ink, but instead of ink being applied, material is removed pixel by pixel 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.