As its name suggests very clearly, laser engraving is the art of engraving or marking objects using one or multiple lasers. Considering the preciseness that is required with the engraving, the whole process is quite complex and technical, which often requires a computer. Therefore, as desired, the final engravings are done extremely precise at a very high rate.
Most of the laser engraving done today is conducted by what is known as a laser engraving machine. This machine has three main parts to it: a laser, a surface, and a controller to control the engravings.
There are generally three types of engraving machines. The most widely used of them all is the X-Y table, which is when the surface is stationed and the laser moves in X and Y coordinates to draw the vector. However, there are exceptions with both of them. For example, the work piece (surface) might move in a Y direction while the laser moves in an X direction. Then, another genre of the engraving machines is a machine specifically for cylindrical surfaces. For these odd shaped surfaces, the laser navigates in a helix form to completely cover the cylindrical surface while turning on and off to produce the correct image on a raster basis. The third type is where both the surface and the laser are stationed. Then, the galvo mirrors at various angles will reflect the laser beam onto the surface of the workpiece to precisely engrave. This can be done in both raster and vector mode.
In all the three types of laser engraving, laser very efficiently removes a slight surface of the workpiece, as nearly all of the light energy (of the laser) is converted to heat energy. This highly focused and collimated beam heats up the machine rather rapidly, thus, an excessive amount of cooling systems are used to maintain the normal temperature of the machine during the engraving process. Sometimes though, the laser is pulsed to decrease an excessive amount of heating at one interval.
All the different patterns during the laser engraving process are done through a pre-programmed setting controlled by the controller. The key to laser engraving is removing an equal amount of material every time. Thus, crossing over a path already gone over by the laser should never happen. The speed of the engraving or the tracing is also carefully done along with intensity and the spread of the beam.
For complex designs requiring a high degree of precision, laser tables are used. Also known as the X-Y table, it is a special equipment that guides the laser beam in heating the surface more precisely. The setup is composed of a laser that consistently comes out parallel to one axis of the table. The axis is aimed at a mirror on the other end of the rail. Then, the beam is reflected off the mirror on the other side angled right at 45 degrees, which allows the beam to travel right on the path along the length of the rail. Finally, the beam is mirrored down by another mirror on a trolley, which directs the laser perpendicular to the original axis. These reflections allow the laser to be in two degrees of freedom, allowing a vertical and a horizontal engraving to occur at once.
There is also the flat table or drum engraving devices. This is when the laser beam directs most of its energy so that the surface is engraved at a correct depth. This allows a set amount of the material to be removed every time, allowing a uniform engraving. Usually this method is conducted with flat surfaces having hardly any height changes. For surfaces with varying heights, mechanisms such as the dynamic auto focus system is applied. This is when the laser's parameters are constantly changed (real time changes) allowing the beam to adapt to the changes in the material. However, these mechanisms require work with what is known as pilot beams or pilot lasers, such as ultrasound, infrared, and visible light.
Materials That Can Be Laser Engraved
There are only certain types of materials where laser engraving can successfully be done.
- Natural materials such as lumer
- Metal, including coated metals
- Stone and glass