The Basics of Laser Engraving – Raster and Vector
Laser engraving is the process of using high powered lasers to melt or vaporize the base material of the workpiece to create a shallow groove. Because it does not involve direct mechanical contact between the tool and the workpiece, laser engraving has become a popular manufacturing technique for producing precision and permanent markings by mechanical manufacturers, electrical manufacturers, artists, and other industries alike.
Advantages of Laser Engraving
- Laser engraving can be applied to a large variety of materials including plastics, wood, aluminum, steel, glass, etc. In many cases, the only tool that needs to be changed is the laser and power supply.
- Mechanical friction and vibration is not present in the workpiece during laser engraving, so fixturing is much easier.
- Precision and reliability after finetuning is on par with or better than CNC machine engraving.
- Very little maintenance and debris cleanup is required after a job is complete.
- Edge of the engraving is not sharp.
Disadvantages of Laser Engraving
- High power consumption and different power requirements for different lasers and materials.
- Heat is a problem and can require large and elaborate cooling systems.
- Safety regulations limit the placement of high powered laser engraving machines.
- Discolored material and evidence of melted base material will be present on deeper engravings due to chemical changes with heat.
CNC laser engraving machines are available in multiple configurations, the most popular including:
Linear X-Y working area with the laser acting on the workpiece in the Z-direction. These machines will either having a stationary working area and moving laser or a moving working area and stationary laser.
A rotary, lathe mechanism used to spin the working area and workpiece as the laser acts in the Z-direction.
Raster is the parallel scanning lines seen on an old projection television screen or computer screen. Modern applications of the word are seen in the inkjet printer industry where the printed image is added line-by-line onto a piece of paper.
Raster engraving operates on the same ideology. The computer-generated bitmap image is composed of individual pixels that are interpreted by the CNC controller of the laser engraving machine. The laser sweeps back and forth across the working area, activating the laser in a very quick on-off pattern to individually engrave each pixel onto the base material of the workpiece.
Raster engraving generally takes much longer than vector engraving.
Vector engraving is exactly as it sounds. The CNC controller passes a series of linear X-axis and Y-axis locations and directions for the laser to position based on the computer-generated image. The laser follows the computer instructions to continuously and more smoothly engrave the workpiece.
Vector engraving is generally used when working with flat surfaces. It is smoother and much quicker than raster engraving because it is not engraving individual pixels and is continuously engraving.
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