What is laser etching?
Laser etching or laser engraving refers to the process of marking or engraving on the surface of materials made o metal, polymers or alloys. Laser etching does not involve the use of ink or contact tools for marking the material surface. This eliminates the need of regularly replacing the metal tips that gets worn out or blunt after repetitive usage.
Laser etching machine components
Laser etching machines have three major components:
Laser: The laser is the main tool for marking or engraving different patterns on the surface of the given material. The points on the surface of the material, that are engraved by the laser beam lies on/near the focal point of the laser optical system. The area that does not fall near the focal point does not get affected by the laser beam. The energy provided by the laser heats up the material and eventually vaporizes or flakes off the material from the surface.
Controller: The controller is used for determining the direction, intensity of laser beam, speed of movement, and spread of the laser beam targeted at the surface of the material. The controller can be programmed to enable the laser to follow a certain desired engraving pattern. The laser beam intensity and speed is carefully regulated by the controller to maintain consistency in depth of the engraving. The appropriate power of the laser beam for different materials is also determined by the controller.
Surface: The surface provides a platform for placing the material for the laser to act on. This surface does not require an enclosing boundary or any holding equipment to hold the material in place because of the laser pointer’s accuracy. The controller is programmed to allow the laser to follow a certain path only.
Apart from these main components, every laser etching setup uses a vacuum pump or a blower to remove the flakes or debris off the surface of the material after the engraving process. Vacuum pumps also help in removing the noxious fumes and smoke generated during the process.
What are the types of laser etching machines?
Laser etching/engraving machines are generally found in three different types:
The X-Y type laser machines are the most commonly used laser etching machines. These machines generally have a stationary workpiece or surface and a mobile laser system. The laser is free to move in two dimensions i.e. in the form of vectors. In some machines, the laser system is fixed and the surface is mobile. In few machines the laser system moves in one axis dimension and the surface moves in the other.
The cylindrical type of laser engraving machines involves the use of cylindrical workpieces that are mounted by flat surfaces and the laser transverses a fine helix effectively. In these laser etching systems, the on-off laser pulsing is used for generating the required raster image.
A third type of laser engraving machines are also available in which both the workpiece and the laser system is fixed or stationary. In these machines, galvo mirrors are used for moving the laser beam across the surface of the material to engrave a pattern. This technique of laser etching is capable of working in either vector or raster mode.
What are the applications of laser etching?
Direct laser engraving of flexographic printing cylinders and plates
Carbon dioxide lasers were initially used for ablating and marking patterns on the surface of rubber plates without the use o ink and contact tools. Carbon dioxide lasers were later replaced by fiber lasers for engraving flexographic plates. These lasers provided an enhanced engraving quality. Direct laser etching or engraving is now a commonly used printing form for flexographic plates.
Direct photopolymer laser engraving
In this process, a photopolymer plate material with a mask layer on the material surface scans the given electronically generated image and the infrared laser imaging head helps in ablating the mask to show the uncured engraved polymer. Then an ultraviolet exposure is used for forming the image through the mask. The digital plate is then processed in a manner similar to flexographic printing. This method has become widely popular for labeling plates.
Laser engraving of anilox rolls
Carbon dioxide lasers were used for engraving a desired cell pattern on a polished ceramic surface. Later, the carbon dioxide lasers were switched with YAG lasers as the latter provided a more focused beam allowing fine pattern engraving more effectively. Nowadays, fiber lasers have become more common for this process because they allow rapid switching of multiple laser beams.
Sub-surface laser engraving (SSLE)
Sub-surface laser engraving or SSLE refers to the technique of marking or engraving an image on a transparent solid material with the help of laser beams. This process involves the focusing of laser beams beneath the surface of the material for producing fine fractures. SSLE uses diode pumped solid state lasers or DPSS for engraving. Such engravings are mostly done on high-quality optical crystals.
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