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One of the most important advantages of CNC laser machines (compared to other types of processing machines) is the high versatility and the ability to work with very different materials (including thin and fragile — fabric, leather, paper, film, and rubber). This “omnivory” of laser machines is explained by the very principle of processing. The laser has a non-contact effect on the surface of a workpiece in a very small area (almost equal to the thickness of the beam, i.e. a few millimeters). A high-energy beam instantly heats and vaporizes the material and that is how workpiece cutting is achieved. Sequentially “passing” along the processing route, the laser head performs cutting or curly cutting. Thanks to the software control, the machine can implement the most complex sketch up to the creation of 3D-products!
In addition to the high quality of the cut and the minimum thickness of the seam, non-contact laser treatment has another significant advantage – the complete absence of waste. As mentioned above, during the cutting process, the laser vaporizes all the “extra” material. Therefore, the waste is completely removed by the standard exhaust system of the machine in the form of a gaseous residue.
Processing modes and “firing”
Theoretically, during processing, all the laser energy should be spent on the evaporation of the material in the cutting area. The adjacent layers should not experience any load. This, in particular, allows for laser processing of finished products, including electronic ones (for example, engraving iPhone cases) without the risk of damaging the sensitive “filling”.
However, in practice, the laser machine works with blanks of different densities. Therefore, the “amount of radiation” required for reliable evaporation of the material in the cutting area will also be different. Therefore, without adjusting the processing parameters (laser power, emitter speed, etc.), some materials can “slightly burn”. In addition, when cutting blanks of variable density (due to the heterogeneous internal structure, like leather or plywood), “firing” and even short-term appearance of the flame is possible.
In this case, the inevitable soot rising up can cover the lens of the laser emitter. This degrades the processing parameters and requires more frequent cleaning of the lens, which increases the complexity of machine maintenance.
Air cleaning of the lens
To get rid of the negative effects of smoke and soot, the laser emitter has a built-in blowing system. The head of the laser emitter is a hollow cylindrical body with a conical cover. The screw-on cover holds the focusing lens, allowing you to disassemble the emitter if necessary and remove it for replacement and / or cleaning. The conical nozzle is equipped with a small fitting, which is put on the tube for supplying compressed air.
Compressed air is pumped by a compressor and blows the lens, protecting it from smoke and soot. Blow-off system of the lens also helps to remove products of combustion from the treatment area. Thus, the intensity of blowing is entirely determined by the characteristics of the compressor, and its power has a significant impact on the parameters of processing workpieces.
So, when engraving, you should avoid excessively strong air flow – so that the waste under pressure does not “stick” to the surface of the engraved material. Through cutting, however, requires a powerful stream of air to quickly remove combustion products from the treatment area.
The intensity of the lens blowing can be adjusted by a special screw on the cone of the emitter head. However, the maximum blowing force will still depend on the characteristics of the air compressor (its power). Therefore, the choice of compressor can play an important role in ensuring the quality of workpiece processing on a CNC laser machine.
Selection of air compressor characteristics
As a rule, the standard equipment of a laser machine already assumes the presence of an air compressor. Its characteristics are quite enough for “everyday” tasks. However, if the CNC laser machine is planned for intensive cutting/cutting of materials, it is better to change the compressor to a more powerful one.
It should also be taken into account that with a significant intensity of blowing, the air speed will be seriously affected by the cross section of the supply flexible hose. If you want to increase the airflow, the chosen section of the hose should be small. However the actual mass air consumption will be lower
When using an “oil” compressor (for example, a piston one), it is necessary to use a moisture trap. Otherwise, water or oil vapors can “bake” on the lens and contaminate it. But the task of the air system is to protect the focusing lens from contamination, and not vice versa!
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