The laser cutting machine needs to be equipped with auxiliary gases, mainly oxygen, nitrogen and air. When processing the workpiece, the optical fiber laser cutter will be irradiated by the laser focus, and the irradiated area will melt and vaporize instantaneously, and then move the irradiation position of the spot through the CNC equipment system to achieve automatic cutting.
1. Compressed air.
Air is suitable for cutting aluminum sheet and galvanized steel sheet. To some extent, it can reduce oxide film and save costs. Generally, it is used when the cutting plate is relatively thick and the requirements for cutting end face are not too high.
2. Nitrogen.
Nitrogen is an inert gas, which can prevent oxidation and combustion of the cutting end of the product during the cutting process (it is easy to happen when the plate is very thick. Nitrogen can be selected for products with high requirements on the cutting end but not requiring cutting). It needs to be exposed to the outside.
3. Oxygen.
Oxygen mainly plays the role of combustion supporting, which can make the cutting speed faster and the cutting thickness thicker. Oxygen is suitable for thick plate cutting, high-speed cutting and thin plate cutting. For example, some large carbon steel plates and some thick carbon steel plate structural parts can use oxygen.
Increasing the air pressure can increase the cutting speed, but after reaching the set value, continuing to increase the air pressure will reduce the cutting speed. At high auxiliary air pressure, the reason for the reduction of cutting speed may be that the high air volume and the cooling effect of the action area are enhanced, or the interference of intermittent air shock wave flows to the cooling of the laser action area.
The non-uniformity of the pressure and temperature in the air flow will lead to the change of the density of the air flow field. This density gradient causes the refractive index in the field to change, thus focusing the beam energy, causing refocusing or beam divergence. If the beam diverges too much, this interference will affect the melting efficiency, and sometimes may change the mode structure, leading to a decline in cutting quality. The light spot is too large, which may even lead to serious consequences, resulting in the inability to effectively perform cutting.
Application of auxiliary gas:
1. Compressed air: It is widely used in the processing of some sheet metal chassis, cabinets and other products.
2. Nitrogen: process some parts for decoration industry, aerospace, etc;
The laser cutting machine uses different auxiliary gases to cut different materials. The pressure and required flow rate of the auxiliary gas vary with the thickness of the cutting material.