As we all know, when cutting thick metal plates with laser cutting machine, it is often necessary to punch on the plate first, except that the knife can be cut from the edge of the plate in a few cases. In the early days, a hole was punched out with a punch on the laser stamping compound machine, and then cut from the small hole with a laser. With the continuous improvement of laser power and the gradual maturity of technology, laser direct perforation has become the mainstream.
Laser perforation can be divided into blasting perforation and pulse perforation.
Blasting perforation
After the material is irradiated by continuous laser, a pit is formed in the center, and then the molten material is quickly removed by the oxygen flow coaxial with the laser beam to form a hole. Generally, the size of the hole is related to the plate thickness. The average diameter of the blasting hole is half of the plate thickness. Therefore, the blasting hole diameter of the thicker plate is large and not round. It is not suitable to be used on the parts with higher requirements (such as oil screen seam pipe), but only on the waste. In addition, because the oxygen pressure used for perforation is the same as that used for cutting, the splash is large.
Pulse perforation
In order to obtain better cutting quality, pulse perforation is generally used in fiber laser cutting. Pulse perforation uses pulse laser with peak power to melt or vaporize a small amount of materials. Air or nitrogen is often used as auxiliary gas to reduce the hole expansion due to exothermic oxidation. The gas pressure is lower than the oxygen pressure during cutting. Each pulse laser only produces small particle jet, which goes deep step by step. In this way, the perforation diameter is small, the sprayed slag is less, and the perforation quality is better than that of blasting perforation. After the perforation is completed, immediately replace the auxiliary gas with oxygen for cutting, which can make the cutting start more stable.
Perforation method guidance
1. The peak power shall be as high as possible to improve the perforation efficiency;
2. Ensure that the laser spot will not hit the nozzle, and the perforation focus will be properly reduced;
3. The air pressure of oxygen perforation is equal to that of cutting;
4. Add light stop and air blowing between multi-stage perforations, non explosive holes.
