Perforation process before laser cutting

Any kind of thermal cutting technology, except in a few cases, which can start from the edge of the board, generally a small hole must be perforated in the board. The early laser punching compound machine first punched a hole, and then used a laser to cut from the hole. With the continuous improvement of laser power and the gradual maturity of technology, direct laser perforation has become the mainstream. So what is the laser cutting machine punching?

(1) Blasting perforation: the material is irradiated with continuous laser to form a pit in its center, and then the molten material is quickly removed to form a hole by the coaxial oxygen stream of the laser beam. Generally, the size of the hole is half of the thickness of the plate and the average diameter of the blasting perforated plate. Therefore, the thickness of the plate is larger than the blasting perforated hole. It is not suitable for higher requirements (such as oil screen pipe). , Can only be used for waste. In addition, since the oxygen pressure of the perforation is the same as that of the cutting, the splash is also larger.

(2) Pulse perforation: Pulse laser peak power is used to melt or evaporate a small amount of material, and air or nitrogen are commonly used auxiliary gases due to exothermic oxidation, reducing pore expansion and gas pressure less than oxygen pressure when cutting. Each laser pulse only produces a small particle jet, which gradually penetrates, so it takes a few seconds for the plate to perforate. Once the perforation is completed, the auxiliary gas is replaced by oxygen for cutting. The perforation quality is better than the blasting perforation with a smaller diameter. The laser used for this purpose must not only have a higher output power; more importantly, the temporal and spatial characteristics of the beam, so the general cross-flow CO2 laser cannot meet the requirements of laser cutting.

In the case of pulse perforation, in order to obtain a high-quality cut, it is necessary to pay attention to the transition technology from pulse perforation when the workpiece is stationary to continuous cutting at a constant speed. Theoretically, it is usually possible to change the cutting conditions of the acceleration section, such as focal length, nozzle position, gas pressure, etc., but in practice, due to the short time, the above conditions cannot be changed. In industrial production, it is more realistic to change the average laser power, that is, to change the pulse width. Change the pulse frequency; the pulse width and frequency are changed at the same time.