Any thermal cutting technique, except in rare cases where it can start from the edge of the board, generally has to punch a small hole in the board. The early laser stamping compound machine is to punch a hole first, and then use the laser to cut from the hole. With the continuous improvement of laser power and the gradual maturity of technology, laser direct perforation has become the mainstream. So what is laser cutting machine drilling?
(1) Blasting perforation: The material is irradiated by a continuous laser to form a pit in the center, and then the molten material is quickly removed by the coaxial oxygen flow of the laser beam to form a hole. Generally, the size of the hole is half the thickness of the plate thickness and the average diameter of the blasting perforated plate, so the thickness of the plate is larger than the diameter of the blasting perforation, not round, which is not suitable for parts with higher requirements (such as oil screen slit pipes) , can only be used for waste. In addition, since the oxygen pressure of the perforation is the same as that of the cut, the spatter is also larger.
(2) Pulse perforation: Pulse laser peak power is used to melt or vaporize a small amount of material, and air or nitrogen is commonly used as an auxiliary gas due to exothermic oxidation, reducing hole expansion and gas pressure less than oxygen pressure when cutting. Each laser pulse produces only a small jet of particles, which penetrate gradually, so it takes a few seconds for the plate to perforate. Once perforation is complete, the assist gas is replaced by oxygen for cutting. The perforation quality is better than the smaller diameter blasting perforation. The laser used for this purpose should not only have high output power; more importantly, the spatiotemporal characteristics of the beam, so the general cross-flow CO2 laser cannot meet the requirements of laser cutting.
In the case of pulse piercing, in order to obtain high-quality cuts, it is necessary to pay attention to the transition technology from pulse piercing when the workpiece is stationary to constant-speed continuous cutting. In theory, the cutting conditions of the acceleration section, such as focal length, nozzle position, gas pressure, etc., can usually be changed, but in practice, the above conditions are impossible to change due to the short time. 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.