Laser cutting machine piercing methods

Anyone who uses a laser cutting machine knows that all thermal cutting techniques (except for very few cases) generally must first pierce a small hole in the board to be cut, and then continue cutting. In the past, the laser punching compound machine used a punch to punch a hole first, and then used the laser to start cutting from the small hole. For the laser cutting machine without punching device, there are two ways to perforate:

1.Blasting and perforating 　　

The material is irradiated by the continuous laser to form a pit in the center, and then the molten material is quickly removed by the oxygen stream coaxial with the laser beam to form a hole. Generally, the size of the hole is related to the thickness of the plate. The average diameter of the blasting hole is half of the plate thickness. Therefore, the blasting hole diameter of the thicker plate is larger and not round. It is not suitable to be used on parts with high machining accuracy. On the waste. In addition, since the oxygen pressure used for perforation is the same as that used for cutting, the splash is larger. 　　

2.Pulse perforation 　　

Using a pulsed laser with high peak power to melt or vaporize a small amount of material. Air or nitrogen is often used as an auxiliary gas to reduce the expansion of the hole due to exothermic oxidation. The gas pressure is lower than the oxygen pressure during cutting. Each pulse laser only produces small particle jets, which gradually penetrate deeper, so it takes a few seconds for the thick plate to perforate. Once the perforation is completed, immediately change the auxiliary gas to oxygen for cutting. In this way, the perforation diameter is smaller and the perforation quality is better than blast perforation. For this reason, the laser used should not only have a higher output power; more importantly, the time and space characteristics of the beam, so the general cross-flow CO2 laser cannot meet the requirements of laser cutting. In addition, pulse perforation requires a more reliable gas path control system to realize the switching of gas types and gas pressure and the control of perforation time. 　　

In the case of pulse perforation, in order to improve the quality of the cut, we must pay attention to the transition technology from pulse perforation when the work piece is stationary to continuous cutting of the work piece at constant velocity. Theoretically speaking, it is usually possible to change the cutting conditions of the acceleration section, such as focal length, nozzle position, gas pressure, etc., but in fact, because the time is too short, the possibility of changing the above conditions is very small. At present, in industrial production, we mainly adopt the method of changing the average power of the laser. The specific method is to change the pulse width, change the pulse frequency, and change the pulse width and frequency at the same time.