Summary of laser cutting machine perforation methods

All thermal cutting techniques of laser cutting machines (except for very few cases) generally must first pierce a small hole in the plate to be cut, and then continue cutting.
1. Blasting and perforation
After the material is irradiated by the 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 larger and not round. It is not suitable for use 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
A pulsed laser with high peak power is used 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 that gradually penetrate deeper, so it takes a few seconds to perforate thick plates. 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, gas pressure and perforation time control.
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 workpiece is stationary to continuous cutting of the workpiece at constant velocity. Theoretically speaking, it is usually possible to change the cutting conditions of the acceleration section, such as the 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.