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Everyone 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 laser cutting machines without a punching device, there are two ways to perforate:
1. Blasting perforation
The material is irradiated by 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 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 the parts with higher processing 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 uses high peak power pulsed laser to melt or vaporize a small amount of material. Air or nitrogen is often used as auxiliary gas to reduce the expansion of pores 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, 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. In theory, it is usually possible to change the cutting conditions of the acceleration section, such as focal length, nozzle position, gas pressure, etc., but in reality, the possibility of changing the above conditions is very small because the time is too short. 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.
All thermal cutting techniques of laser cutting machines (except for very few cases) generally must first pierce a small hole in the cut plate before continuing to cut. In the past, a hole was punched out on a laser punching compound machine, and then a laser was used to start cutting from the small hole. For laser cutting machines without punching devices, there are two methods for perforating.
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