1. Piercing technology of metal laser cutting machine
Thermal cutting technology, except that in a few cases, it can start from the edge of the board, generally wear a small hole on the board. Previously, on the laser stamping compound machine, a hole was punched out with a punch, and then cut from the small hole with a laser.
For laser cutting machines without stamping device, there are two basic methods of perforation:
Blasting perforation - the material is irradiated by a continuous laser to form a pit in the center, and then the molten material is quickly thrown away by an 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 large and not round. It is not suitable to be used on the parts with high processing accuracy, but only on the waste. In addition, because the oxygen pressure used for perforation is the same as that used for cutting, the splash is large. Pulse perforation - a small amount of materials are melted or vaporized by pulse laser with peak power. Air or nitrogen is commonly used as the common gas to reduce the hole expansion due to exothermic oxidation. The gas pressure is lower than the oxygen pressure during cutting. Each pulse laser produces only a small particle jet and gradually deepens, so the perforation time of the thick plate takes a few seconds. Once the perforation is completed, the gas is changed into oxygen for cutting. In this way, the perforation diameter is small, and its perforation is similar to blasting perforation. Therefore, the laser used should not only have high output power; What matters is the temporal and spatial characteristics of the beam, so the general cross flow CO2 laser can not meet the requirements of laser cutting. In addition, the pulse perforation must also have a more gas path control system to realize the switching of gas type and gas pressure and the control of perforation time.
2. Analysis of deformation of small holes machined by metal laser cutting machine
This is because the machine tool (only for high-power laser cutting machine) does not adopt the way of blasting perforation when machining small holes, but uses the way of pulse perforation (soft puncture), which makes the laser energy too concentrated in a very small area and scorch the non machining area, resulting in the deformation of holes and affecting the machining quality. At this time, we should change the pulse perforation (soft puncture) mode to blasting perforation (ordinary puncture) mode in the processing program to solve it.
For the laser cutting machine with low power, on the contrary, pulse perforation should be adopted in the small hole processing in order to obtain better surface finish.
