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Common problems and treatment methods in laser cutting

Date time:2016-4-21 9:04:48 Page view:

 Common problems and treatment methods in laser cutting

1.Any kind of thermal cutting technology, in addition to a small number of cases can be from the edge of the board, the general must wear a small hole in the board. Before the laser punching compound machine with a hole punch out first, and then again from the hole at the beginning of laser cutting. Basic method for two kinds of perforation of laser cutting machine without punching device:
Blasting perforation
After the material is irradiated by a continuous laser, a concave hole is formed in the center, and the oxygen flow from the laser beam is quickly removed to form a hole. And sheet thickness is related to the size of the hole and blasting perforation average diameter is half of the plate thickness, so for thick plate blasting perforation diameter larger diameter, should not require higher in precision machining parts, can only be used for waste. In addition, due to the use of oxygen pressure and cutting the same, the splash is larger.
Pulse perforation
Pulsed laser with high peak value is used for melting or vaporization of a small amount of material, air or nitrogen is used as an auxiliary gas to reduce the expansion of the pores due to heat release and the gas pressure is less than the oxygen pressure during the cutting process. 
Each pulse laser produced only a small particle injection, and gradually deepened, so thick plate perforation time takes a few seconds. Once the perforation is completed, the auxiliary gas is changed to oxygen for cutting. The perforation diameter is smaller and the perforation quality is better than that of the blasting hole. The laser used in this system should not only have high output power, but also more important is the time and spatial characteristics of the beam, so the general cross flow CO2 laser can not meet the requirements of laser cutting. In addition, a more reliable pneumatic control system is needed in order to realize the gas type, gas pressure switch and perforation time control.In the case of using pulse perforation, in order to obtain high quality cut, from the workpiece at rest, the pulse perforation to the workpiece constant velocity continuous cutting transition technology should be paid attention to. Theoretically, it is usually possible to change the cutting conditions of the accelerating section, such as the focal length, the position of the nozzle and the gas pressure, but in fact, the possibility of the above conditions is not very much due to the time is too short. In the process of industrial production, the method of changing the average power of laser is used to compare the reality, the specific method is to change the pulse width, change the pulse frequency, and change the pulse width and frequency.
2. cutting holes (diameter and thickness) analysis of deformation
This is because the machine (only for high power laser cutting machine) in machining holes not take the blasting perforation, but with pulse perforation (soft puncture), which makes the laser energy in a very small area is too concentrated, non machining area was burned, cause deformation of the hole, the processing quality is affected. Then we should be in the process, pulse perforation (soft puncture) to blasting perforation (ordinary puncture) way to solve. For small power laser cutting machine is just the opposite, in machining should adopt way pulse perforation to achieve better surface finish.
3.when the laser cutting of low carbon steel, the solution to the work of burr
According to the working principle and design of CO2 laser cutting, and analysis the following reason is caused by machining burrs in the main reason: the laser focus on the position is not correct, need to be adjusted according to the focus position test, offset focus; the laser output power is not enough, need to check the laser generator is normal or not, if the normal, is to observe the effect of laser numerical control output button is correct, adjust the line; the cutting speed is too slow, the need to increase the line speed in operation control; the purity of cutting gas is not enough, need to provide high quality gas cutting work; laser focal shift, need to be adjusted according to the focus position test, offset the focus of the machine running time is too long; the stability, the need to shutdown and restart.
4.Laser cutting of stainless steel and aluminum plated zinc plate, analysis of the causes of burr formation
The factors above, first consider the low carbon steel cutting burr, but not simply accelerate cutting speed, because increased speed sometimes sheet cutting not to wear, this kind of situation in processing aluminized zinc plate is particularly prominent. At this time should be integrated into other factors to consider the machine to solve, such as whether the nozzle to replace, rail movement is not stable, etc..
5.Analysis of laser machine can not cut through
Analysis revealed that several of the following is instable processing of: laser head nozzle selection and processing board does not match the thickness; laser cutting line speed is too fast, need to operate the control lines are reduced speed; in addition, also need to pay special attention to, in the laser cutting machine cutting more than 5mm carbon steel needs to be replaced laser lens focal length of 7.5 ".
6.Method for solving non normal spark in cutting low carbon steel
This situation will affect the cutting section of the parts finish machining quality. At this time, in the case of other parameters are normal, should consider the following: laser head nozzle loss, should be promptly replace the nozzle. In the case of no new nozzle replacement, the cutting work gas pressure should be increased; the nozzle and the laser head are connected at the screw thread. At this point should be immediately suspended cutting, check the laser head connection status, re good thread.
7.Selection of puncture point in laser cutting
Laser cutting the working principle of the laser beam is: in the process, material after the irradiation of laser in the center of the formation a pit, and then by the work flow and laser beam coaxial soon will be molten material removal of the formation of a hole. This hole is similar to line cutting of the thread hole, laser beam on this hole for the processing of opening and starting point of contour cutting, usually under flight light path laser beam walk line direction and the parts to be machined vertically cutting contour tangent direction. Therefore, laser beam in began to penetrate the plate into the cutting contour parts of this period of time, the cutting speed in vector direction will have a great change, namely the direction vector of 90 degrees rotation by vertical to the cutting contour tangent direction turn and cutting contour tangent coincidence, and contour tangent angle is 0 degrees. In this way, the cutting surface of the processed material is relatively rough cut surface, which is mainly in the short time, the laser beam in the direction of the movement of the vector is very fast. Therefore, in the use of laser cutting parts, we should pay attention to this aspect of the situation. , in the design of components of surface cutting fracture no roughness can not to do manual processing in laser cutting programming, to control the software automatically generates the puncture point; however, when design of machining cutting section has higher roughness requirements, note to this problem, usually in series laser cutting program of laser beam starting position be manually adjusted, namely artificial for the puncture point of control. The need to produce the original laser puncture point program moved to the reasonable position of need, to reach the surface precision requirements of the processing parts.