CO2 laser cutting machine several key technologies are optical, mechanical, electrical integration of the integrated technology. The parameters of the laser beam, the performance and accuracy of the machine and the numerical control system directly affect the efficiency and quality of the laser cutting. Especially for cutting the higher accuracy or thickness of the larger parts, we must master and solve the following key technologies:
1, focus position control technology:
One of the advantages of laser cutting is the high energy density of the beam, generally> 10W / cm2. Since the energy density is proportional to 4 / πd2, the focus spot diameter is as small as possible to produce a narrow slit; the focus spot diameter is also proportional to the focal depth of the lens. The smaller the focal length of the focusing lens, the smaller the spot spot diameter. But the cutting splash, the lens is too close to the workpiece from the lens is easy to damage, so the general high-power CO2 laser cutting industrial applications widely used 5 〃 ~ 7.5 〃 "(127 ~ 190mm) focal length. Actual focus spot diameter of 0.1 ~ 0.4mm For high-quality cutting, the effective depth of focus is also related to the lens diameter and the cut material, for example,CO2 laser cutting machine with a 5 〃 lens cut carbon steel with a focal depth of + 2% of the focal length, ie about 5mm. Relative to the location of the surface of the material being cut is very important. Considering the cutting quality, cutting speed and other factors, in principle <6mm metal material, the focus on the surface;> 6mm carbon steel, the focus on the surface;> 6mm stainless steel , The focus below the surface, the specific size determined by the experiment.
There are three ways to determine the location of the focus in industrial production:
(1) printing method: the cutting head from top to bottom movement, in the plastic plate on the laser beam printing, print the smallest diameter for the focus.
(2) inclined plate method: with the vertical axis at an angle obliquely placed plastic plate to pull the level of the laser beam to find the minimum focus.
(3) blue spark method: remove the nozzle, blow the air, the pulse laser hit the stainless steel plate, so that the cutting head from top to bottom movement, until the blue spark as the focus.
For the cutting machine of the flying optical path, the beam size before focusing is different due to the divergence angle of the beam, the distance between the cutting proximal and the distal end, and the length of the beam before focusing. The larger the diameter of the incident beam, the smaller the diameter of the focal spot. In order to reduce the focus of the beam size caused by changes in the focus of the spot size changes,CO2 laser cutting machine domestic and foreign laser cutting system manufacturers to provide a number of special devices for users to choose:
(1) parallel light pipe. This is a commonly used method, that is, the output of the CO2 laser with a parallel beam tube for beam expansion processing, beam after the beam diameter becomes larger, the divergence angle becomes smaller, so that the cutting work in the vicinity of the proximal and distal The beam size before focusing is close to the same.
(2) The lower axis of a separate moving lens is added to the cutting head, which is two separate parts from the Z axis which controls the nozzle to the surface of the material. When the machine table moves or the optical axis moves, the beam moves from the proximal end to the distal F-axis at the same time, so that the spot diameter of the beam is aligned throughout the processing area.
(3) Control the water pressure of the focusing lens (typically a metal reflex focusing system). If the pre-focus beam size becomes smaller and the focus spot diameter becomes larger kwt_8wt, the automatic control of the water pressure changes the focusing curvature to make the focal spot diameter smaller.
(4) flying optical path cutting machine to increase the x, y direction of the compensation optical path system. That is, when the cutting of the distal end of the optical path increases to make the compensation optical path shortened; otherwise when the cutting near the end of the optical path decreases, so that the compensation optical path to maintain the same optical path length.
2. Cutting and piercing technology:
Any kind of thermal cutting technology, except for a few cases can start from the edge of the board, the general must wear a small hole in the board. Previously in the laser punching machine is a punch with a punch out of a hole, and then use the laser from the hole began to cut. There are two basic methods for punching a laser cutting machine without a punching device:
(1) blasting perforation:
The material is formed into a dimple in the center after continuous laser irradiation, and then the molten material is removed by a coaxial oxygen stream with the laser beam to form a hole. The size of the hole is generally related to the thickness of the blasting perforation average diameter of half of the thickness of the board, so the thicker plate blasting perforation larger diameter, and not round,CO2 laser cutting machine should not be used in the higher parts (such as oil sieve ), Can only be used for waste. In addition, the oxygen pressure used in the perforation is the same as that at the time of cutting, and the splash is large.
(2) pulse perforation:
The use of high-peak power pulse laser to melt or vaporize a small amount of material, commonly used air or nitrogen as auxiliary gas to reduce the expansion due to exothermic oxidation of the hole, the gas pressure than the cutting oxygen pressure is small. Each pulsed laser produces only a small particle jet, which is gradually deepened, so the plate piercing time takes a few seconds. Once the perforation is completed, the auxiliary gas is immediately replaced by oxygen for cutting. This perforation diameter is smaller, the perforation quality is better than the blasting perforation. The laser used for this purpose should not only have a higher output power; more important time and space characteristics of the beam, so the general cross-flow CO2 laser can not meet the requirements of laser cutting. In addition, pulse perforation also need to have a more reliable air control system to achieve the gas type,CO2 laser cutting machine gas pressure switching and perforation time control.
In the case of pulsed perforation, in order to obtain high-quality incision, from the workpiece when the pulse punch to the workpiece constant speed continuous cutting transition technology should be taken seriously. It is theoretically possible to change the cutting conditions of the accelerating section,CO2 laser cutting machine such as focal length, nozzle position, gas pressure, etc., but in fact it is unlikely that the above conditions will be changed due to the time being too short. In industrial production mainly to change the average power of laser approach more realistic, the specific methods are the following three:
(1) change the pulse width;
(2) change the pulse frequency;
(3) change the pulse width and frequency at the same time. The actual results show that the effect of (3) is the best.
3. nozzle design and air flow control technology:
When the laser cutting machine cuts the steel, the oxygen and focused laser beam is fired through the nozzle to the cut material to form an airflow beam. The basic requirement for airflow is that the amount of air entering the incision is large and the velocity is high so that sufficient oxidation allows the exfoliation material to be sufficiently exothermic and that there is sufficient momentum to blow out the molten material. Therefore, in addition to the quality of the beam and its control directly affect the cutting quality,CO2 laser cutting machine the nozzle design and air flow control (such as nozzle pressure, the workpiece in the air flow position, etc.) is also very important factor.