There are two technical processes for laser cutting machine fiber :
One is that pulsed lasers are suitable for metal materials.
The second is that continuous laser is suitable for non-metallic materials, and the latter is an important application field of laser cutting machine fiber technology.
Several key technologies of laser cutting machine fiber are integrated technology of light, machine and electricity. In the laser cutting machine fiber, the parameters of the laser beam, the performance and accuracy of the machine and the CNC system all directly affect the efficiency and quality of the laser cutting. Especially for parts with higher cutting accuracy or larger thickness, the following key technologies must be mastered and solved:
Focus position control technology.
One of the advantages of laser cutting machine fiber is the high energy density of the beam, generally 10W/cm2. Since the energy density is inversely proportional to the area, the focal spot diameter is as small as possible to produce a narrow slit; at the same time, the focal spot diameter is also proportional to the focal depth of the lens. The smaller the focal depth of the focusing lens, the smaller the focal spot diameter. However, there are spatters in cutting, and the lens is too close to the workpiece to damage the lens. Therefore, the focal length of 5"~7.5" (127~190mm) is widely used in general high-power CO2 laser cutting machine industrial applications. The actual focal spot diameter is 0.1~0.4 mm. For high-quality cutting, the effective focal depth is also related to the lens diameter and the material to be cut. For example, cutting carbon steel with a 5" lens, the focal depth is within +2% of the focal length, that is, about 5mm. So control The position of the focus relative to the surface of the material to be cut is very important. Considering factors such as cutting quality, cutting speed, etc., in principle, 6mm metal materials, the focus is on the surface; 6mm carbon steel, the focus is on the surface; 6mm stainless steel, the focus Below the surface. The specific size is determined by experiment.
There are three easy ways to determine the focal position in industrial production:
(1) Printing method: The cutting head is moved from top to bottom, and laser beam printing is performed on the plastic plate, with the smallest printing diameter as the focus.
(2) Inclined plate method: Use a plastic plate placed obliquely at an angle to the vertical axis to pull it horizontally to find the smallest point of the laser beam as the focus.
(3) Blue spark method: remove the nozzle, blow air, hit the pulse laser on the stainless steel plate, and make the cutting head move from top to bottom until the largest blue spark is the focus.
For laser cutting machine fiber of the flying light path, due to the beam divergence angle, the length of the optical path is different between the near end and the far end, and the beam size before focusing is different. The larger the diameter of the incident beam, the smaller the diameter of the focal spot. In order to reduce the change of the focal spot size caused by the change of the beam size before focusing, the manufacturers of laser cutting systems at home and abroad provide some special devices for users to choose:
(1) Collimator. This is a commonly used method, that is, add a collimator to the output end of the CO2 laser for beam expansion. The beam diameter after beam expansion becomes larger and the divergence angle becomes smaller, so that the proximal and distal ends of the cutting work range The beam size before focusing is nearly the same.
(2) Add an independent lower axis of the moving lens to the cutting head. It and the Z axis that control the distance from the nozzle to the material surface (stand off) are two independent parts. When the machine tool 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 beam spot diameter remains the same in the entire processing area after the beam is focused.
(3) Control the water pressure of the focusing lens (usually a metal reflective focusing system). If the beam size before focusing becomes smaller and the focal spot diameter becomes larger, the water pressure is automatically controlled to change the focus curvature to make the focal spot diameter smaller.
(4) Add x and y direction compensation optical path system on the flying optical path cutting machine. That is, when the optical path at the distal end of the cutting is increased, the compensation optical path is shortened; on the contrary, when the optical path at the proximal end of the cutting is decreased, the compensation optical path is increased to keep the optical path length consistent.
Most organic and inorganic can be cut with laser cutting machine fiber. In the metal processing industry, where industrial manufacturing has a heavy weight, many metal materials, no matter what hardness it has, can be cut without deformation. Common processes for laser cutting machine fiber include vaporization cutting, melting cutting, oxidation melting cutting, and controlled fracture cutting.
- Vaporized cutting
In the laser gasification cutting process, the speed of the material surface temperature rising to the boiling point temperature is so fast that it is enough to avoid melting caused by heat conduction, so part of the material vaporizes into steam and disappears, and part of the material is sprayed from the bottom of the slit by auxiliary gas The flow blows away. In this case, very high laser power is required.
- Metal cutting
In laser melting and cutting, the workpiece is partially melted and the melted material is ejected by airflow. Because the transfer of the material only occurs in its liquid state, the process is called laser melting and cutting.
- Oxidation melting cutting (laser flame cutting)
Melting cutting generally uses inert gas. If it is replaced by oxygen or other active gases, the material is ignited under the irradiation of the laser beam, and a fierce chemical reaction occurs with oxygen to generate another heat source to further heat the material, which is called oxidative melting cutting .
- Control fracture cutting
For brittle materials that are easily damaged by heat, high-speed and controllable cutting is performed by laser beam heating, which is called controlled fracture cutting. The main content of this cutting process is: the laser beam heats a small area of brittle material, causing a large thermal gradient and severe mechanical deformation in this area, causing the material to form cracks. As long as a uniform heating gradient is maintained, the laser beam can guide cracks in any desired direction.
