Key technologies of laser cutting system for pipes

1. Light guide focusing system
The function of the light guiding and focusing system is to guide the light beam output by the laser generator to the cutting head of the focusing light path. For laser cutting pipe, to get high-quality slit, it is necessary to focus the beam with small spot diameter and high power. This makes the laser generator perform low order mode output. In order to obtain a smaller beam focusing diameter, the transverse mode order of the laser is smaller, and the basic mode is better. The cutting head of the laser cutting equipment is equipped with a focusing lens. After the laser beam is focused through the lens, a small focusing spot can be obtained, so that high-quality pipe cutting can be carried out.

2. Trajectory control of cutting head
In pipe cutting, the pipe to be processed belongs to spatial curved surface and its shape is complex. It will be difficult to program and process with conventional methods, which requires the operator to select the correct processing path and appropriate reference point according to the processing process requirements, record the feeding of each axis and the coordinate value of the reference point with the NC system, and then use the spatial straight line and arc interpolation function of the laser cutting system, Record the coordinate values of the machining process and generate the machining program.

3. Automatic control of laser cutting focus position
How to control the focus position of laser cutting is an important factor affecting the cutting quality. It is one of the key technologies of laser cutting pipe to keep the vertical direction of the focus relative to the workpiece surface unchanged by automatic measurement and control device. Through the integration of the control of the laser focus position and the linear axis (X-Y-Z) of the laser processing system, the movement of the laser cutting head is more light and flexible, and the position of the focus is well known, avoiding the collision between the cutting head and the cutting pipe or other objects in the processing process.

Influence of main process parameters

1. Influence of optical power
For the continuous wave output laser generator, the laser power will have an important impact on the laser cutting. Theoretically, the greater the laser power of the laser cutting equipment, the greater the cutting speed can be obtained. However, combined with the characteristics of the pipe itself, the maximum cutting power is not the best choice. When the cutting power is increased, the mode of the laser itself also changes, which will affect the focusing of the laser beam. In actual processing, we often choose to make the focus obtain the highest power density when the power is less than the maximum power, so as to ensure the efficiency and cutting quality of the whole laser cutting.

2. Influence of cutting speed
When laser cutting pipes, it is necessary to ensure that the cutting speed is within a certain range in order to obtain better cutting quality. If the cutting speed is slow, too much heat will accumulate on the surface of the pipe, the heat affected zone will become larger, the slit will become wider, and the discharged hot-melt material will burn the notch surface, making the notch surface rough. When the cutting speed is accelerated, the average circumferential slit width of the pipe becomes smaller, and the smaller the pipe diameter is cut, the more obvious this effect is. With the acceleration of cutting speed, the time of laser action is shortened, the total energy absorbed by the pipe becomes less, the temperature at the front end of the pipe decreases, and the slit width decreases. If the cutting speed is too fast, the pipe will not be cut through or cut continuously, thus affecting the whole cutting quality.

3. Influence of pipe diameter
When laser cutting pipe, the characteristics of the pipe itself will also have a great impact on the processing process. For example, the size of the pipe diameter has a significant impact on the processing quality. Through the research on laser cutting of thin-walled seamless steel pipe, it is found that with the constant process parameters of the laser cutting equipment, the pipe diameter will continue to increase and the slit width will also continue to increase.

4. Type and pressure of auxiliary gas
When cutting non-metallic and some metal pipes, compressed air or inert gas (such as nitrogen) can be used as auxiliary gas, while active gas (such as oxygen) can be used for most metal pipes. After determining the type of auxiliary gas, it is very important to determine the pressure of auxiliary gas. When the pipe with small wall thickness is cut at a higher speed, the pressure of auxiliary gas shall be increased to prevent slag from hanging on the cut; When the cutting pipe wall thickness is large or the cutting speed is slow, the pressure of auxiliary gas shall be properly reduced to prevent the pipe from being cut or cut continuously.

When laser cutting pipe, the position of beam focus is also very important. When cutting, the focus position is generally on the surface of the cutting pipe. When the focus is in a good position, the cutting seam is the smallest, the cutting efficiency is the highest, and the cutting effect is the best.

Source: wanshunxing

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