Key technology of the tube laser cutting system

10, 2018

by oreelaser

Metal pipes are widely used in aircraft manufacturing, engineering machinery, automobile industry, petrochemical industry, agriculture and animal husbandry machinery and other industries. Due to different application scenarios, metal pipes need to be processed into parts of different shapes and sizes to meet the needs of different industries. Previously we mentioned that advanced laser processing technology is particularly suitable for processing various metal pipes. Nowadays, the tube laser cutting system is developing towards high flexibility and high automation, and finally it can realize the production mode of different materials and small batches. Therefore, to understand and break through the key technology of tube laser cutting system, system equipment suppliers can have a broader development prospect in the field of metal pipe cutting.

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Light guide focusing system


The function of the light guiding focusing system is to direct the beam output from the laser generator to the cutting head of the focusing optical path. For laser-cut tubes, high-quality slits are required to focus the beam with a small spot diameter and high power. This allows the laser generator to perform low-order mode output. During the laser cutting machine is cutting tubes, in order to obtain a relatively small beam focusing diameter, the laser should be a small transverse mode order, preferably a fundamental mode. The cutting head of the laser cutting device is equipped with a focusing lens. After the laser beam is focused by the lens, a small focused spot can be obtained, so that high quality pipe cutting can be performed.


Cutting head trajectory control


In the pipe cutting, the pipe to be processed belongs to the space surface, and the shape is relatively complicated. If the programming is processed by conventional methods, there will be certain difficulties, which requires the operator to select the correct machining path and the appropriate reference point according to the processing requirements. The numerical control system records the feed condition of each axis and the coordinate value of the reference point, and then records the coordinate values of the machining process through the spatial straight line and circular interpolation function of the laser cutting system, and generates a machining program.

 

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Automatic control of laser cutting focus position

How to control the laser cutting focus position is an important factor affecting the cutting quality. One of the key technologies for laser cutting of pipes is the constant measurement of the focus relative to the surface of the workpiece by automatic measuring and control devices. By integrating the control of the laser focus position with the linear axis (XYZ) of the laser processing system, the movement of the laser cutting head is lighter and more flexible, and the position of the focus can be well understood, avoiding collision between the cutting head and cutting pipes or other objects  during processing.


Influence of main process parameters

1.Laser power impact

For a continuous wave output laser generator, the amount of laser power has an important effect on laser cutting. In theory, the greater the laser power of the laser-cutting pipe equipment, the greater the cutting speed, but 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 changes, which affects the focus of the laser beam. In actual machining, we often choose to achieve the highest power density for the focus at less than the maximum power, thus ensuring the efficiency and cutting quality of the entire laser cutting.


2.Cutting speed impact

Laser cutting of the pipe must ensure that the cutting speed is within a certain range to obtain better cutting quality. If the cutting speed is slow, excessive 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 cauterize the surface of the cut, making the surface of the cut rough. When the cutting speed is increased, the average circumferential slit width of the pipe becomes smaller, and the smaller the diameter of the cut pipe, the more obvious the effect. As the cutting speed is increased, the time of laser action is shortened, the total energy absorbed by the pipe is reduced, the temperature at the front end of the pipe is lowered, and the width of the slit is reduced. If the cutting speed is too fast, the pipe may not be cut or cut continuously. Thereby affecting the overall cutting quality.

3.Effect of pipe size


When the tube is laser cut, the characteristics of the tube itself can have a great influence on the processing. For example, the size of the pipe diameter has a significant impact on the processing quality. Through the research on laser-cut thin-walled seamless steel pipe, it is found that the laser cutting pipe equipment keeps increasing the pipe diameter under the condition that the process parameters remain unchanged. The width will also increase

4.Type and pressure of auxiliary gas


When cutting non-metallic and part of metal pipes, compressed air or an inert gas such as nitrogen can be used as an auxiliary gas, and for most metal pipes, a reactive gas such as oxygen can be used. After determining the type of assist gas, it is also important to determine the pressure of the assist gas. When cutting the pipe with a small wall thickness at a higher speed, the pressure of the auxiliary gas should be increased to prevent the slag from appearing in the slit; when the thickness of the cutting pipe wall is large or the cutting speed is slow, the auxiliary gas should be appropriately reduced. The pressure is to prevent the pipe from being cut or cut.


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


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