Metal tubes are widely used in a variety of industries, including aerospace manufacturing, construction machinery, automotive industry, petrochemicals and agricultural equipment. Different applications require parts of various shapes and sizes to meet the diverse needs of these industries.
Laser processing technology is particularly suitable for working with various types of metal tubes. Tube laser cutting systems are characterized by their high flexibility and automation, allowing the production of small batches of different materials and types of products.
Beam guidance and focusing system
The beam guidance and focusing system directs the laser beam emitted by the generator to the cutting head's focusing optics. For laser tube cutting, achieving high-quality cutting requires a focused laser beam with small diameter and high power, which requires low-order mode output from the laser generator.
To obtain a smaller focused beam diameter during tube cutting, the laser must operate in lower order transverse mode, ideally fundamental mode. The cutting head of the laser cutting equipment is equipped with a focusing lens, which allows the laser beam to be focused on a small spot, enabling high-quality pipe cutting.
Cutting head trajectory control
In pipe cutting, the workpiece is typically a complex spatial curved surface. Traditional programming methods can be challenging, requiring operators to select the correct processing path and appropriate reference points based on process requirements.
The numerical control system records the progress of each axis and the coordinates of the reference points. The linear and circular spatial interpolation functions of the laser cutting system are used to record the coordinates during the process and generate the machining program.
Automatic Control of Laser Cutting Focal Position
Controlling the position of the laser cutting focal point is a critical factor affecting cutting quality. One of the main technologies in laser tube cutting is to maintain the focus position perpendicular to the surface of the part through automatic measuring and control devices.
With integrated control of the position of the laser focus and the linear axes (XYZ) of the laser processing system, the movement of the laser cutting head becomes more agile and precise, avoiding collisions with the tube to be cut or other objects during processing.
Influence of main process parameters
- Effect of laser power
For continuous wave laser generators, laser power significantly impacts the cutting process. In theory, higher laser power allows for higher cutting speeds.
However, considering the specific characteristics of the tubes, maximum cutting power is not always the best choice. As the cutting power increases, the laser mode also changes, affecting the focus of the laser beam.
In practice, we often opt for a power setting below the maximum to guarantee the highest power density at the focal point, thus guaranteeing efficiency and quality in laser cutting.
- Effect of cutting speed
To obtain good cutting quality, the cutting speed must be within a certain range. If the speed is too slow, excessive heat builds up on the pipe surface, enlarging the heat-affected zone, widening the cut, and burning the cut edges, resulting in a rough surface.
Increasing speed reduces the average width of cut around the circumference of the pipe, and this effect is more pronounced with smaller pipe diameters.
As the speed increases, the laser interaction time decreases, reducing the total energy absorbed by the tube, lowering the temperature in front of the tube, and narrowing the kerf width. If the speed is too fast, incomplete cuts or breakage may occur, affecting the overall quality of the cut.
- Effect of tube diameter
When laser cutting tubes, the characteristics of the tubes themselves greatly influence the process. For example, the diameter size of a circular pipe significantly affects the cutting quality.
Studies on laser cutting of thin-walled seamless steel tubes have shown that, with constant process parameters, an increase in tube diameter results in a wider cut.
- Auxiliary gas type and pressure
For cutting non-metallic pipes and some metallic pipes, compressed air or inert gases (such as nitrogen) can be used as auxiliary gases, while for most metallic pipes, active gases (such as oxygen) are preferable.
After selecting the type of auxiliary gas, determining its pressure is also crucial. High pressure is required when cutting thin-walled pipes at high speeds to prevent slag from adhering to the cut edges.
Conversely, when cutting thicker walls or at slower speeds, the auxiliary gas pressure must be reduced to avoid incomplete cuts. The position of the focal point of the laser beam while cutting the tube is also vital.
The focal point should generally be on the surface of the pipe being cut; When in the ideal position, cutting is minimized, cutting efficiency is maximized and the best cutting results are achieved.
