There are numerous factors that can impact the cutting quality of a laser pipe cutting machine.
This article analyzes the inherent characteristics of the pipe cutting system, the laser pipe cutting process, and the characteristics of the pipe to be cut, based on theoretical learning and my own experience.
We explore the factors that affect the selection of the chuck of the pipe cutting machine, the cutting system, the supporting parts, the auxiliary gas, and the material and thickness of the pipe to be cut in order to improve the quality of pipe cutting.
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As shown in Figure 1, the laser pipe cutting machine works similarly to the plane laser cutting machine. It focuses a high-density and high-power laser beam onto the surface of the pipe to be cut, rapidly raising the temperature of the laser spot area to the melting or boiling point of the pipe. This process quickly melts or vaporizes the surface of the pipe, completing the cutting work.
As the laser spot moves along the designated cutting route, it interacts with the pipe, creating a slit. Various auxiliary gases are also necessary during the cutting process for slag blowing, cooling, and cutting aid.
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Fig. 1 Laser pipe cutting machine
Influence of inherent characteristics of pipe cutting system on laser cutting quality
Influence of Chuck Selection on Cutting Quality
A high-quality chuck assembly is essential for a good laser pipe cutting machine.
The performance of a laser pipe cutting machine, such as feeding, processing, and blanking, depends heavily on the quality of its chuck assembly.
There are numerous chuck manufacturers on the market, each with its unique features. However, an exceptional chuck assembly must possess the ability to ensure the repeated clamping accuracy. This accuracy is necessary to maintain the pipe’s precision within the controllable range during each clamping process.
Currently, most manufacturers of laser pipe cutting machines prefer products with two or more chucks. The two-chuck, three-chuck, and four-chuck configurations are the prevailing selection trends in the laser pipe cutting machine market.
Influence of Cutting System Selection on Cutting Quality
The pipe cutting machine manufacturer has carefully selected a chuck combination that is ideal for its products, making it equivalent to having perfect hardware. However, for the hardware to operate to its full potential, it requires appropriate software assistance, such as an excellent pipe cutting system.
Popular pipe cutting systems in the market include those developed by enterprises like FScut, Siemens, and Beckhoff.
Since laser pipe cutting machines differ slightly from plane laser cutting machines, two chuck synchronous rotation axes are added to the conventional X, Y, and Z axes. Some laser pipe cutting machine cutting systems may also incorporate additional auxiliary axes to ensure a smooth and seamless pipe cutting process.
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The chuck assembly clamps onto the pipe while the auxiliary shaft ensures that the pipe remains in constant alignment during the cutting rotation. This guarantees that the pipe being cut will not sag throughout the entire cutting process, thereby improving the overall quality of the cut.
Influence of tube cutting parameters on laser cutting quality
Influence of the Selection of Supporting Parts on Cutting Quality
Currently, the standard length of pipes available on the market is 6000mm or longer, which can cause pipes to sag and swing during the clamping and cutting process, significantly impacting the accuracy of the cuts.
To address this issue, manufacturers of laser pipe cutting machines have developed a three-chuck laser pipe cutting machine, and some are even exploring the possibility of a four-chuck laser pipe cutting machine.
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Although three-chuck and four-chuck laser pipe cutting machines offer promising advantages in terms of tail length, cutting accuracy, and automatic feeding and unloading, they come with added complexity and manufacturing costs compared to traditional two-chuck laser pipe cutting machines.
The two-chuck laser pipe cutting machine remains a popular choice among most manufacturers due to its ability to optimize the clamping and cutting process, minimize sagging and rotating swing of pipes, and ensure economic efficiency of the product.
The two-chuck laser pipe cutting machine incorporates material supporting parts between the front and rear chucks, similar to the workbench of a laser cutting machine. These supporting parts allow the pipe to be lifted and followed during the entire clamping and cutting process, thus minimizing sagging and swinging and greatly improving the accuracy of pipe cutting.
Additionally, the two-chuck laser pipe cutting machine offers greater flexibility in matching with automatic feeding and unloading systems, including semi-automatic feeding.
To further improve the accuracy of cutting and blanking for long pipes, a supporting part is usually added near the cutting head, in front of the chuck. This ensures continuous lifting of the pipe’s front end during blanking, minimizing sagging and improving the accuracy of cutting and blanking for long pipes.
Influence of auxiliary gas selection on cutting quality
During the operation of the laser cutting machine, the light spot formed by focusing the laser beam through the lens is irradiated on the material’s surface to be cut. This leads to a rapid increase in temperature, causing the material to reach its melting or boiling point in a short time.
While cutting, the material’s surface may reflect the laser to some extent. To enhance the laser’s absorption on the material surface and increase cutting efficiency, auxiliary gas can be injected.
Auxiliary gases such as oxygen, nitrogen, compressed air, and inert gases are typically used for this purpose.
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Oxygen is commonly used as an auxiliary gas in laser cutting because it promotes the oxidation reaction on the surface of the pipe being cut, which improves cutting efficiency.
When laser cutting power and speed are fixed, increasing oxygen pressure leads to a larger kerf and larger stripes on the cutting section.
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Reducing the oxygen pressure results in a thinner cutting seam, with thin and smooth stripes on the cutting section. However, lowering the pressure to a certain point may cause significant cutting on one side of the pipe while also leaving slag hanging on the other side.
The presence of hanging slag on the opposite side can negatively impact the overall cutting accuracy, and it may become challenging to completely cut through the pipe being worked on.
When cutting high-thickness pipes, special-shaped pipes, or pipes made from unique materials, auxiliary gases such as nitrogen and other inert gases become necessary.
To control costs without compromising overall cutting efficiency, compressed air can be chosen as an auxiliary gas, combined with the metal and physical properties of the pipe being cut.
Influence of physical and chemical properties of the pipe to be cut on the quality of laser cutting
In general, pipes made of different materials exhibit distinct physical and chemical properties that influence their cutting characteristics.
Regarding physical properties, factors such as pipe hardness, melting point, boiling point, and ease of melting can affect the cutting ability of the pipe.
In terms of chemical properties, factors such as flammability, stability, oxidation, combustion support, and others can also significantly differ between pipes, resulting in varying requirements for chuck size, auxiliary gas type and pressure, and laser cutting power.
Typically, thicker pipes necessitate higher laser cutting power for effective cutting.
When dealing with special materials such as aluminum, copper, and stainless steel, as well as pipes with unique shapes (e.g., special-shaped pipes, H beam steel, channel steel, and angle steel), the selection of laser cutting power, auxiliary gas types, and chuck performance needs to be tailored to meet specific requirements.
In addition to laser power and auxiliary gas, supporting parts should also be carefully selected to ensure optimal cutting accuracy when processing elongated, heavy pipe fittings.
Wrap it up
By analyzing the factors that affect the quality of laser cutting pipes discussed above, it is possible to ensure the processing quality of laser cutting pipes to the fullest extent.
Furthermore, this analysis enables laser pipe cutting machine manufacturers to produce advanced machines that can satisfy customer processing requirements while considering market conditions.
For most users of laser pipe cutting machines, selecting a machine with high cost-performance that includes the best laser pipe cutting system and laser pipe cutting process parameters will ensure that the produced pipe products have high processing accuracy.