Knowledge of Laser Cutting Machine

Lasers were first used for cutting as early as the 1970s. When a focused laser beam hits a workpiece, the irradiated area heats up sharply to melt or vaporize the material. Once the laser beam penetrates the workpiece, the cutting process begins: the laser beam moves along the contour while melting the material. And this is laser cutting!

Laser cutting technology process parameters

Laser cutting technology must be familiar to everyone. Laser cutting technology is a processing method that uses a high-energy-density laser beam to accurately cut materials. It is widely used in the processing of metal and non-metal materials. The most common laser cutting equipment is laser cutting machines.

The main process parameters of laser cutting include cutting laser power, cutting speed, cutting thickness and gas flow. Other factors, such as laser beam quality, lens focal length, defocus and nozzle, also have a great influence on laser cutting.

1. Laser power

Laser power is one of the most important parameters of a laser cutting machine. The higher the power, the faster the cutting speed and the greater the cutting thickness. Generally speaking, laser power is the power of the laser.

As for the material properties, if the surface reflectivity of the material is high, then when the laser is irradiated to the surface of the material, more energy will be reflected back instead of being absorbed by the material for cutting. Therefore, in order to ensure sufficient energy for cutting, the power of the laser needs to be increased. Similarly, if the thermal conductivity of the material is good, the heat generated by the laser irradiation will be quickly conducted inside the material, making it difficult for the temperature of the cutting area to rise to a level sufficient for cutting. At this time, the power of the laser also needs to be increased to improve the cutting efficiency. In addition, cutting materials with high melting points also requires larger laser power and power density. Because materials with high melting points require more energy to melt or vaporize them, so as to achieve the purpose of cutting.

2. Cutting speed

Under certain power conditions, when the plate thickness increases, the laser beam needs to penetrate deeper material layers to complete the cutting. Studies have shown that the relationship between cutting speed and surface roughness of the cut is not a simple linear relationship, but presents a U-shaped change trend. This means that for materials of different plate thicknesses and different cutting gas pressure conditions, there is an optimal cutting speed point. When cutting at this speed, the roughness value of the cut surface can be minimized, that is, the cut is the smoothest. Generally speaking, the faster the cutting speed, the greater the power required.

The cutting speed refers to the length that the laser cutting machine can cut per minute. The faster the speed, the higher the efficiency. The cutting speed of the laser cutting machine is related to the type, thickness, hardness, etc. of the material, and is also affected by the laser power and the spot diameter.

3. Cutting thickness

The cutting thickness refers to the thickness of the material that the laser cutting machine can cut. Factors affecting the cutting thickness include:

Equipment power: The higher the power of the equipment, the greater the thickness that can be cut.

Material type: Different materials have different hardness, density and toughness, which affects the cutting thickness.

Cutting technology: Different cutting technologies (such as laser, water jet, plasma) have different maximum cutting thicknesses.

Cutting process parameters: Such as cutting speed, gas pressure, etc. will also affect the cutting thickness.

4. Gas pressure

During the melting cutting process, the laser beam heats the material to the melting temperature, and the gas blown at this time plays the role of blowing away the liquid metal, thereby forming an incision. The gas pressure must be large enough to effectively remove the molten metal and ensure the continuity of the cutting and the clarity of the incision. The gas flow rate is also related to the nozzle form. Different nozzle forms have different effects on the distribution and flow characteristics of the gas, so the applicable gas flow rate will also be different. When selecting the nozzle and setting the gas flow rate, it is necessary to match and optimize according to the specific cutting requirements and material properties.

5. Beam

The beam mode output by the laser is crucial to the cutting effect. Experimental studies have shown that the incision width is almost equal to the laser spot diameter during non-oxygen-assisted cutting. The spot size is proportional to the focal length of the focusing lens, that is, the longer the focal length, the larger the spot; the shorter the focal length, the smaller the spot. However, although a short focal length lens can obtain a smaller spot, its focal depth is also reduced accordingly. The smaller the focal depth, the stricter the distance requirement from the workpiece surface to the lens. The defocus amount has a greater impact on the cutting speed and cutting depth, and must remain unchanged during the cutting process. Generally, the defocus amount uses a negative value, that is, the focal position is placed at a point below the cutting plate surface.

6. Nozzle

The nozzle is an important component that affects the quality and efficiency of laser cutting. Laser cutting generally uses a coaxial (airflow and optical axis concentric) nozzle, and the nozzle outlet diameter should be selected according to the thickness of the cutting material. In addition, the distance from the nozzle to the workpiece surface also has a great influence on the cutting quality. In order to ensure the stability of the cutting process, this distance must remain unchanged.

Laser cutting quality evaluation standard

The application of laser in metal material cutting is already well known, but many people do not know how to judge the quality of processing when using laser cutting machines. In fact, the cutting quality is usually judged from the perspectives of end face roughness, bottom burrs, and slit width.

1. End face roughness

When the laser cuts the material, it is affected by the airflow and feed speed, and the end face will form vertical (or inclined) lines. The deeper the lines, the rougher the end face, and the shallower the lines, the smoother the end face. Roughness not only affects the appearance of the edge, but also affects the friction characteristics. Therefore, the lower the roughness, the higher the cutting quality. By adjusting parameters such as laser power, feed speed, focal length, auxiliary gas type and air pressure, the end face roughness can be continuously optimized.

2. Bottom burr

The principle of laser cutting metal is to vaporize the metal instantly through the high energy of the laser, and blow away the slag on the surface of the workpiece through the auxiliary gas. However, in the actual processing process, factors such as material thickness, insufficient air pressure, and mismatched feed speed will cause some slag to form burrs after cooling and hang on the bottom of the workpiece. At this time, additional deburring work is required, which consumes extra working hours. The burrs and slag at the bottom of the workpiece are very important criteria for judging the cutting quality.

3. Cutting seam width

The cutting seam width is a reflection of the processing accuracy. It usually does not affect the cutting quality. The cutting seam width will only become an important indicator when a particularly precise contour or pattern needs to be formed inside the workpiece. The cutting seam width determines the minimum inner diameter of the contour. The smaller the cutting seam width, the more precise the contour and the smaller the hole diameter can be processed. This is also one of the important advantages of laser cutting replacing plasma cutting.

Laser cutting technology application improvement strategy

In the actual application of laser cutting technology, improving cutting efficiency, improving cutting quality, and reducing cutting costs are one of the things we often need to consider. To improve laser cutting technology to improve production efficiency, cutting quality and reduce costs, we can start from the following aspects:

1. With the advancement of laser technology, the use of higher power lasers can significantly increase the cutting speed, while reducing the heat-affected zone and material deformation, making cutting more efficient and better quality, especially suitable for cutting thicker materials.

2. Reasonably adjust parameters such as laser power, cutting speed, auxiliary gas type and pressure, and the distance between the nozzle and the material, and make fine settings according to specific materials and cutting requirements. Through multiple tests, find the optimal parameter combination to improve cutting efficiency and quality.

3. Through the automatic focusing system, the laser focus position is automatically adjusted according to the material thickness and type to ensure cutting accuracy.

4. Reduce non-cutting time and improve overall operation efficiency by quickly moving the cutting head to the next cutting starting point.

5. Automatically detect the edge and tilt angle of the material, automatically adjust the cutting path, and reduce material waste and preprocessing time.

6. Use nesting software for simulated cutting, plan the simplest cutting path, reduce empty strokes, and improve material utilization and cutting speed.

7. Regularly maintain and service the laser cutting machine, such as replacing wearing parts, cleaning optical components, calibrating equipment, etc., to ensure long-term stable operation of the equipment and maintain optimal cutting performance.

8. Keep the working environment of the laser cutting machine clean, with appropriate temperature and moderate humidity to avoid the impact of dust and excessive humidity on the equipment and cutting effect.

9. Use more advanced control systems and software to improve control accuracy and response speed, and support more complex cutting tasks.

10. Continue to pay attention to new developments in laser technology, such as more efficient laser sources, more advanced optical systems, intelligent software algorithms, etc., to continuously improve cutting capabilities.