Now, with the rapid development of laser cutting machine manufacturing technology and the continuous improvement of the level of CNC technology, fiber laser cutting equipment is widely used in the field of sheet metal cutting due to its high photoelectric conversion rate, high cutting precision, flexible processing ability, good cutting quality and adaptability. The development of equipment and technology updates are getting faster and faster, and many users encounter some problems when cutting thick plates. So what are the difficulties of laser cutting machines when cutting thick plates?
1. The slit is too narrow, resulting in increased heat loss
The reduction in cutting speed increases the heat loss in the cutting area. The main form of heat loss is heat conduction. The greater the thickness, the greater the heat conduction loss and the lower the cutting speed. Material removal at the bottom of the cut became inconsistent. Although the laser penetrates the thick plate, a large amount of slag will stick to the bottom. The formation of slag is caused by the low average cutting temperature at the bottom of the cut, which is due to the large energy loss. In this case, the cutting quality is usually not good.
2. The diameter of the fiber laser spot is small, and the depth of focus is limited
When the fiber laser cutting machine cuts metal medium and thick plates, although it has a high laser power density, it is not conducive to slag discharge due to the small beam diameter and thin slit. This puts forward higher requirements for the mode of fiber laser, spot collimation, etc, and also brings greater difficulty to the cutting quality of medium and thick metal plates.
3. The influence of the quality and air pressure of auxiliary gas
Take oxygen as an example; oxygen plays a very important role in cutting medium and thick carbon steel sheets. The laser is incident on the surface of the workpiece to form small holes. When the laser beam moves along the cutting direction, there are oxidized melts around the small holes and the slit. The purity and pressure of oxygen have a great influence on laser cutting: oxygen with a lot of impurities and inappropriate air pressure cannot provide enough energy to the bottom of the cut, which will form a highly fluid melt, thus reducing the cutting quality and cutting speed By measuring the quality and pressure of the auxiliary gas at different slit positions, it is found that the narrower the slit, the worse the effect of the auxiliary gas, and the more difficult it is to maintain the cutting quality. Therefore, ensuring the appropriate slit width, auxiliary gas quality and air pressure control has a very important effect on the cutting quality.
4. Different geometries cause poor cutting quality at the inflection point
When cutting thick plates, the inclination angle of the melting front becomes prominent, which will lead to the reduction of the material’s absorption of laser light, thereby ensuring the cutting quality by increasing the cutting power and reducing the cutting speed.
Below is a thick plates(30mm aluminum)cutted by retrofited 6kw fiber laser cutting. Cutting quality is good. If you are intrested in upgrading your old CO2 laser cutting machine to fiber lasers, welcome to contact us, we are experts in this field.
If you want to know more skills to improve cutting quality, you can also check our previous articles.
