Nowadays, with the rapid development of laser cutting machine manufacturing technology and the continuous improvement of numerical control technology, optical fiber laser processing equipment is rapidly applied in the market of metal plate cutting. With the rapid development of equipment and technology updating, many users encounter many problems when cutting thick plates. According to the market feedback information, the thickness, cutting quality and the price of cutting equipment subdivide the market application group of sheet metal processing and manufacturing, especially the small and medium-sized enterprise users in this field urgently need to cut the thickness range of metal plates, and complete sets of high-power optical fiber laser cutting equipment with good cutting quality. What are the difficulties of laser cutting machine in cutting thick plates?
01 The slit is too narrow, resulting in increased heat loss.
The reduction of 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. The material removal at the bottom of the notch became inconsistent, although the laser penetrated the thick plate, and a large amount of slag was stuck at the bottom. The formation of slag hanging is caused by the low average cutting temperature at the bottom of the incision, which is also due to the large energy loss. In this case, the quality of the incision is usually not high.
02 The diameter of optical fiber laser spot is small, and the focal length depth is limited.
When optical fiber laser cutting metal medium thick plates, although it can maintain a high laser power density in the cutting depth, it is not conducive to cutting and slag discharge because of the small beam diameter and thin cutting seam. This puts forward higher requirements for the mode of fiber laser and the collimation shaping and range of light spot beam, and also brings greater difficulties for the process quality of fiber laser cutting metal medium thick plates.
03 Function and influence of auxiliary gas quality and pressure.
Take oxygen as an example; Oxygen plays an important role in fiber laser cutting carbon steel plates. The laser incident on the surface of the workpiece forms a small hole. When the laser beam moves along the cutting direction, there is oxidized melt around the hole and the cutting seam. The purity and pressure of oxygen have a great impact on laser cutting. If there are many impurities and the pressure is not appropriate, the oxygen can not provide enough energy to the bottom of the incision to form a highly flowing 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 role of the auxiliary gas, and the more difficult it is to maintain the cutting quality. Therefore, it is very important to ensure the proper slit width, auxiliary gas quality, and air pressure control for the cutting quality.
04 The difference of geometric shape makes the cutting quality of inflexion point drop.
When laser cutting thick plates, the inclination angle of the melting front becomes prominent, which will lead to the reduction of the laser absorption coefficient of the material, thus ensuring the cutting quality by increasing the cutting power and reducing the cutting speed. Laser cutting machine will be more widely used in the cutting field because of its high spot conversion rate, high cutting accuracy, flexible processing ability, good cutting quality and adaptability.
