Nowadays, high-power laser cutting machines have been gradually popularized, but for operators, if they want to have better cutting effect and higher section quality, they must understand the three key points about laser cutting machines. According to years of technical experience of high-energy lasers, let's popularize the impact of the three key points on cutting quality.

1. Effect of focus position adjustment on cutting quality

Because the laser power density has a great influence on the cutting speed, the selection of lens focal length is an important issue. After the laser beam is focused, the spot size is proportional to the focal length of the lens. After the beam is focused by the short focal length lens, the spot size is very small, and the power density at the focal point is very high, which is favorable for material cutting; However, its disadvantages are that the focal depth is very short and the adjustment margin is small, which is generally suitable for high-speed cutting of thin materials. As long focal length lens has wide focal depth, it is more suitable for cutting thick workpieces as long as it has sufficient power density.

After determining which focal length lens to use, the relative position of the focus and the workpiece surface is particularly important to ensure the cutting quality. Because of the high power density at the focus, in most cases, the focus position is just on the workpiece surface or slightly below the surface when cutting. In the whole cutting process, it is an important condition to ensure that the relative position between the focus and the workpiece is constant to obtain stable cutting quality. Sometimes, the lens is heated due to poor cooling during operation, resulting in a change in focal length, which requires timely adjustment of the focus position.

When the focus is in a better position, the kerf is smaller, the efficiency is higher, and better cutting speed can obtain better cutting results.

In most applications, the beam focus is adjusted just below the nozzle. The distance between the nozzle and the workpiece surface is generally about 1.0mm.

2. Influence of auxiliary gas pressure on cutting quality

Generally, auxiliary gas is required for material cutting, and the problem mainly involves the type and pressure of auxiliary gas. Generally, the auxiliary gas and laser beam are ejected coaxially to protect the lens from contamination and blow away the slag at the bottom of the cutting area. For metal materials, use compressed air or inert gas to deal with melted and evaporated materials while restraining excessive combustion in the cutting area.

For most metal laser cutting, oxygen is used to form oxidation exothermic reaction with hot metal. This additional heat can increase the cutting speed by 1/3~1/2.

On the premise of ensuring the auxiliary gas, the gas pressure is a very important factor. When cutting thin materials at high speed, high gas pressure is required to prevent slag sticking on the back of the cut (hot slag will damage the cut edge when it hits the workpiece).

The practice of laser cutting shows that when the auxiliary gas is oxygen, its purity has a significant impact on the cutting quality. A 2% reduction in oxygen purity will reduce the cutting speed by 50% and cause a significant deterioration in the quality of the incision.

3. Influence of laser output power on cutting quality

For continuous wave output laser, laser power and mode will have an important impact on cutting. In actual operation, larger power is often set to obtain higher cutting speed, or to cut thicker materials. However, the beam mode (the distribution of beam energy on the cross section) is sometimes more important, and when the output power is increased, the mode often becomes slightly worse. It is often found that, when the power is less than the high power, a higher power density is obtained at the focus, and a better cutting quality is obtained. During the whole effective working life of the laser, the mode is not consistent. The condition of the optical elements, the subtle change of the laser working gas mixture and the flow fluctuation will affect the mode mechanism.

To sum up, although the factors affecting laser cutting are relatively complex, pay attention to the above three points. The focus position, auxiliary gas pressure, laser power and mode structure can cut a satisfactory workpiece. During the cutting process, if the cutting quality is found to be significantly worse, first check the factors discussed above and timely adjust them.