When the customer uses the laser cutting machine, the cutting effect is not good occasionally. In this case, the cause of the equipment fault is eliminated. How can we solve the problem of poor cutting effect? In fact, the cutting effect is closely related to the process, which mainly includes three process parameters: cutting speed, focus position and auxiliary gas. Next, high-energy laser will teach you how to solve the problem of "how to deal with poor cutting effect of laser cutting machine"!

1. Influence of cutting speed on cutting quality

For a given laser power density and material, the cutting speed conforms to an empirical formula. As long as it is above the pass threshold, the cutting speed of the material is proportional to the laser power density, that is, increasing the power density can improve the cutting speed. The power density referred to here is not only related to the laser output power, but also to the beam quality mode. In addition, the characteristics of the beam focusing system, that is, the size of the focused spot, also have a great impact on laser cutting.

The cutting speed is inversely proportional to the density (specific gravity) and thickness of the material to be cut. When other parameters remain unchanged, the factors to increase the cutting speed are: increase the power (within a certain range, such as 500~2000W); Improve the beam mode (e.g. from high order mode to low order mode to TEM00); Reduce the size of the focus spot, such as using a short focal length lens to focus.

Especially for metal materials, when other process variables are kept constant, the laser cutting speed can have a relative adjustment range and still maintain a satisfactory cutting quality. This adjustment range is slightly wider than that of thick pieces when cutting thin metals. Sometimes, the cutting speed is too slow, which will lead to the ablation surface of the discharged hot melt material, making the cut surface very rough.

2. 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 1.5mm.

3. 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 non-metallic materials and some metal materials, compressed air or inert gas shall be used to treat melting and evaporating materials, while restraining excessive combustion in the cutting area.

For most metal laser cutting, active gas 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, higher gas pressure is required to prevent burrs from sticking slag on the back of the cut. When the material thickness increases or the cutting speed is slow, the gas pressure should be appropriately reduced.

In addition, the practice 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.