Working principle of laser cutting

Laser cutting processing uses invisible beams to replace traditional mechanical knives. It has the characteristics of high precision, fast cutting, not limited to cutting patterns, automatic typesetting to save materials, smooth incision, low processing cost, etc., and will gradually improve or replace the traditional metal cutting process equipment. The mechanical part of the laser cutter head has no contact with the workpiece and will not scratch the surface of the workpiece during operation; The laser cutting speed is fast, the incision is smooth and flat, and there is generally no need for subsequent processing; The cutting heat affected zone is small, the plate deformation is small, and the cutting seam is 0.1mm~0.3mm; The notch is free of mechanical stress and shearing burr; High machining accuracy, good repeatability, and no damage to the material surface; NC programming, can process any plan, can cut the whole board with large format, no need to open a mold, economical and time-saving.

Composition of laser cutting equipment

The laser cutting equipment is mainly composed of laser, light guide system, CNC motion system, automatic height adjusting cutting head, working platform and high-pressure gas blowing system. Many parameters will affect the laser cutting process, some of which depend on the technical performance of the laser and the machine tool, while others are variable. The main parameters of laser cutting are:

Main parameters of laser cutting

【1】 Beam mode

Fundamental mode, also known as Gaussian mode, is the most ideal mode for cutting, which mainly occurs in low-power lasers with power less than 1kW. Multimode is a mixture of higher-order modes. At the same power, the focusing property of multimode is poor and the cutting ability is low. The cutting ability and cutting quality of single-mode laser are better than multimode laser.

How to determine the process parameters of laser cutting?

How to determine the process parameters of laser cutting?

【2】 Laser power

The laser power required for laser cutting mainly depends on the cutting materials, material thickness and cutting speed requirements. Laser power has great influence on cutting thickness, cutting speed and kerf width. Generally, with the increase of laser power, the thickness of the material that can be cut increases, the cutting speed is accelerated, and the width of the incision is also increased.

【3】 Focus position

The focus position has a great influence on the incision width. Generally, the focal point is located about 1/3 of the thickness below the material surface, with the maximum cutting depth and the minimum opening width.

【4】 Focal moment

When cutting thick steel plates, the beam with longer focal moment shall be used to obtain a cutting surface with good perpendicularity. When the focal depth is large, the spot diameter increases, and the power density decreases, which means the cutting speed decreases. To maintain a certain cutting speed, it is necessary to increase the laser power. The light beam with smaller focal length should be used to cut thin plates, so that the light spot diameter is small, the power density is large, and the cutting speed is fast.

【5】 Auxiliary gas

Oxygen is often used as cutting gas for cutting low carbon steel to promote the cutting process by using iron oxygen combustion reaction heat, and the cutting speed is fast, the cutting quality is good, and the cutting without slag can be obtained. The pressure increases, the kinetic energy increases, and the slag discharge capacity increases; The cutting air pressure shall be determined according to the material, plate thickness, cutting speed and cutting surface quality factors.

【6】 Nozzle structure

The structure and shape of the nozzle and the size of the light outlet also affect the quality and efficiency of laser cutting. Different nozzles are selected for different cutting requirements. The commonly used nozzle shapes are: cylindrical, tapered, square, etc. Laser cutting generally adopts coaxial (air flow is concentric with the optical axis) air blowing mode. If the air flow is different from the optical axis, it is easy to generate a lot of splash during cutting. In order to ensure the stability of the cutting process, it is usually necessary to control the distance between the nozzle end face and the workpiece surface, which is generally 0.5~2.0mm, so that the cutting can be carried out smoothly.