These are the basics of laser cutting that you must master!

Release Date：2025/03/28

Lasers were first used for cutting as early as the 1970s. In modern industrial production, laser cutting is more widely used in sheet metal, plastics, glass, ceramics, semiconductors, textiles, wood and paper processing and other materials.

laser cutting

When the focused laser beam hits the workpiece, the irradiated area heats up dramatically to melt or vaporize the material. Once the laser beam penetrates the workpiece, the cutting process begins: the laser beam moves along the contour lines while melting the material. The molten material is usually blown away from the kerf by a jet of air, leaving a narrow slit between the cut part and the plate holder that is almost as wide as the focused laser beam.

flame cutting

Flame cutting is a standard process employed when cutting mild steel, using oxygen as the cutting gas. Oxygen is pressurized to up to 6 bar and blown into the cut. There, the heated metal reacts with the oxygen: it begins to burn and oxidize. The chemical reaction releases a large amount of energy (up to five times the energy of the laser) which assists the laser beam in cutting.

Figure 1 The laser beam melts the workpiece and the cutting gas blows away the molten material and slag in the kerf.

Melt Cutting

Melt cutting is another standard process used when cutting metals. It can also be used to cut other fusible materials such as ceramics.

Compressed air cutting

Compressed air can also be used to cut thin plates. Air pressurized to 5-6 bar is sufficient to blow away the molten metal in the cut. Since nearly 80% of the air is nitrogen, compressed air cutting is essentially a melting cut.

Plasma-assisted cutting

If the parameters are properly selected, a plasma cloud will appear in the plasma-assisted fusion cutting kerf. The plasma cloud consists of ionized metal vapor and ionized cutting gas. The plasma cloud absorbs the energy of the CO2 laser and converts it into the workpiece so that more energy is coupled to the workpiece and the material will melt faster, resulting in a faster cutting speed. For this reason, this cutting process is also called high-speed plasma cutting.

The plasma cloud is in fact transparent with respect to solid-state lasers, so plasma-assisted melting cutting is only possible with CO2 lasers.

gasification cutting

Vaporized cutting vaporizes the material, minimizing the impact of thermal effects on the surrounding material. This can be achieved by using continuous CO2 laser processing to vaporize low-heat, high-absorption materials such as thin plastic films and non-melting materials such as wood, paper and foam.

Ultrashort pulsed lasers allow this technology to be applied to other materials. The free electrons in the metal absorb the laser and heat up dramatically. The laser pulse does not react with the molten particles and plasma, the material sublimates directly and there is no time for the energy to be transferred to the surrounding material in the form of heat. Picosecond pulses ablate the material with no visible thermal effect, no melting and no burr formation.

Figure 3 Vaporized cutting: the laser vaporizes and burns the material. The pressure of the vapor causes the slag to be expelled from the kerf

Parameters: Adjustment of the machining process

Many parameters affect the laser cutting process, some of which depend on the technical performance of the laser and the machine tool, while others are variable.

polarization (of waves)

Polarization indicates what percentage of the laser light is converted. Typical polarization is usually around 90%. This is sufficient for high quality cutting.

Focus Diameter

The focal diameter affects the width of the incision and can be changed by changing the focal length of the focusing lens. A smaller focal diameter means a narrower incision.

Focus position

The focal point position determines the beam diameter and power density on the surface of the workpiece as well as the shape of the kerf.

Fig. 4 Focal positions: inside the workpiece, on the workpiece surface and above the workpiece

laser power

The laser power should be matched to the type of processing, material type and thickness. The power must be high enough that the power density on the workpiece exceeds the processing threshold.

Figure 5 Higher laser power cuts thicker materials

operating mode

The continuous mode is mainly used for cutting standard contours in metals and plastics in millimeter to centimeter sizes. Instead, to melt perforations or to produce precise contours, pulsed lasers at low frequencies are used.

Cutting speed

Laser power and cutting speed must be matched to each other. Cutting speeds that are too fast or too slow can lead to increased roughness and burr formation.

Fig. 6 Cutting speed decreases with increasing plate thickness

Nozzle Diameter

The diameter of the nozzle determines the gas flow and the shape of the gas stream coming out of the nozzle. The thicker the material, the larger the diameter of the gas jet has to be, and accordingly, the diameter of the nozzle opening has to be increased.

Gas purity and pressure

Oxygen and nitrogen are often used as cutting gases. The purity and pressure of the gas affect the cutting effect.

Technical Parameters

In the early days of laser cutting, the user had to decide on the setting of the processing parameters by means of trial runs. Nowadays, the proven processing parameters are stored in the control unit of the cutting system. For each material type and thickness, there are corresponding data. The table of technical parameters makes it possible to operate the laser cutting machine without problems even for those who are not familiar with this technology.

Laser cutting quality evaluation factors

There are many criteria for determining the quality of laser cut edges. Criteria such as burr form, depression, grain, etc. can be determined with the naked eye; perpendicularity, roughness and kerf width need to be measured with specialized instruments. Material deposition, corrosion, heat affected areas and deformation are also important factors in measuring the quality of laser cutting.

Figure 7 Good cuts, bad cuts. Criteria for evaluating the quality of cut edges

panoramic view

The continued success of laser cutting is hard to match with most other processes. This trend continues today. In the future, the application of laser cutting will also become more and more promising.

-End-

☞Source: World Advanced Manufacturing Technology Forum ☞Editor-in-Chief: Shao Yujie ☞Reviewer: Wu Xiaolan ☞Media Cooperation: 010-88379790-801 ☞Metal Processing Magazine's only submission site: http://tougao.mw1950.cn/

Disclaimer: If the video, picture, text used in this article involves the copyright of the work, please inform us at the first time, and we will confirm the copyright and pay the remuneration according to the national standard or delete the content immediately according to the supporting materials provided by you!