Application of the hottest super pulse technology

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Application of super pulse technology in continuous nd:yag laser cutting

1 Overview

in recent years, the laser business division of GSI group has carried out a number of original studies in the R & D and application of pumped nd: YAG light sources to give full play to their maximum performance. The research and development work mainly focuses on the high-power (400 ~ 2000W) and continuous wavelength (CW) laser system, which will directly respond to the maximum deformation and elongation after fracture of the experiment. In addition to the continuous wavelength mode, the system can also work in pulse or adjustable output power mode. Compared with the traditional continuous mode, the peak power can be increased by two times. GSI group first proposed this technology in the early 1990s and successfully applied it in the field of welding and cutting

nd: the output power of YAG laser (CW) is stable and can be adjusted within the range of 10% ~ 100% of the average power. GSI group's unique super modulationtm (ultra pulse) technology can store part of the energy in the laser solution: power supply when there is no laser output or low average power, and then transfer the energy to the working medium when the laser output or high average power, resulting in twice the peak power output as shown in table 1. Therefore, the SM laser can work in the continuous wavelength mode like other lasers, and can generate square wave, sine wave or other repetitive output when the peak power is higher than the rated power. At this time, the full output of the average power can still be achieved. For example, when the temporary load rate of rectangular wave output is 50%, the output power value can reach the continuous wavelength mode during the pulse "on" time of the laser. This is mainly due to the consideration of changing the experimental machine to do the fatigue test for a long time by 200%. Therefore, the average output power is equal to the full rated power of the laser. A typical laser output is shown in Figure 1. In some cases, 200% laser adjustment is not required, which depends on the size of the laser focusing spot, the included angle with the surface, the thickness of the cut material, the type of alloy, the electroplating and galvanized coating on the material surface and other factors. When cutting galvanized steel sheet, aluminum alloy and other materials needed by the automotive industry, the ultra pulse laser has some special advantages due to the instantaneous increase of peak power

Fig. 1 square wave and sine wave waveform under super pulse mode

we will select some advantages to explain the following content. These technical improvements are generally divided into the following three categories:

(1) higher cutting speed

(2) cut at an acute angle with the material surface

(3) less slag hanging and better cutting edge quality

the ultra pulse laser is used to cut galvanized steel sheet and aluminum alloy with different thickness. The results show that the ultra pulse technology can not only ensure the cutting speed and cutting quality, but also reduce the uncontrollable material combustion. In addition, when cutting aluminum alloy and galvanized steel plate, the cutting deviation is reduced by 100% and 400% respectively, and the cutting thickness of aluminum alloy is increased. When cutting complex shaped parts, the average output power is reduced without reducing the cutting quality and peak power

the application fields of ultra pulse laser include: automobile body weld cleaning; Cutting and punching of hydroforming pipes

2. Test conditions

the test object is galvanized steel plate and aluminum alloy. The research object is the cutting speed, edge quality and slag hanging degree under the two cutting modes of continuous wavelength output and super pulse output. See Table 2 for specific cutting parameters

3. Results and discussion

(1) the square wave ultra pulse technology of galvanized steel sheet can improve the cutting efficiency by causing more absorption, and make the ablation front more neat and perpendicular to the material surface. When cutting steel plates less than 2mm, the speed of SM mode is faster than that of continuous output mode, which is especially effective when cutting galvanized steel plates. In the continuous wavelength output mode, the zinc coating will react with the parent material, which is why the thicker the coating and the thinner the steel plate, the worse the notch quality will be. It can be seen from Figure 2 that in the continuous wavelength output mode, the cutting speed decreases abnormally in the middle range of the thickness value. This should be due to the boiling evaporation of the zinc coating, which causes the laser beam to be distributed with the entrepreneur after obtaining the product certification, or reduces the heat absorption of the substrate. The super pulse technology makes the cutting speed faster. Because there is a lag time between the two peak powers, the volatile soot is dispersed before the next peak. Fig. 2 shows the speed comparison of cutting 1.5mm thick galvanized steel plate. See Fig. 3 for the quality comparison of hole back when cutting the same material

Fig. 2 Relationship between cutting speed of galvanized steel plate and material thickness

(2) cutting at an acute angle with the surface when cutting three-dimensional workpiece such as steel pipe, in many cases, the cutting position can only be at an acute angle with the workpiece surface, such as cutting at the end of steel pipe and cutting at the bending of plate. A typical example is the cutting of hydroforming steel pipes for the automotive industry (as shown in Figure 4)

Figure 4 hydroforming steel pipe cutting


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