Raycus Gratitude Visit | Laser welding fearless high reflection
Date:2020-12-23Source:Original article

The absorption rate of high-reflection materials for fiber lasers is not high, resulting in poor processing stability. Whether it is cutting or welding, it is a traditional problem in the field of laser processing. Among them, welding usually produces a return phenomenon that is higher or lasts longer than cutting.


Because of its flat-topped spot, even energy distribution, and better weld formation, fiber delivered direct diode lasers have great advantages in welding applications. In industrial production, materials such as aluminum, copper, brass, and stainless steel have more and more applications. However, in the welding process of these materials, traditional semiconductor lasers often face the problem of sharp reduction in laser life and even burnout due to high reflection.


For laser

What is high reaction?


Generally speaking, high reflectivity refers to the low resistivity of the processed material, smoother surface, and low absorption rate of near-infrared laser. Figure 1 shows the absorption coefficient of common metal elements, which causes a large number of lasers to be emitted, and because most lasers are used in scenarios that are perpendicular to the material or a small inclination angle, the return laser reenters the output head, or even partially returns. The light is coupled into the energy-transmitting fiber and is transmitted in the reverse direction of the fiber to the inside of the laser, making the core components inside the laser continue to be hot.


Figure 1 Laser absorption coefficient of common metal elements


New QBH optical fiber output head high reverse test


In response to the problem of high reflection, Raycus Laser designed a new QBH fiber output head, which can effectively convert the uncontrollable return light into light and heat that can be absorbed, and at the same time improve the heat absorption and heat dissipation capabilities of the output head, thereby avoiding it to the greatest extent the effect of returning light on internal components.


In order to verify the performance of the new optical fiber output head, the RFL-A1500D laser equipped with the output head was subjected to a high-reflection test. The overall test idea is to simulate the user's use environment, even beyond the actual working conditions. 


For the new RFL-A1500D laser at the focal position, the welding is carried out at 90° perpendicular to the copper surface (Note: In normal copper welding, vertical welding is generally not carried out. This test is to test the laser resistance under the most stringent test conditions. Inverse capacity), in the test, set the laser power of 450W, 550W, etc., each incremented by 100W, until the full power output is 1500W, and measure the temperature change of the core device at intervals.


 Figure 2 Red copper anti-high reaction test


As shown in Figure 2, laser welding is performed on the surface of red copper. Due to the low laser absorption rate and high thermal conductivity of red copper, the surface of red copper is always in a mirror state, and a steady stream of laser returns to the fiber output head to verify the output of the new fiber Head resistance to high resistance.


The fiber delivered direct diode laser of the new QBH fiber output head has extremely high anti-high performance


The temperature of the core components inside the laser changes under different powers for 200 minutes of continuous light output, as shown in Figure 3. According to the above results, it can be found that although the laser output power continues to increase, the core devices including device 1, device 2, and device 3 are always at normal operating temperature. The normal operating temperature indicates that the core components are not significantly affected by the return light, thus reflecting the powerful performance of the new QBH optical fiber output head to strip the return light.




Figure 3 Curves of the maximum temperature of each part varying with power under different powers


In order to further test the anti-high reaction capability of the fiber delivered direct diode laser and increase the light power test, each core component is tested in more detail, and the result is shown in Figure 4. When the power is higher than 1000W, it can be seen from Figure 4:

● The temperature of device 1 is similar to the previous test results, and the temperature is maintained between 33.9℃~39.3℃;

● For device 2, the temperature mainly fluctuates between 30℃~35℃;

● For device 3, it is mainly in the range of 35℃~40℃;

● The temperature of device 4 is stable in the range of 33.3℃~38.8℃, and there is no further increase trend, which will not affect the normal operation of the machine.

● On the whole, the operating temperature of the core components inside the machine is always kept between 30°C and 40°C.


Figure 4 Temperature curve of each part with time under high power


In order to further test the long-term anti-high anti-reflection stability of this laser and transmission fiber, continue to extend the light-emitting time for testing. The results are shown in Figure 5. It can be seen that the temperature of each part of the laser with a full power of 1.5kW and continuous light output for 1200min tends to be stable, and there is no significant increase or change. After the high-reverse test, the detected laser power is not attenuated. This shows that the semiconductor laser equipped with the new QBH fiber output head has extremely high anti-high performance.



 Figure 5 The temperature change of each component within 1200min when the power is 1.5kW


Next, we also consider that fiber delivered direct diode lasers are mainly used in the new energy industry, with fiber lasers to form a composite beam welding aluminum alloy. In this regard, we tested the high-reflectivity of the laser's positive focus position perpendicular to the aluminum alloy welding, and the results are shown in Figure 6.



 Figure 6 Temperature changes of various parts of the aluminum alloy laser with full power output


The welding sample of square battery top cover sealing





The welding sample of power battery explosion-proof valve




In actual industrial production, due to the obvious melting of the aluminum alloy surface due to the use of fiber lasers, the reflectivity of the laser will be greatly reduced. However, in order to prevent the emergence of some extreme scenarios, we only use a single semiconductor laser to test, so that the laser faces a more severe test, and the result is still stable as always. On the whole, the temperature of part 3, part 4, or part 5 is lower than 35°C, which is almost the same as the temperature change of processing non-highly reflective materials. According to the above results, it can be seen that when a fiber laser equipped with a new QBH output head is processing high-reflection materials, the effect of the return light on the service life of the laser is minimal.



The three pictures show the measured temperature of different devices






Conventional fiber delivered direct diode lasers have a low anti-high and anti-reaction threshold during the processing of high-reflection materials, which shortens the service life of the laser and even causes the core components of the laser to burn out.



The new QBH fiber output head (iHQB) designed by Raycus strips the return light from the source. The actual test shows that under the full power state, the positive focus position emits light on the copper surface for a long time, the fiber delivered direct diode laser can operate normally, the temperature of the core component does not rise, and the laser power does not decrease; the operating temperature and processing of the core component during the aluminum alloy surface test the performance is the same for non-highly reflective materials. When welding high-reflection materials, it has extremely high anti-reflection performance.


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