1
Comparison of macro cleaning conditions
Figure 5a shows the results of the optimal parameters for the pulsed light cleaning of the aluminum alloy surface paint layer, and Figure 5b shows the results of the optimal parameters for the continuous light cleaning of the aluminum alloy surface paint layer. After cleaning with pulsed light, the paint layer on the surface of the sample is completely removed, the surface of the sample appears metallic white, and there is almost no damage to the substrate of the sample. After using continuous light cleaning, the paint layer on the surface of the sample was completely removed, but the surface of the sample appeared gray-black, and the substrate of the sample also appeared micro-melting. Therefore, the use of continuous light is more likely to cause damage to the substrate than pulsed light.
The results of the optimal parameters for the pulsed light cleaning of the carbon steel surface paint layer are shown in Figure 5c, and the results of the optimal parameters for the continuous light cleaning of the carbon steel surface paint layer are shown in Figure 5d. After cleaning with pulsed light, the paint layer on the surface of the sample is completely removed, the surface of the sample appears gray-black, and the damage to the substrate of the sample is small. After using continuous light cleaning, the paint layer on the surface of the sample is also completely removed, but the surface of the sample appears dark black, and it can be intuitively seen that there is a large remelting phenomenon on the surface of the sample. Therefore, the use of continuous light is more likely to cause damage to the substrate than pulsed light.
2
Microscopic morphology comparison
It can be seen from Figure 6(a) that after using pulsed light to clean the paint layer on the surface of the aluminum alloy, the paint on the surface of the sample has been completely removed, and the surface of the sample has little damage and no laser lines. Using continuous light to clean the sample sheet, as shown in Figure 6(b), the paint is also completely removed, but the surface of the sample has serious remelting and laser lines.
It can be seen from Fig. 6(c) that after using pulsed light to clean the surface paint layer of carbon steel, the paint on the surface of the sample has been completely removed, and the surface of the sample is relatively smooth after cleaning with little damage. The paint was also completely removed using continuous light cleaning, as shown in Figure 6(d), but the surface of the sample was severely remelted, and the surface of the sample was uneven.
3
Material Surface Roughness Comparison
Figure 7 is a comparison chart of the surface roughness after laser paint removal. It can be seen from Figure 7 that after laser cleaning the aluminum alloy surface paint layer, the pulsed light does less damage to the surface of the sample, so the surface roughness of the sample after cleaning is close to that of the original material. However, after continuous light cleaning, the damage to the surface of the sample is relatively large, so the surface roughness of the cleaned sample is 1.5 times that of the original material and 1.7 times that of the surface after pulsed light cleaning.
After laser cleaning the surface paint layer of carbon steel, the pulsed light does less damage to the surface of the sample, so the surface roughness of the sample after cleaning is close to or even lower than that of the original material. However, after continuous light cleaning, the damage to the surface of the sample is relatively large, so the surface roughness of the cleaned sample is 1.5 times that of the original material and 1.7 times that of the surface after pulsed light cleaning.
4
Cleaning efficiency comparison
In terms of paint removal on aluminum alloy surfaces, the paint removal efficiency of pulsed light is much higher than that of continuous light, which is 7.7 times that of continuous light. The cleaning efficiency using pulsed light was 2.77m²/h, while the cleaning efficiency of continuous light was 0.36m²/h.
In terms of paint removal on carbon steel surfaces, the paint removal efficiency of pulsed light is also higher than that of continuous light, which is 3.5 times that of continuous light. The cleaning efficiency using pulsed light is 1.06m²/h, while the cleaning efficiency of continuous light is 0.3m²/h.
In conclusion
Experiments show that both continuous lasers and pulsed lasers can remove the paint on the surface of the material and achieve the effect of cleaning.
Under the same power conditions, the cleaning efficiency of pulsed laser is much higher than that of continuous laser. At the same time, pulsed laser can better control the heat input to prevent the substrate temperature from being too high or micro-melting.
CW lasers have an advantage in price, and can make up for the gap in efficiency with pulsed lasers by using high-power lasers, but high-power CW lasers have greater heat input and increased damage to the substrate. Therefore, there are fundamental differences between the two in application scenarios. With high precision, it is necessary to strictly control the heating of the substrate, and the application scenarios that require the substrate to be non-destructive, such as molds, should choose a pulsed laser. For some large steel structures, pipes, etc., due to the large volume and fast heat dissipation, the requirements for damage to the substrate are not high, and continuous lasers can be selected.
