Pulse laser cleaning machine vs CW laser cleaning machine（part 2)

The day before yesterday, we released "Pulse laser cleaning machine vs CW laser cleaning machine（part 1)", the cleaning applications of pulse and CW fiber laser have been tested and compared. Today brings you the results, analysis and conclusions of the preferred parameters of pulse and CW fiber laser.

1. Comparison of macro cleaning conditions

The results of the preferred parameters for pulse laser cleaning of the surface paint layer of the aluminum alloy are shown in Figure 5a, and the results of the preferred parameters for CW laser cleaning of the surface paint layer of the aluminum alloy are shown in Figure 5b. After cleaning with pulse laser, the paint layer on the surface of the sample is completely removed, and the surface of the sample appears metallic white with almost no damage to the substrate. After using CW laser cleaning, the paint layer on the surface of the sample is completely removed, but the surface of the sample appears gray-black, and the substrate of the sample also shows micromelting. Therefore, using CW laser vs pulse laser is more likely to cause damage to the substrate.

The results of the preferred parameters for pulse laser cleaning of the carbon steel surface paint layer are shown in Figure 5c, and the results of the preferred parameters for CW laser cleaning of the carbon steel surface paint layer are shown in Figure 5d. After cleaning with pulse laser, the paint layer on the surface of the sample is completely removed, and the surface of the sample appears gray-black with less damage to the substrate. After cleaning with CW laser, the paint layer on the surface of the sample is also completely removed, but the surface of the sample appears dark black, and a large remelting phenomenon can be seen on the surface of the sample. Therefore, using CW laser vs pulse laser is more likely to cause damage to the substrate.

Figure 5: Comparison of pulse laser and CW laser removal macroscopic effects

2. Microscopic morphology comparison of microscopes

It can be seen from Figure 6(a) that after cleaning the aluminum alloy surface paint layer with pulse laser, the paint on the surface of the sample has been completely removed, and the surface damage of the sample is small and there is no laser grain. Using CW laser to clean the sample table, the paint as shown in Figure 6(b) was also completely removed, but the surface of the sample appeared a serious remelting phenomenon, and laser lines also appeared.

It can be seen from Figure 6(c) that after cleaning the carbon steel surface paint layer with pulse laser, the paint on the surface of the sample has been completely removed, and the surface damage of the sample is small, and the surface surface is relatively flat after cleaning. The paint used to clean the surface of the sample with CW laser as shown in Figure 6(d) was also completely removed, but the surface of the sample appeared a serious remelting phenomenon, and the surface of the sample was uneven.

Figure 6.Comparison of microscopic topography of samples after pulse laser and CW lasert after paint removal

3. Comparison of material surface roughness

The figure below shows a comparison of the surface roughness after laser painting. It can be seen from the figure below that after laser cleaning of the aluminum alloy surface paint layer, the pulse laser has 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 using CW laser cleaning, the damage to the surface of the sample is greater, so the surface roughness of the cleaned sample is 1.5 times the roughness value of the original material and 1.7 times the surface roughness after pulse laser cleaning.

After laser cleaning of the carbon steel surface paint layer, the pulse laser has less damage to the surface of the sample, so the surface roughness of the sample after cleaning is close to or even lower than the raw material. However, after using CW laser cleaning, the damage to the surface of the sample is greater, so the surface roughness of the cleaned sample is 1.5 times the roughness value of the original material and 1.7 times the surface roughness after pulse laser cleaning.

Figure 7.Comparison of surface roughness after laser paint removal

4. Comparison of cleaning efficiency

In terms of aluminum alloy surface painting, the paint removal efficiency using pulse laser is much higher than that of CW laser, which is 7.7 times that of CW laser. The cleaning efficiency using pulse laser is 2.77m²/h, while the cleaning efficiency of CW laser is 0.36m²/h.

In terms of carbon steel surface coating, the paint removal efficiency using pulse laser is also higher than that of CW laser, which is 3.5 times that of CW laser. The cleaning efficiency using pulse laser is 1.06m²/h, while the cleaning efficiency of CW laser is 0.3m²/h.

Figure 8.Pulsed light versus continuous light removal efficiency

Conclusion:

Tests have shown that both CW laser and pulse laser can remove the paint on the surface of the material to achieve the effect of cleaning.

Under the same power conditions, the efficiency of pulse laser cleaning is much higher than that of CW laser, and at the same time, pulse laser can better control the heat input to prevent excessive substrate temperature or micro-melting.

The price of CW lasers has advantages, and the gap in efficiency with pulse laser can be made up by using high-power lasers, but the heat input of high-power CW laser is larger, and the degree of damage to the substrate will also increase. Therefore, there are fundamental differences between the two in application scenarios.

High precision, need to strictly control the substrate heating, requiring substrate lossless applications, such as molds, should choose pulse laser.

For some large steel structures, pipelines, etc., due to the large volume and fast heat dissipation, the requirements for substrate damage are not high, you can choose a CW laser.