Laser cleaning machines are gradually becoming known by people because they are environmentally friendly, energy-saving and efficient in the field of cleaning. Compared with traditional chemical cleaning or sandblasting cleaning methods, they are greener and healthier. Laser cleaning machines are divided into continuous cleaning machines and pulse cleaning machines according to the light source laser. What is the difference between these two cleaning methods in industrial applications? Now we use a set of experimental tests to analyze their respective characteristics and applicable application scenarios, hoping to provide useful references for industrial users when choosing the corresponding laser cleaning technology.
Different cleaning principles
- Pulse laser cleaning machines achieve cleaning effects by using high-energy short-pulse laser beams to evaporate or peel off impurities such as dirt on the surface of the target object.
- Continuous laser cleaning machines, on the other hand, use continuously output laser beams to directly irradiate the surface of the target object with high-energy beams, ablating or melting the dirt to achieve the cleaning effect.
Brief conclusion
- Pulse lasers are known for their precision and control.It can remove the surface dirty without damaging the underlying material. Generally suitable for high-precision tasks that require high precision, high efficiency and minimal damage to the substrate.
- Continuous laser cleaning machines are suitable for cleaning large areas and thinner stains, with fast cleaning speed and good results. However, for thicker stains and inorganic materials such as oxides, the cleaning effect of continuous laser cleaning machines is not as good as that of pulsed laser cleaning machines.
Cost Comparison: Pulse vs. CW Laser Cleaning Machines
The price range for pulse laser cleaning machines typically starts from $5000 and can exceed $20,000 depending on features and specifications. In contrast, CW lasers generally range from $3000 to $10,000 for basic models designed primarily for cutting applications adapted for cleaning.
Below is the detail experimental test data :
Test materials
- Laser
The laser model is PW-200w pulse laser and CW2000 is continuous laser. The detailed parameter comparison of the two lasers is shown in Table 1.
Laser Source | 200w | 2000w |
| Brand | Raycus | Raycus |
| Power | ＞200 | ＞2000 |
| Work Model | Pulse Wave | Continus Wave |
| Wavelength | 1064 | 1080 |
| Peak Power | 200000W | 2000w |
Table 1 : Laser Source Compare
- Simple Material
- NO.1 : Aluminum with size 400mm×400mm×4mm spray paint 20um
- NO.2 : Carbon steel with size 400mm×400mm×10mm spray paint 40um
Experimental results
Two lasers were used to remove paint from the surfaces of two materials. The laser cleaning parameters were optimized to obtain the best pulse width, frequency, scanning speed and other parameters, and the cleaning effect and efficiency under the optimized experimental conditions were compared.
Pulse laser cleaning paint layer experiment
500ns | No. | 1# | 2# | 3# | 4# | 5# |
Frequency | 20 | 30 | 40 | 50 | 60 | |
Speedmm/s | 3200 | 4800 | 6400 | 8000 | 9600 | |
200ns | No. | 6# | 7# | 8# | 9# | 10# |
Frequency | 20 | 30 | 40 | 50 | 60 | |
Speedmm/s | 3200 | 4800 | 6400 | 8000 | 9600 | |
100ns | No. | 11# | 12# | 13# | 14# | 15# |
Frequency | 20 | 30 | 40 | 50 | 60 | |
Speedmm/s | 3200 | 4800 | 6400 | 8000 | 9600 |
Table2: Experimental parameters of pulsed laser cleaning of paint layer on aluminum alloy and carbon steel surface
Figure 1. Comparison of pulsed laser cleaning of aluminum alloy surface paint layer under different laser parameters
Figure 2. Comparison of paint layer on carbon steel surface cleaned by pulsed laser under different laser parameters
The experimental results show that short pulse width can easily remove the paint layer on the surface of aluminum alloy and carbon steel compared with long pulse width at the same frequency. At the same pulse width, the lower the frequency, the easier it is to damage the substrate. When the frequency is greater than a certain value, the higher the frequency, the worse the paint removal effect. The experimental results show that the optimal parameters for pulse laser cleaning the paint layer on the surface of aluminum alloy are 15# (laser power 200W, pulse width 100ns, frequency 60kHz, scanning speed 9600mm/s), and the optimal parameters for cleaning the paint layer on the surface of carbon steel are 13# (laser power 200W, pulse width 100ns, frequency 40kHz, scanning speed 6400mm/s). Both parameters can remove the paint layer cleanly and have little damage to the substrate of the sample.
2. Continuous laser paint cleaning experiment
In the continuous light paint removal experiment, the laser power used was 50%, the duty cycle was 20% (equivalent to an average power of 200W), and the frequency was 30kHz. The focal length of the field lens used was 220mm, and the laser focus spot diameter was about 0.2mm. The cleaning area of a single block was 13mm×13mm, and the filling spacing was 0.1mm. The laser repeated scanning twice when cleaning the paint layer on the aluminum alloy surface, and repeated scanning 4 times when cleaning the paint layer on the carbon steel surface. Under the condition that the laser power, duty cycle and frequency remain unchanged, the effect of laser scanning speed on the cleaning effect was tested. The cleaning parameters for paint removal on the aluminum alloy surface are shown in Table 3, and the cleaning effect is shown in Figure 3. The cleaning parameters for paint removal on the carbon steel surface are shown in Table 4, and the cleaning effect is shown in Figure 4.
| No. | 16# | 17# | 18# | 19# | 20# |
| Speedmm/s | 1500 | 1600 | 1700 | 1800 | 1900 |
| No. | 21# | 22# | 23# | 24# | 25# |
| Speedmm/s | 2000 | 2100 | 2200 | 2300 | 2400 |
| No. | 26# | 27# | 28# | 29# | 30# |
| Speedmm/s | 2500 | 2600 | 2700 | 2800 | 2900 |
Table3: Parameters of continuous laser cleaning paint layer on aluminum alloy surface
No. | 31# | 32# | 33# | 34# | 35# |
Speedmm/s | 2800 | 2900 | 3000 | 3100 | 3200 |
No. | 36# | 37# | 38# | 39# | 40# |
Speedmm/s | 3300 | 3400 | 3500 | 3600 | 3700 |
No. | 41# | 42# | 43# | 44# | 45# |
Speedmm/s | 3800 | 3900 | 4000 | 4100 | 4200 |
Table 4 :Experimental parameters of continuous laser cleaning of paint layer on carbon steel surface
Figure 3. Comparison of continuous laser cleaning of aluminum alloy surface paint layer at different laser scanning speeds
Figure 4. Comparison of continuous laser cleaning of carbon steel surface paint layer at different laser scanning speeds
The experimental results show that under the same laser power and frequency, the lower the laser scanning speed, the greater the damage to the substrate. When the scanning speed is greater than a certain value, the faster the scanning speed, the worse the paint removal effect. The experimental results show that the optimal parameters for continuous laser cleaning of the paint layer on the surface of aluminum alloy are 21# (laser power 200W, frequency 30kHz, scanning speed 2000mm/s), and the optimal parameters for cleaning the paint layer on the surface of carbon steel are 37# (laser power 200W, frequency 30kHz, scanning speed 3400mm/s). These two parameters not only remove the paint layer on the surface of carbon steel, but also cause relatively less damage to the substrate of the sample.
Results and analysis
1. Comparison of macroscopic cleaning conditions
The results of the optimal parameters for pulse light cleaning of the paint layer on the surface of aluminum alloy are shown in Figure 5a, and the results of the optimal parameters for continuous light cleaning of the paint layer on the surface of aluminum alloy are shown in Figure 5b. After pulse light cleaning, the paint layer on the surface of the sample was completely removed, the surface of the sample was metallic white, and there was almost no damage to the sample substrate. After continuous light cleaning, the paint layer on the surface of the sample was also completely removed, but the surface of the sample was gray-black, and the substrate of the sample also showed a micro-melting phenomenon. Therefore, compared with pulse light, continuous light is more likely to cause damage to the substrate.
( 5a )
( 5b )
The results of the optimal parameters for pulse light cleaning of the paint layer on the surface of carbon steel are shown in Figure 5c, and the results of the optimal parameters for continuous light cleaning of the paint layer on the surface of carbon steel are shown in Figure 5d. After pulse light cleaning, the paint layer on the surface of the sample was completely removed, the surface of the sample was gray-black, and the damage to the sample substrate was small. After continuous light cleaning, the paint layer on the surface of the sample was also completely removed, but the surface of the sample was dark black, and it can be intuitively seen that there was a large remelting phenomenon on the surface of the sample. Therefore, using continuous light is more likely to cause damage to the substrate than using pulsed light.
( 5c )
( 5D )
2. Microscopic morphology comparison
As can be seen from Figure 6 (a), after using pulsed light to clean the paint layer on the aluminum alloy surface, the paint on the sample surface has been completely removed, and the sample surface has little damage and no laser texture. When using continuous light to clean the sample surface, as shown in Figure 6 (b), the paint is also completely removed, but the sample surface has a serious remelting phenomenon, and laser texture also appears.
( 6a )
( 6b )
As can be seen from Figure 6 (c), after using pulsed light to clean the paint layer on the carbon steel surface, the paint on the sample surface has been completely removed, and the surface damage of the sample is small and the surface is relatively flat after cleaning. When using continuous light to clean the sample surface, as shown in Figure 6 (d), the paint is also completely removed, but the surface of the sample has a serious remelting phenomenon, and the surface of the sample is uneven.
( 6c )
( 6d )
3. Comparison of material surface roughness
Figure 7 is a comparison of surface roughness after laser paint removal. As shown in Figure 7, after laser cleaning of the aluminum alloy surface paint layer, the pulsed light caused less damage to the sample surface, so the surface roughness of the sample after cleaning was close to that of the original material. However, after continuous light cleaning, the damage to the sample surface was greater, resulting in the surface roughness of the sample after cleaning being 1.5 times the roughness of the original material and 1.7 times the surface roughness after pulsed light cleaning.
After laser cleaning of the paint layer on the carbon steel surface, the pulsed light caused less damage to the sample surface, so the surface roughness of the sample after cleaning was close to or even lower than the original material. However, after using continuous light cleaning, the surface damage to the sample was greater, so the surface roughness of the sample after cleaning was 1.5 times the roughness of the original material and 1.7 times the surface roughness after pulsed light cleaning.
4. Comparison of cleaning efficiency
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 of pulsed light is 2.77m²/h, while the cleaning efficiency of continuous light is 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 of pulsed light is 1.06m²/h, while the cleaning efficiency of continuous light is 0.3m²/h.
Conclusion
The experiment shows that both continuous laser and pulsed laser can remove paint from the surface of the material to achieve the cleaning effect. 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 from overheating or micro-melting.
The price of continuous laser has an advantage, and the efficiency gap with pulsed laser can be made up by using high-power laser, but the heat input of high-power continuous light is greater, and the degree of damage to the substrate will also increase. Therefore, there is a fundamental difference between the two in application scenarios. For applications with high precision, strict control of substrate temperature rise, and non-destructive substrate, such as molds, pulsed lasers should be selected. For some large steel structures, pipelines, etc., due to their large size and fast heat dissipation, the requirements for substrate damage are not high, so continuous lasers can be selected.