Experimental Research on Drilling and Cutting Urban Hedge Branches Using Multi-Wavelength Lasers

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1)  There is no information on changes in drilling time visible in Figure 3.

2)  It is recommended to provide some basic labeling guidelines for the images in Figure 3, such as: ① indicating the trend of laser power variation in Figure 3(a), or labeling the specific laser power value corresponding to each hole; ② labeling the laser power in Figure 3(b) and its relationship with Figure 3(a).

3)  Figure 5 needs to indicate whether the drilling diameter is consistently greater than the diameter of the focused light spot. It is recommended to list the calculation formula for δD.

Comments for author File: Comments.pdf

Author Response

Comments 1: There is no information on changes in drilling time visible in Figure 3.

Response 1: 

Thank you for pointing this out. We agree with this comment. Figure 3 is only qualitative indication of the phenomenon happened in the laser ablation and changes in drilling time cannot been figured out.

Therefore, the first and second sentences on Paragraph 3, Page 4 (“Figure 3(a) shows that with the increase of interacting laser power, notable decrease in the drilling time, enlargement of the diameters of drilling holes, and more pro-nounced charring effect have been observed.”) has been changed to (“During the interaction between the laser and the plant, the ablation aperture increases with the rise in energy. This process is accompanied by the presence of flames and smoke, as well as the evaporation of water droplets.”)

And a detailed analysis about the changes in drilling time will be presented in the discussion of Figure 4 in Paragraph 2, Page 5.

Comments 2: It is recommended to provide some basic labeling guidelines for the images in Figure 3, such as: ① indicating the trend of laser power variation in Figure 3(a), or labeling the specific laser power value corresponding to each hole; ② labeling the laser power in Figure 3(b) and its relationship with Figure 3(a).

Response 2:

Thank you for pointing this out. We agree with this comment.

As replied on the above comment, Figure 3 is only qualitative indication of the phenomenon happened in laser ablation. These figures are all illustrated as an example. There are no direct relationships between each of them.

According to your suggestions, the wavelength of the laser used and the laser power density corresponding to each perforation have been labeled in Figures 3(a), 3(b) and 3(c) respectively.

Besides, the first sentence on Paragraph 3, Page 4 (“Figure 3(a) shows that with the increase of interacting laser power, notable decrease in the drilling time, enlargement of the diameters of drilling holes, and more pronounced charring effect have been observed.”) has been changed to (“During the interaction between the laser and the plant, the ablation aperture increases with the rise in energy. This process is accompanied by the presence of flames and smoke, as well as the evaporation of water droplets. For example, during the process of ablating the hedge with a 450 nm laser, as the energy density increased from 200 W/cm² to 600 W/cm², the diameter of the ablation hole gradually enlarged, as shown in Figure 3(a).”)

The third sentence on Paragraph 3, Page 4 (The increase in laser power also results in a more vigorous reaction, characterized by occasional flames and the emission of dust particles, as shown in Figure 3(b).”) has been change to (“Figure 3(b) depicts the irradiation of plants with an 808 nm laser at a power density of 1000 W/cm², causing the plants to ignite.”)

 

Comments 3: Figure 5 needs to indicate whether the drilling diameter is consistently greater than the diameter of the focused light spot. It is recommended to list the calculation formula for δD.

Response 3:

Thank you for pointing this out. We agree with this comment.

“δD is the difference between the drilling hole and the laser spot diameter, which is affected by the laser power density and sample material used in the experiment. Its formula is: δD=D(drilling hole diameter)-D(laser focus diameter)”. The diameter of the ablated hole can be smaller than the focus spot. In this case, δD is negative, which can be found in Reference [7].

But in our experiments, the diameters of the penetrating hole obtained are always larger than the spot diameter using laser power density from 2×10² W/cm² to 7×10² W/cm².

We have added the formula and explain in the second sentence on Paragraph 2, Page 6,(“δD is the difference between the drilling hole and the laser spot diameter, which reflects the utilization rate of laser energy absorbed by plants. δD=D(drilling hole diameter)-D(laser focus diameter).”)

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

--.---

Author Response

Thank you very much for your thorough review. Your support is greatly appreciated.

We have revised the manuscript based on the editor's and reviewers' comments, and the updated manuscript is attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This is a very interesting paper about the experimental treatment of green hedge branches using lasers of different wavelengths, analyzing their effects on cutting and processing performance. The results are well presented and conclusions are well supported by the experimental results. The reviewer would like to recommend this paper to be published if the following issues can be clarified.

1.“The layer of carbide formed by cutting the hedge branches 18 can effectively block the invasion of bacteria, which is the advantage of laser cutting in the field of 19 horticulture.”Could you briefly explain what specific effects the prevention of bacterial invasion mentioned here has ?

2.“These processes all used pulse widths of more than a millisecond and long wave- length CO2 lasers.”You mention here that the CO2 lasers have long wavelengths. What is the specific wavelength of these CO2 lasers? Please specify.

3. In Introduction part, the review on laser manufacturing technology is not comprehensive. The following literatures could give authors more insights into this field: 10.1016/j.ijmachtools.2022.103954, 10.1016/j.cja.2021.01.003, 10.1016/j.ijmachtools.2021.103745.

4.“Figure 1. (a) Experimental setup (1) fiber-coupled diode lasers, (2) scanning galvanometer, (3) focusing lens, (4) a CCD camera, (5) a power meter, (6) sample and platform; (b)Focal spot of 1064nm laser beams.”In Figure 1(a), the devices labeled 4 and 5 are not clearly expressed. These are obviously two separate devices, but you have drawn them together. Please revise this.

5.“Figure 3(a) shows that with the increase of interacting laser power, notable decrease in the drilling time, enlargement of the diameters of drilling holes, and more pronounced charring effect have been observed.”The text mentions that with the increase of laser power, there is a notable decrease in drilling time. However, I cannot see any indication of time reduction from the figure you provided. How did you conclude that there is a significant decrease in drilling time based solely on this figure? Please provide additional explanation.

6.“Surface carburization of the hedge branches is stronger irradiated by laser pulses with a power density of about 5×10-2 W/cm² than with a power density of about 6×10-2 W/cm².” Why is carbonization more severe at lower power density? Please explain clearly.

7.“The preliminary results presented show that a fiber-coupled diode laser with the central wavelength of 450 nm may be successfully applied to cut hedge branches.” You need to clearly state the specific advantages of the 450 nm laser, rather than glossing over them. Please express this clearly.

Comments on the Quality of English Language

 The English could be improved to more clearly express the research.

Author Response

Comments 1: “The layer of carbide formed by cutting the hedge branches 18 can effectively block the invasion of bacteria, which is the advantage of laser cutting in the field of 19 horticulture.”Could you briefly explain what specific effects the prevention of bacterial invasion mentioned here has ?

Response 1:

The surface of cuts made with a saw, or shears reveals extensive cell damage and numerous cracks that enable pathogen invasion of the affected plants. When laser cutting hedge branches, the high temperature generated by the laser causes the surface of the branches to form a layer of carbonized material. This carbonized layer provides a certain degree of protective function, which primarily manifests in the following aspects:

The carbonized layer helps to seal the surface of the cutting surface, thereby reducing water loss.

The cellular structures of the cut surfaces were examined, with some of them found to be covered with a layer of compacted, charred cells. The carbonized layer prevents the external environment from directly contacting the healthy part of the branch through a physical barrier, effectively reducing the chance of bacteria invading the plant through the incision and reducing the risk of infection.

Paragraph 3, Page 9 (“This carbonized layer provides a certain degree of protective function, it helps to seal the surface of the cutting surface, thereby reducing water loss. The carbonized layer prevents the external environment from directly contacting the healthy part of the branch through a physical barrier, effectively reducing the chance of bacteria invading the plant through the incision and reducing the risk of infection. This is beneficial to our research.”) has been added.

 

Comments 2: These processes all used pulse widths of more than a millisecond and long wave- length CO2 lasers.”You mention here that the CO2 lasers have long wavelengths. What is the specific wavelength of these CO2 lasers? Please specify.

Response 2:

We agree with the reviewer’s suggestion, and we have made targeted modifications.

We have added the wavelength using “(XXμm/nm)” following the related references in the introduction part. Take reference [9] as an example: “Malachowski [9] explored CO₂ laser (10.6 μm) cutting of green branches for possible laser tree pruning applications (1984)”.

The same change is made in Reference [10],[12],[13],[16],[19],[22],[24].

 

Comments 3: In Introduction part, the review on laser manufacturing technology is not comprehensive. The following literatures could give authors more insights into this field: 10.1016/j.ijmachtools.2022.103954, 10.1016/j.cja.2021.01.003, 10.1016/j.ijmachtools.2021.103745.

Response 3:

Thanks for the reviewer’s suggestion. According to the literatures you provided, we searched the articles on laser manufacturing and had a new understanding of the laser manufacturing field.

So, we newly added 12 references, including the ones the reviewer suggested, in the introduction part. The numbers of them are listed as follows and have been added in the Reference part.

[4] Qian W, Cai J, Xin Z, et al. Femtosecond laser polishing with high pulse frequency for improving performance of specialised aerospace material systems: MCrAlY coatings in thermal barrier coating system[J]. International Journal of Machine Tools and Manufacture, 2022, 182: 103954.

[5] Park, S.-H.; Liu, P.; Yi, K.; Choi, G.; Jhang, K.-Y.; Sohn, H. Mechanical Properties Estimation of Additively Manufactured Metal Components Using Femtosecond Laser Ultrasonics and Laser Polishing. International Journal of Machine Tools and Manufacture 2021, 166, 103745, doi:10.1016/j.ijmachtools.2021.103745.

[6] Pan, X.; He, W.; Cai, Z.; Wang, X.; Liu, P.; Luo, S.; Zhou, L. Investigations on Femtosecond Laser-Induced Surface Modification and Periodic Micropatterning with Anti-Friction Properties on Ti6Al4V Titanium Alloy. Chinese Journal of Aeronautics 2022, 35, 521–537, doi:10.1016/j.cja.2021.01.003.

[7] Nath, S.; Waugh, D.G.; Ormondroyd, G.; Spear, M.; Pitman, A.; Curling, S.; Mason, P. [12] Laser Incising of Wood: A Review.

Hernandez-Castaneda, J.C.; Crouse, P.; Li, L. High-Power Yb-Doped Fibre Laser for Cutting Dry Pine Wood. 2007.

[13] Hernandez-Castaneda, J.C.; Sezer, H.K.; Li, L. Statistical Analysis of Ytterbium-Doped Fibre Laser Cutting of Dry Pine Wood. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 2009, 223, 775–789, doi:10.1243/09544054JEM1397.

[16] Fukuta, S.; Nomura, M.; Ikeda, T.; Yoshizawa, M.; Yamasaki, M.; Sasaki, Y. UV Laser Machining of Wood. Eur. J. Wood Prod. 2016, 74, 261–267, doi:10.1007/s00107-016-1010-9.

[17] Lan, Y.-P. Laser-Optics-Based Method to Suppress Mikania Micrantha Growth. Sci Rep 2022, 12, 19864, doi:10.1038/s41598-022-24451-8.

[18] Kortsalioudakis, N.; Petrakis, P.; Moustaizis, S.; Adamopoulos, S.; Karastergiou, S.; Passialis, C. AN APPLICATION OF A LASER DRILLING TECHNIQUE TO FIR AND SPRUCE WOOD SPECIMENS TO IMPROVE THEIR PERMEABILITY.

[19] Fukuta, S.; Nomura, M.; Ikeda, T.; Yoshizawa, M.; Yamasaki, M.; Sasaki, Y. Wavelength Dependence of Machining Performance in UV-, VIS- and NIR-Laser Cutting of Wood. J Wood Sci 2016, 62, 316–323, doi:10.1007/s10086-016-1553-8.

[20] Azaman, M.I.H.; Mahdi, M.A.; Ahmad, M.R.; Shuib, A.R.; Khalid, M.R.; Bakri, M.A.; Md Radzi, M.K.F.; Ramli, A.S. Optimisation of Parameters Laser Cutting of Oil Palm Fronds Using Fibre Pulsed Laser of 1064 Nm Wavelength System. Adv Agric Food Res J 2020, 1, doi:10.36877/aafrj.a0000108.

[23] Wang, M.; Leal-Naranjo, J.-A.; Ceccarelli, M.; Blackmore, S. A Novel Two-Degree-of-Freedom Gimbal for Dynamic Laser Weeding: Design, Analysis, and Experimentation. IEEE/ASME Trans. Mechatron. 2022, 27, 5016–5026, doi:10.1109/TMECH.2022.3169593.

 

Comments 4: Figure 1. (a) Experimental setup (1) fiber-coupled diode lasers, (2) scanning galvanometer, (3) focusing lens, (4) a CCD camera, (5) a power meter, (6) sample and platform; (b)Focal spot of 1064nm laser beams.”In Figure 1(a), the devices labeled 4 and 5 are not clearly expressed. These are obviously two separate devices, but you have drawn them together. Please revise this

Response 4:

Thank you for pointing this out. We agree with this comment. The (4) and (5) in Figure 1 (a) represent the CCD camera and the laser power meter respectively. We re-annotated Figure 1 and explained it more clearly.  

In the first and second sentences on Paragraph 1, Page 3 (“A beam sampler (7) is added to the laser optical path diagram, so that a sampled beam light can be measured by a CCD (4) and a laser power meter (5). In the experiment, the position of the CCD is conjugated with the position of the laser focal plane, and the size of the focused spot can be accurately measured. In the meantime, the laser power can be calibrated, measured and monitored in real time.”) has been added.

 

Comments 5: Figure 3(a) shows that with the increase of interacting laser power, notable decrease in the drilling time, enlargement of the diameters of drilling holes, and more pronounced charring effect have been observed.”The text mentions that with the increase of laser power, there is a notable decrease in drilling time. However, I cannot see any indication of time reduction from the figure you provided. How did you conclude that there is a significant decrease in drilling time based solely on this figure? Please provide additional explanation.

Response 5:

Thank you for pointing this out. We agree with this comment. Figure 3 is only qualitative indication of the phenomenon happened in the laser ablation and changes in drilling time cannot been figured out.

Therefore, the first and second sentences on Paragraph 3, Page 4 (“Figure 3(a) shows that with the increase of interacting laser power, notable decrease in the drilling time, enlargement of the diameters of drilling holes, and more pro-nounced charring effect have been observed.”) has been changed to (“During the interaction between the laser and the plant, the ablation aperture increases with the rise in energy. This process is accompanied by the presence of flames and smoke, as well as the evaporation of water droplets.”)

And a detailed analysis about the changes in drilling time will be presented in the discussion of Figure 4 in Paragraph 2, Page 5.

 

Comments 6: “Surface carburization of the hedge branches is stronger irradiated by laser pulses with a power density of about 5×10² W/cm² than with a power density of about 6×10² W/cm².” Why is carbonization more severe at lower power density? Please explain clearly.

Response 6:

Thank you for pointing this out. We agree with this comment.

The degree of carbonization is firstly depended on the laser power. That is to say, the greater the power, the greater the degree of carbonization [7]. However, in our results, the degree of carbonization of 500 W/cm² is larger than 600 W/cm². In our opinion, the ablation time is also one of the most important factors for laser carbonization. With the laser power density used in our experiments, the degree of carbonization mainly depends on the time of exposure of the workpiece, rather than the power of the laser beam, which is consistent with experimental results described in reference [10].

Combined with the analysis of Figure 4, when the laser power exceeds 600 W/cm², the drilling time is gradually stable with the increase of laser power. The two power densities of 500 W/cm² and 600 W/cm² used in the experiment are at the critical values. The carbonization degree of the hedge is mainly affected by the laser ablation time, rather than the laser power in this power density range.

We have added the above analysis in the third sentence on Paragraph 2 Page 9, (“In our opinion, the ablation time is also one of the most important factors for laser carbonization. With the laser power density used in our experiments, the degree of carbonization mainly depends on the time of exposure of the workpiece, rather than the power of the laser beam, which is consistent with experimental results described in reference [10].”) and on Paragraph 3 Page 9,(“This carbonized layer provides a certain degree of protective function, it helps to seal the surface of the cutting surface, thereby reducing water loss. The carbonized layer prevents the external environment from directly contacting the healthy part of the branch through a physical barrier, effectively reducing the chance of bacteria invading the plant through the incision and reducing the risk of infection. This is beneficial to our research.”)

 

Comments 7: “The preliminary results presented show that a fiber-coupled diode laser with the central wavelength of 450 nm may be successfully applied to cut hedge branches.” You need to clearly state the specific advantages of the 450 nm laser, rather than glossing over them. Please express this clearly

Response 7:

Thank you for pointing this out. We agree with this comment.

Therefore, we rewrote the conclusion section and carefully summarized the previous results. The changes are as follows:

Paragraph 3, Page 10, (“The difference(δD) between the hole diameter and the laser focal spot diameter reflects the utilization of the laser. The smallest difference between the ablation hole diameter and the spot diameter was observed after irradiation with the 450 nm laser, while the largest difference was observed after irradiation with the 808 nm laser. This indicates that the 450 nm laser has higher energy utilization efficiency during the process.”) has been added.

The last sentence on Paragraph 4, Page 10, (“The maximum allowable incident angle is 18.76°, which is the largest compared with that of using other wavelength lasers.”) has been changed to (“The maximum allowable incident angles for the four wavelengths are 18.756°, 14.922°, 13.217°, and 14.135°, respectively.”).

Paragraph 6, Page 10, (“The cutting surfaces were covered with a layer of charred cells. This could prevent the wound invasion caused by the laser beam. The degree of carbonization is related to the cutting time. The longer the cutting time, the greater the degree of carbonization. When the power density is high, the cutting time is short. The carbonization degree of the cutting surface after using 450 nm laser is less than that of other wavelengths, which not only helps prevent pests and diseases but also avoids excessive carbonization.”) has been added.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

none

Comments on the Quality of English Language

good