An Optimization Study on a Novel Mechanical Rubber Tree Tapping Mechanism and Technology

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

Dear Reviewer

Thank you for your letter and for the reviewers “An efficient and experiment of rubber tree tapping strategy：Optimization study” (No.: 2724528). Those comments are all valuable and very helpful for revising and improving our paper. We have revised our manuscript carefully according to the comments and we submitted our revision manuscript in which these points were addressed. All revisions to the manuscript have been highlighted. If you have any question about this paper, please don’t hesitate to contact us.

Comment 1:

Overall comments :

On the form of the manuscript:

-Unclear and wrong use of English. It makes the whole manuscript hard to read and understand. See comments in the manuscript. I deeply recommend the manuscript to be edited by a native English speaker.

- uncomplete, unclear and poorly organised rationale.

Response: Thank you for your suggestions. We have already done a language editing service on Elsevier. We modified major grammatical and structural problems carefully again. We improved the sections of abstract, introduction, materials and methods, results, discussion, conclusions and references. All revisions to the manuscript have been highlighted.

Comment 2:

Title :

Does not reflect well the content, objectives and outcomes of the study.

Unclear wording and vocabulary. Do you mean “an efficient rubber tapping strategy” or “an experiment of an efficient rubber strategy”?

Anyway, the title is too general and not specific enough for the paper's content. A title about the mechanization of rubber tree tapping operation would be more appropriate and attractive.

Response: Thank you for your suggestions. We rewrote the Title as follows:

An optimization study on a novel mechanical rubber tree tapping mechanism and technology

Comment 3:

Abstract

The abstract has the same defects as the rest of the paper: unclear and wrong wording and vocabulary; objectives of the study not clearly and fairly defined. The criteria used to compare the mechanic knife to the manual one (efficiency, operability…) must clearly defined.

Must be reworked after taking into account the suggested modifications on the other sections of the manuscript

Response: Thank you for your suggestions. We rewrote the Abstract after taking into account the suggested modifications as follows.

Abstract: All natural rubber is harvested from rubber tree (Hevea brasiliensis Muell. Arg.) by traditional tapping knives, so rubber tapping still heavily relies on labour. Therefore, this study explored a novel, hand-held mechanical rubber tapping machine for rubber tree harvesting. In this study, a mechanical tapping cutter with vertical blade and adjustable guide was first described. Response surface method was applied to evaluate factors affecting tapping effect. The experimental values were in close agreement with predicted value. Machine tapped latex was comparable in quality to hand tapped latex. Based on the single-factor results, the response surface method (RSM) and the center combined rotation design (CCRD) optimization method were adopted to explore the influence of three influencing factors involved vertical blade height (A), cutting force (B) and spiral angle (C) on tapping effect. Regarding cutting rate of old rubber line (Y₁), cutting time (Y₂), latex flow rate (Y₃), average cutting current (Y₄) as evaluation index of tapping effect, an optimization scheme was determined. The quadratic model well fitted for all the responses. The test results showed that the main factors affecting Y₁, Y₂, Y₃ and Y₄ were A & B, B, A & C and B, respectively. Under optimal conditions, the influencing factors of A, B, and C were 10.24mm, 51.67N, and 24.77°, respectively, when the evaluation index values of Y₁, Y₂, Y₃, and Y₄ were 98%, 8.65ml/5min, 9.00s, and 1.16A. The range of the relative error between the experimental and predicted results was from -11.11% to 11.11%. According to the optimized treatment scheme, a comparison test was designed between mechanical and manual rubber tapping tools. To verify availability and effect of mechanical tapping method preliminarily, the important rubber tapping evaluation indexes included bark thickness, bark excision, latex flow time, cutting time, ash con-tent and cutting depth were selected to serve comparison test. There was no significant difference between hand and mechanical methods except ash content (p<0.05) and cutting time (p<0.01). The mechanical tapping machine proposed in this study is meaningful to improve cutting efficiency, practicality and operability. Furthermore, it provides crucial theoretical references for the development of intelligent tapping machines.

Comment 4: Abstract should contain typical experimental data.

Introduction

The organization of the introduction is pretty good starting from the importance of natural rubber production for key industrial sectors then addressing the issue of manpower availability for the latex harvesting operations, also called tapping. From that, the authors elaborate on the potential benefits of tapping mechanization. Nevertheless, most arguments are not sufficiently developed and documented. They are often based on a single-sentence statement. Essential concepts for the scope of the study such as “efficiency”, “labor intensity” are not sufficiently defined, or not defined at all. This must be done in the introduction to make the rest of the manuscript clearer.

See pdf of the manuscript for specific comments.

Response: Thank you for your suggestions. To define Essential concepts for the scope of the study, we added following sentences in the Introduction section.

A tapping task is usually made of 500 to 700 trees and is completed in 3-4 hours. Tapping workers need get up at 2:00 am at night and begin work in rubber plantation using traditional tapping knives without power.

As rubber tapping evaluation indexes, bark thickness, bark excision, latex flow time, cutting time, ash content and cutting depth were importantly used in rubber production.

In the research of mechnical tapping machine design, mechanical parameter, tapping agronomy and tapping effect are focused currently [13, 19 and 22]. The mechanical parameter manly includes cutting blade, guide, weight, gear and power. The tapping agronomy manly includes cutting force, spiral angle, cutting line, and cutting current. The tapping effect manly includes bark thickness, bark excision, latex flow time, cut-ting time, ash content and cutting rate of old rubber line. The cutting time for a single rubber tree tapping is adopted to evaluate mechanical tapping efficiency generally [13, 19 and 22].

Comment 5:

Comment 5-1:

M&M

The M&M sections must be deeply improved on the form.

First, the organisation of the section must be revised. Better separate the information between 1/ experimental site characteristics (study site)/field experiment design (single factor test, /field measurements/ response surface model test/ comparison test) / field measurements (latex flow, cutting time…) / calculations and statistics. Also see suggestion about moving some parts to supplementary material.

Response: Thank you for your suggestions. We deleted the mechanical analysis and equations of “2.5.1 Blade stress calculation” and added “2.1 Mechanical cutter” and “2.5.2 Blade parameters and force analysis” in Appendix section. The organization of the section was revised as follows.

2.1. Experimental site characteristics

2.2. Field experiment design (single factor test / field measurements / response surface model test / comparison test)

2. 3. Field measurements

2.4. Data analysis and processing

Comment 5-2:

Second, wording and vocabulary must be checked because whole paragraphs are hard to understand and some technical words or parameters are not well defined.

Methods and experimental design must be better explained and justified in relation to the objectives of the study.

Response: Thank you for your suggestions. Wording and vocabulary were checked and improved. To well define some technical words and parameters, we added Table 3 and following sentences in the Field experiment design section.

According to the result of blade parameters and force analysis in Appendix B, the main factors of the blade friction forces were cutting force, vertical blade height, spiral angle and angle of the blade edge. In the common traditional method of hand rubber tapping, the range of spiral angle was 20-30° and angle of the blade edge was 4°. All these reliability data could give reference in mechanical tapping test. In order to determine the range of cutting force and vertical blade height, single-factor experimental design was used (shown in Table1).

Take 20 rows * 40 lines of rubber forest as a test subject, removing the trees of new re-planted, sick, rubber trunk perimeter less than 600mm and no old rubber line, the same 30 sample trees tapped by using mechnical and hand tapping methods alternately were selected to carry out the comparison test (shown in Table 3) and cutting current test. Rubber tree tapped once per three days in the test. Bark thickness, bark excision, latex flow time, cutting time, ash content and cutting depth were selected as rubber tapping evaluation indexes. The evaluation indexes were importantly used in rubber production.

Table 3. A comparison test design of rubber tapping by using two methods alternately.

Mechnical result = (Mechnical 1 + Mechnical 2 + Mechnical 3)/3.

Hand result = (Hand 1 + Hand 2 + Hand 3)/3.

Comment 5-3:

The main limit of experimental design is the number of trees of the comparison test. You compared manual and mechanical tapping on 30 trees. Can you justify that this number of tree is enough 1/to find statistical differences on the effect of the tapping method on latex flow and other parameters related to latex or rubber production, giving the great between trees variability of latex yield 2/ to assess the efficiency of the mechanical tool compared to manual tool. In my view, the efficiency must be assessed on a complete tapping task, i.e. the number of trees one worker tapped on a single tapping day. A tapping task is usually made of 500 to 700 trees and is completed in 3-4 hours. There are a lot of questions on the feasibility of the mechanical tapping at this scale (battery autonomy, physical fatigue or disorders related to the weight of the tool etc..). It’s clearly not the scope of the paper so the objectives and limits of the comparison test must be set accordingly and discussed in the Discusion

Response: Thank you for your suggestions.

We added following sentences in the Introduction section.

The cutting time for a single rubber tree tapping is adopted to evaluate mechanical tapping efficiency generally [13, 19 and 22].

We added following sentences in the Discussion section.

A tapping task is usually made of 500 to 700 trees and is completed in 3-4 hours used traditional tapping knife. According to save 3-5 seconds per tree, a tapping task could save 0.41-0.95 hours used hand-held mechanical tapping machine in theory.

To verify availability and effect of mechanical tapping method preliminarily, a comparison test between hand and mechanical tapping tools is designed and only 30 sample trees with good old rubber line is selected. Six important evaluation indexes in rubber production are selected, including bark thickness, bark excision, latex flow time, cutting time, ash content and cutting depth. The research has great significance to provide theoretical support for the further relevant research.

Comment 5-4: You must justify why factor C “spiral angle” is used in the optimization study. This factor does not depend on the tool settings as the two other factors. How was it handled in the study? You must also explain why the factor C was not studied in the single factor test.

Response: Thank you for your suggestions. To justify why factor C “spiral angle” used, we added following sentences in the Materials and Methods section.

According to the result of blade parameters and force analysis in Appendix B, the main factors of the blade friction forces were cutting force, vertical blade height, spiral angle and angle of the blade edge. In the common traditional method of hand rubber tapping, the range of spiral angle was 20-30° and angle of the blade edge was 4°. All these reliability data could give reference in mechanical tapping test. In order to determine the range of cutting force and vertical blade height, single-factor experimental design was used (shown in Table1).

In the common traditional method of hand rubber tapping, the spiral angle was in the range of 20-30° and angle of the blade edge was 4°. The range of vertical blade height and cutting force could be determined by single factor test. Therefore, three influence factors of vertical blade height, cutting force and spiral angle were adopted in response surface optimization test.

Comment 5-5: The response surface optimization step must be better explained. It is not clear. How do you choose the 20 tests that were ran out of the 729 possible combinations of the tree factors?

Response: Thank you for your suggestions. Response surface methodology (RSM) includes optimization procedures for the settings of factorial variables, such that the response reaches a desired maximum or minimum value. The response is in effect modeled by factorial techniques and ANOVA, but these are extended for more detailed modeling of the effects. RSM is based on the factorial study results (screening, then three-level factorial), and is a type of augmentation where extra treatments are added to focus the effects and improve the predictive power of the model. The additional treatments are located within the factorial space (center point) and out with it (star points) – such a structure is known as a central composite design. On analysis by multiple regression, the enhanced model is produced and the equation can be used to plot the response surface. Contour plots reveal not only optimum levels for factors, but also regions where a response shows the same magnitude. RSM is suitable for the formulation of food products in food development (Bower, 2009). RSM was used by Shirashoji et al. (2006, 2010) as a tool for the investigation of the effect of emulsifying salt concentration and cooking time on the physicochemical and rheological properties of processed cheese. RSM was also applied to optimize a pizza cheese (Motevalizadeh et al., 2018). (reference website :

https://en.wikipedia.org/wiki/Response_surface_methodology

https://en.wikipedia.org/wiki/Central_composite_design).

We added following sentences in the Materials and Methods section.

According to response surface methodology and the structure matrix designed by three times of orthogonal rotation combination design, three influence factors needed 20 standard tests [28-29] (shown in Table 4 in Results section)

Comment 5-6: The relation between the calculation of the blade stress-strain and the objectives of the study is not obvious. You should justify why it is of importance in the introduction and better show the link with the field study. Are there any parameters of the model used for calculation that were measured on the trees? If you are not able to justify it, I suggest to remove this part. It won’t alter the main message of the manuscript and it will make it more consistent and easier to read.

See specific comments in the pdf file of the manuscript.

Response: Thank you for your suggestions. We deleted the mechanical analysis and equations of “2.5.1 Blade stress calculation” and added “2.5.2 Blade parameters and force analysis” in Appendix section.

Comment 6:

Comment 6-1:

RESULTS

Legends of tables and figures are not detailed enough. The table and figure legends must be self-explanatory so as the reader doesn't need to go back to the text to understang the meaning of the codes used in it, what kind of statistical test were run etc...

Response: Thank you for your suggestions. We improved the legends of tables and figures. The codes used in Table (Tab.4, Tab.5, Tab.6, Tab.7 and Tab.8) and Figure (Fig.5 and Fig. 6) was explained.

Comment 6-2: The organization of the sub-section must be revised to avoid repetitions and make them shorter.

Response: Thank you for your suggestions. We deleted repeated content and made them shorter. We wrote partial content in Comparison test as follows.

The average bark thickness, average bark excision, average latex certain velocity, average ash content, average cutting depth, average cutting time, using hand and mechanical tapping methods, were 2.16 mm and 2.19 mm, 7.70 mm and 7.43 mm, 6.40 ml/5min and 7.00 ml/5min, 3.28% and 3.08%, 1.37 mm and 1.40 mm, 16.10 s and 13.33 s, respectively (shown in Fig.11). There was no significant difference between the two tapping methods except ash content (p<0.05) and cutting time (p<0.01) (shown in Table 10).

Compared to V-shape pushing-type tapping tool, bark thickness had an average variation rate of 7.55%, and bark consumption had an average fluctuation rate of 3.62%. Bark thickness was relatively smaller, resulting in a slightly larger cutting depth. The mechanical cutter increased the average latex flow rate by 9.38%, indicating that it was more conducive for rubber discharge. The mechanical cutter significantly reduced the cutting time by 17.20%, indicating that it was faster in a single rubber tree tapping. The ash content increased by 6.10%, but was slightly lower, indicating that mechanical tapping did not contaminate the latex. The cutting depth increased significantly by 21.90%, indicating a greater distance from the cambium and perhaps less possible tree injury.

Comment 6-3: Comparison test. The way the results are presented through figures 15 to 17 suggest the manual and mechanical tools were used on the same 30 trees. That’s not possible and the M&M clearly says that you worked on “30 sample trees by machine”. Therefore, the best way to present the results is by a table giving the 30 tree average value (at least other statistics can be added) and the results of the mean comparison (p-value).

Response: Thank you for your suggestions. We replaced and improved figure 11. We added Table 10. We also added Table 3 and following sentences in the Field experiment design section.

Take 20 rows * 40 lines of rubber forest as a test subject, removing the trees of new re-planted, sick, rubber trunk perimeter less than 600mm and no old rubber line, the same 30 sample trees tapped by using mechnical and hand tapping methods alternately were selected to carry out the comparison test (shown in Table 3) and cutting current test. Rubber tree tapped once per three days in the test. Bark thickness, bark excision, latex flow time, cutting time, ash content and cutting depth were selected as rubber tapping evaluation indexes. The evaluation indexes were importantly used in rubber production.

Table 3. A comparison test design of rubber tapping by using two methods alternately.

Mechnical result = (Mechnical 1 + Mechnical 2 + Mechnical 3)/3.

Hand result = (Hand 1 + Hand 2 + Hand 3)/3.

Figure 11. Comparison tapping effects of 30 rubber trees between hand and mechanical tapping methods: (a) Bark thickness (b) Bark excision (c) Latex flow time (d) Cutting time (e) Ash content (f) Cutting depth.

Table 10. The t-test analysis of tapping effects.

Level of significance *** p<0.001, ** p<0.01, *p<0.05

Mean value 1 and mean standard error 1: Latex tapping using mechanical method.

Mean value 2 and mean standard error 2: Latex tapping using hand tapping method.

Comment 7:

DISCUSSION

The most difficult part to read. The argumentation is confused in both form and content. Most arguments are not supported by references to the appropriate literature making the whole discussion more speculative than a fair analysis of the study results, outcomes and limits.

I suggest to consider organizing the discussion in two main parts: 1/ Is tapping with a mechanic knife feasible? 2/ optimization of the mechanic knife for tapping. And you can add a third part to discuss the large-scale deployment of this tool and the link with autonomous tapping robot.

Response: Thank you for your suggestions. We improved the discussion and removed the redundant parts. We rewrote 4.1 and 4.2 in the discussion section as follows.

4.1. Feasibility of the mechanic cutter

Agricultural machinery is crucial to achieve cost savings, quality improvement, and efficiency enhancement in agriculture. This technology had been used to mechanize a variety of crops, including wheat, corn, rice, and peanuts [47-49]. Large-scale rubber tree planting has been ongoing for more than a century, and conventional methods of cutting rubber panels still relies on manual labour using man-power push or pull knives. Due to the high elasticity of the old rubber line left over after rubber tapping, it should be physically removed before next rubber tapping. Rubber trees are effectively grown in China and are continuously tapped by V-shaped pushing-type tapping tools. Rubber tapping is considered to be a skill-oriented job and relies man manpower completely. The decline in skilled rubber tappers, low income from rubber, and increased labour charges have become increasingly significant issues in rubber production [16-19]. Rubber tapping machines are the urgent need [19].

Is tapping with a mechanic knife feasible? Firstly, it is powered by battery. Rubber tapping worker only need to hold the handle shank and pull the machine along the tapping line easily in rubber tapping. Secondly, rubber tapping worker without technical experience can be trained to master the machine correctly in 3-5 days. The ma-chine is more suit for new rubber tapping workers. Thirdly, the tapping machine set-tings could be adjusted to match specific tree anatomy. By changing the distance be-tween guide and blade, the cutting depth and bark thickness could be adjusted. Compared to V-shape pushing-type tapping tool, the tapping panel after rubber tapping was also clean and smooth and tapping effect was better. Fourthly, the vertical blade with 10mm height could excise old rubber line easily, improve quality and is first applied in the field of rubber tree harvesting. Fifthly, cutting depth in this study significantly increased, reduced tree damage potentially. Tapping panel after rubber tapping is clean and smooth. Compared to V-shape pushing-type tapping tool, the mechanical cutter could be used more easily and efficient by workers after simple training. Ac-cording to the specifications of standards NY/T1088-2006 and NY/T267-2006 in China, the tapping quality of the new tapping machine in this study is comparable to the traditional tapping knife.

In the test, 30 sample trees are selected to verify prototyping test with the optimized treatment scheme. Further validation is needed for large-scale applications in future research. A tapping task is usually made of 500 to 700 trees and is completed in 3-4 hours used traditional tapping knife. According to save 3-5 seconds per tree, a tap-ping task could save 0.41-0.95 hours used hand-held mechanical tapping machine in theory. The characteristics of easy to carry, low cost, simple maintenance make the mechanical tapping machine more feasible. But there are still a lot of questions on the feasibility of the mechanical tapping in field tapping task, including battery autonomy, occupational disease, machine fault, mechanical vibration and noise. Further validation is needed for large-scale applications in future research. The new hand-held tap-ping machine could be used by workers after simple training. This has a good effect on raising farmers' income and reviving the rural economy because it not only reduced time and labour costs but also freed up some labour to work in other enterprises. If it is applied on a large scale, the novel tapping machine could reduce the physical demands, decrease reliance on skilled workers and make tapping machine more practical and operable.

4.2. Optimization of the mechanic cutter

The experimental scheme and research method are credible and feasible. To determine the factors, blade parameters and force analysis is calculated. The main certified factors are cutting force, vertical blade height, spiral angle and angle of the blade edge. According traditional reliability data, the range of spiral angle and the value of blade edge are 20-30° and 4°, respectively. To determine the range of cutting force and vertical blade height for response surface optimization, single-factor test is designed. The range of cutting force and vertical blade height are 8-12mm and 40.00-60.00N, respectively. Based on the calculation and single-factor results, the response surface method (RSM) and the center combined rotation design (CCRD) optimization method are adopted to explore the influence of three influencing factors of vertical blade height (A), cutting force (B) and spiral angle (C). The values of old rubber line (Y1), cut-ting time (Y2), latex flow rate (Y3), average cutting current (Y4) are regarded as evaluation index of tapping effect. The quadratic model well fitted for all the responses. The experimental values are in close agreement with predicted values.

Compared to V-shaped blade, and circular saw blade and blade with only horizontal edge that common applied in mechnical rubber tapping machines [13, 19, 22, 45-46]. The mechanical cutter with vertical blade height has been designed and optimized in the study. It can help excise old rubber line easily and save cutting times. The optimization of cutting force can help reduce mechanical wear and rubber tree dam-age. The optimization of spiral angle can help design tapping line and stabilize latex production. To verify availability and effect of mechanical tapping method preliminarily, a comparison test between hand and mechanical tapping tools is designed and only 30 sample trees with good old rubber line is selected. Six important evaluation indexes in rubber production are selected, including bark thickness, bark excision, latex flow time, cutting time, ash content and cutting depth. The research has great significance to provide theoretical support for the further relevant research.

The bark comprises a water capsule skin, yellow skin, inner layer of sand skin, outer layer of sand skin, and coarse skin from the inside to the outside. The primary section of the bark that produces rubber is the yellow bark. However, damage to the water capsule skin will diminish latex yield. In future studies, we also can attempt using the ultrasound-assisted extraction method to examine the characteristics of latex production [50-55]. With the advancement of information technology, Rubber-tapping intelligent technologies mainly included tapped area detection and new tapping line location [29], object detection algorithm [58], rubber-tapped path detection, night-time rubber tapping line detection [11, 59], rubber-tapping robot forest navigation, and in-formation collection system [13, 22]. One tendency in rubber tapping advancement was the fusion of mechanical cutter and intelligent technology advantages. Addition-ally, it might hasten the global resolution of rubber tapping technology's issues.

Comment 8:

CONCLUSION

The conclusion should not be a summary of the results only. It must recall the main findings of the study, highlight its novelty and opens on perspectives.

Response: Thank you for your suggestions. We added following sentences in the Conduction section.

In general, a novel, hand-held mechanical rubber tapping machine was described. Response surface method was applied to evaluate factors affecting tapping effect. The experimental values were in close agreement with predicted value. Machine tapped latex was comparable in quality to hand tapped latex. We recommends that if the mechanical tapping machine is widely applied in rubber harvesting, it will help reduce the physical demands, decrease reliance on skilled workers and improve tapping efficiency, practicality and operability. Furthermore, it provides crucial theoretical references for the development of intelligent tapping machines.

Best wishes and good luck for you.

Yours sincerely

Lingling Wang

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

I have read with much interest your paper. I think that it is very good and it worth publication in Forests. However, the language needs improvement, as well as parts of the text, including some of the figures which are blurry. Also, please consider to improve the discussion so as to remove the redundant parts which may stand as introduction. Since the readership of the journal would be more interested in the applicability of your tested tool, I would suggest to focus the content more on this and less on the mechanical analysis and equations. Particularly the equations may be difficult to understand by the readership, so I would suggest to add them in Appendix section. In the rest, I think that it significantly advances our knowledge on the rubber harvesting.

BR,

REV.

English is fine, only minor improvements are required in phrasing.

Author Response

Dear Reviewer Thank you for your letter and for the reviewers “An efficient and experiment of rubber tree tapping strategy：Optimization study” (No.: 2724528). Those comments are all valuable and very helpful for revising and improving our paper. We have revised our manuscript carefully according to the comments and we submitted our revision manuscript in which these points were addressed. All revisions to the manuscript have been highlighted. If you have any question about this paper, please don’t hesitate to contact us.

Comment 1: I have read with much interest your paper. I think that it is very good and it worth publication in Forests. However, the language needs improvement, as well as parts of the text, including some of the figures which are blurry.

Response: Thank you for your suggestions. We modified major grammatical and structural problems, including the sections of abstract, introduction, materials and methods, discussion and conclusions. We replaced and improved blurry figures, such as Figure 7, Figure 8, Figure 9, Figure 11, and Figure 12.

Comment 2: Also, please consider to improve the discussion so as to remove the redundant parts which may stand as introduction.

Response: Thank you for your suggestions. We improved the discussion and removed the redundant parts. We rewrote 4.1 and 4.2 in the discussion section as follows.

4.1. Feasibility of the mechanic cutter

Agricultural machinery is crucial to achieve cost savings, quality improvement, and efficiency enhancement in agriculture. This technology had been used to mechanize a variety of crops, including wheat, corn, rice, and peanuts [47-49]. Large-scale rubber tree planting has been ongoing for more than a century, and conventional methods of cutting rubber panels still relies on manual labour using man-power push or pull knives. Due to the high elasticity of the old rubber line left over after rubber tapping, it should be physically removed before next rubber tapping. Rubber trees are effectively grown in China and are continuously tapped by V-shaped pushing-type tapping tools. Rubber tapping is considered to be a skill-oriented job and relies man manpower completely. The decline in skilled rubber tappers, low income from rubber, and increased labour charges have become increasingly significant issues in rubber production [16-19]. Rubber tapping machines are the urgent need [19].

Is tapping with a mechanic knife feasible? Firstly, it is powered by battery. Rubber tapping worker only need to hold the handle shank and pull the machine along the tapping line easily in rubber tapping. Secondly, rubber tapping worker without technical experience can be trained to master the machine correctly in 3-5 days. The ma-chine is more suit for new rubber tapping workers. Thirdly, the tapping machine set-tings could be adjusted to match specific tree anatomy. By changing the distance be-tween guide and blade, the cutting depth and bark thickness could be adjusted. Com-pared to V-shape pushing-type tapping tool, the tapping panel after rubber tapping was also clean and smooth and tapping effect was better. Fourthly, the vertical blade with 10mm height could excise old rubber line easily, improve quality and is first applied in the field of rubber tree harvesting. Fifthly, cutting depth in this study significantly increased, reduced tree damage potentially. Tapping panel after rubber tapping is clean and smooth. Compared to V-shape pushing-type tapping tool, the mechanical cutter could be used more easily and efficient by workers after simple training. Ac-cording to the specifications of standards NY/T1088-2006 and NY/T267-2006 in China, the tapping quality of the new tapping machine in this study is comparable to the traditional tapping knife.

In the test, 30 sample trees are selected to verify prototyping test with the optimized treatment scheme. Further validation is needed for large-scale applications in future research. A tapping task is usually made of 500 to 700 trees and is completed in 3-4 hours used traditional tapping knife. According to save 3-5 seconds per tree, a tapping task could save 0.41-0.95 hours used hand-held mechanical tapping machine in theory. The characteristics of easy to carry, low cost, simple maintenance make the mechanical tapping machine more feasible. But there are still a lot of questions on the feasibility of the mechanical tapping in field tapping task, including battery autonomy, occupational disease, machine fault, mechanical vibration and noise. Further validation is needed for large-scale applications in future research. The new hand-held tapping machine could be used by workers after simple training. This has a good effect on raising farmers' income and reviving the rural economy because it not only reduced time and labour costs but also freed up some labour to work in other enterprises. If it is applied on a large scale, the novel tapping machine could reduce the physical demands, decrease reliance on skilled workers and make tapping machine more practical and operable.

4.2. Optimization of the mechanic cutter

The experimental scheme and research method are credible and feasible. To determine the factors, blade parameters and force analysis is calculated. The main certified factors are cutting force, vertical blade height, spiral angle and angle of the blade edge. According traditional reliability data, the range of spiral angle and the value of blade edge are 20-30° and 4°, respectively. To determine the range of cutting force and vertical blade height for response surface optimization, single-factor test is designed. The range of cutting force and vertical blade height are 8-12mm and 40.00-60.00N, respectively. Based on the calculation and single-factor results, the response surface method (RSM) and the center combined rotation design (CCRD) optimization method are adopted to explore the influence of three influencing factors of vertical blade height (A), cutting force (B) and spiral angle (C). The values of old rubber line (Y₁), cut-ting time (Y₂), latex flow rate (Y₃), average cutting current (Y₄) are regarded as evaluation index of tapping effect. The quadratic model well fitted for all the responses. The experimental values are in close agreement with predicted values.

Compared to V-shaped blade, and circular saw blade and blade with only horizontal edge that common applied in mechnical rubber tapping machines [13, 19, 22, 45-46]. The mechanical cutter with vertical blade height has been designed and optimized in the study. It can help excise old rubber line easily and save cutting times. The optimization of cutting force can help reduce mechanical wear and rubber tree dam-age. The optimization of spiral angle can help design tapping line and stabilize latex production. To verify availability and effect of mechanical tapping method preliminarily, a comparison test between hand and mechanical tapping tools is designed and only 30 sample trees with good old rubber line is selected. Six important evaluation indexes in rubber production are selected, including bark thickness, bark excision, latex flow time, cutting time, ash content and cutting depth. The research has great significance to provide theoretical support for the further relevant research.

The bark comprises a water capsule skin, yellow skin, inner layer of sand skin, outer layer of sand skin, and coarse skin from the inside to the outside. The primary section of the bark that produces rubber is the yellow bark. However, damage to the water capsule skin will diminish latex yield. In future studies, we also can attempt using the ultrasound-assisted extraction method to examine the characteristics of latex production [50-55]. With the advancement of information technology, Rubber-tapping intelligent technologies mainly included tapped area detection and new tapping line location [29], object detection algorithm [58], rubber-tapped path detection, night-time rubber tapping line detection [11, 59], rubber-tapping robot forest navigation, and in-formation collection system [13, 22]. One tendency in rubber tapping advancement was the fusion of mechanical cutter and intelligent technology advantages. Addition-ally, it might hasten the global resolution of rubber tapping technology's issues.

Comment 3: Since the readership of the journal would be more interested in the applicability of your tested tool, I would suggest to focus the content more on this and less on the mechanical analysis and equations. Particularly the equations may be difficult to understand by the readership, so I would suggest to add them in Appendix section.

Response: Thank you for your suggestions. We deleted the mechanical analysis and equations of “2.5.1 Blade stress calculation” and added “2.5.2 Blade parameters and force analysis” in Appendix section.

Comment 4: In the rest, I think that it significantly advances our knowledge on the rubber harvesting.

Response: Thank you for your suggestions.

Best wishes and good luck for you.

Yours sincerely

Lingling Wang

Author Response File: Author Response.pdf

Reviewer 3 Report

Review

In today's highly technical era, natural rubber is one of the most important and one can literally say strategic natural raw materials that, despite all the progress in chemical technologies, cannot be fully replaced by synthetic materials. At the same time, however, the technology for obtaining the starting raw material - raw rubber - is still mainly based on manual labour. The presented article is based on the results of a research study by its authors, dealing with the possibilities of increasing the degree of mechanization in the extraction of raw rubber from the stems of the Hevea brasiliensis plant. The results presented in the paper indicate that there are effective mechanized alternatives to the raw rubber extraction technology of manual cutting of rubber tree bark with hand tools. New means increase the quality of work, while not endangering the very plant from which the rubber is obtained. The article thus brings new interesting knowledge about the given issue, both at the level of scientific research, technical solution and practical application. The information contained in it can be used both in scientific circles and in operational practice. So the topic of the article is current and beneficial.

The abstract of the article is prepared as a dense and sufficiently concise and comprehensible text, which provides sufficient general information about the substantive content of the article. The Abstract is followed by a set of several keywords. Here I would recommend some minor changes to the keywords to better express the main topics of the article. As some words are listed here, they are not clearly directed to the given issue (e.g. "Response surface methodology" or "Central composite rotatable design").

Chapter 1 - Introduction provides a complete broad-based information on the issue of raw rubber extraction from Hevea brasiliensis plants. From this chapter, the reader will get information about the biology of this plant, about the general principles of obtaining rubber from it, as well as information not only about the traditional manual procedures used and hand tools for cutting (grooving) the bark, but also about mechanized or even automated procedures for cutting the bark of the rubber tree in China. At the end of this introductory chapter, the objectives of the research study are clearly defined, which at the same time correspond to the main areas of the presented article.

Chapter 2 – Materials and Methods contains several subsections. Subchapter 2.1 describes the principle of the newly developed mechanical cutter. Although the description is accompanied by a picture, it seems to me to be difficult to understand - it is not described, for example, whether the cutting device is powered by a motor, if so, then it is necessary to state how this drive is implemented and how the device is used when making a cut. It is obvious that the device is held in the hand while working, but other necessary details are unfortunately missing. It should also be stated here how this new device is different (or better) than the existing means for cutting rubber tree bark. I recommend editing this subsection. Other subsections No. 2.2 to 2.6 provide sufficient information about the location of the experimental tests, their arrangement, the methods of measuring the necessary parameters, as well as various calculations, which are sufficiently supported by mathematical equations. In the last subsection 2.6, a flow chart of the research is presented, which provides detailed information on the organization of individual procedural steps of the research study. These subsections are processed in a sufficiently understandable manner and I have no comments on them.

Chapter 3 – Results presents the findings from the research study. In several sub-chapters, one-factor statistical analysis of selected test results (3.1), variation analysis of response surface regression model (3.1), interaction results for response surface (3.3), model verification test (3.4), blade stress-strain analysis (3.5) is presented. In my opinion, subsection 3.6 is particularly significant, which brings the results of the comparison of the current procedure using V-shaped knives with the newly developed prototype hand-held mechanical rubber tapping machine. From a methodological point of view, the entire chapter No. 3 is built very well, the authors use progressive evaluation mathematical-statistical methods and the presented results reflect the goals characterized in chapter 1. The text passages are appropriately supplemented with tables, graphs and photographs from the tests. In this chapter, the authors intensively focus on potential changes in latex production depending on the use of the new tapping method. In my opinion, however, it would also be appropriate here to compare the old and new method of grooving the rubber tree bark from the point of view of work productivity (and perhaps also from the point of view of ergonomic indicators - work effort) - I did not find this information in chapter 3.

Chapter 4 - Discussion assesses the degree of fulfilment of the hypotheses of the research study compared to the achieved results. The texts of individual sub-chapters 4.1 to 4.3 demonstrate, also using comparisons with the results of other authors, that the assumptions established at the beginning of the study were achieved. I have also become convinced that this is the case and therefore have no comments on this chapter. For me, it is a big positive and proof of the success of the research solution that (as the authors state in the article) over 10,000 new mechanical cutters had already been promoted and put to use.

Chapter 5 – Conclusions summarizes the content of the article in a standard way and highlights the essential results of the research study on a new way of grooving the rubber tree. In my opinion, the content of this chapter corresponds to the previous articles and I have no comments on it.

References are written in a standard way, they contain the works of renowned authors, and their scope testifies to the conscientious preparation of the authors during the implementation of the research study and the article itself.

In conclusion, I state that the submitted article presents new original information, is processed on the basis of the authors' scientific approach and their own scientific and research activities, its composition fulfils the requirements for scientific articles.

Author Response

Dear Reviewer Thank you for your letter and for the reviewers “An efficient and experiment of rubber tree tapping strategy：Optimization study” (No.: 2724528). Those comments are all valuable and very helpful for revising and improving our paper. We have revised our manuscript carefully according to the comments and we submitted our revision manuscript in which these points were addressed. All revisions to the manuscript have been highlighted. If you have any question about this paper, please don’t hesitate to contact us.

Comment 1: In today's highly technical era, natural rubber is one of the most important and one can literally say strategic natural raw materials that, despite all the progress in chemical technologies, cannot be fully replaced by synthetic materials. At the same time, however, the technology for obtaining the starting raw material - raw rubber - is still mainly based on manual labour. The presented article is based on the results of a research study by its authors, dealing with the possibilities of increasing the degree of mechanization in the extraction of raw rubber from the stems of the Hevea brasiliensis plant. The results presented in the paper indicate that there are effective mechanized alternatives to the raw rubber extraction technology of manual cutting of rubber tree bark with hand tools. New means increase the quality of work, while not endangering the very plant from which the rubber is obtained. The article thus brings new interesting knowledge about the given issue, both at the level of scientific research, technical solution and practical application. The information contained in it can be used both in scientific circles and in operational practice. So the topic of the article is current and beneficial.

Response: Thank you for your suggestions.

Comment 2: The abstract of the article is prepared as a dense and sufficiently concise and comprehensible text, which provides sufficient general information about the substantive content of the article. The Abstract is followed by a set of several keywords. Here I would recommend some minor changes to the keywords to better express the main topics of the article. As some words are listed here, they are not clearly directed to the given issue (e.g. "Response surface methodology" or "Central composite rotatable design").

Response: Thank you for your suggestions. We deleted words "Response surface methodology" and "Central composite rotatable design". We added words "Optimization design" and "Tapping effect".

Comment 3: Chapter 1 - Introduction provides a complete broad-based information on the issue of raw rubber extraction from Hevea brasiliensis plants. From this chapter, the reader will get information about the biology of this plant, about the general principles of obtaining rubber from it, as well as information not only about the traditional manual procedures used and hand tools for cutting (grooving) the bark, but also about mechanized or even automated procedures for cutting the bark of the rubber tree in China. At the end of this introductory chapter, the objectives of the research study are clearly defined, which at the same time correspond to the main areas of the presented article.

Response: Thank you for your suggestions.

Comment 4: Chapter 2 – Materials and Methods contains several subsections. Subchapter 2.1 describes the principle of the newly developed mechanical cutter. Although the description is accompanied by a picture, it seems to me to be difficult to understand - it is not described, for example, whether the cutting device is powered by a motor, if so, then it is necessary to state how this drive is implemented and how the device is used when making a cut. It is obvious that the device is held in the hand while working, but other necessary details are unfortunately missing. It should also be stated here how this new device is different (or better) than the existing means for cutting rubber tree bark. I recommend editing this subsection. Other subsections No. 2.2 to 2.6 provide sufficient information about the location of the experimental tests, their arrangement, the methods of measuring the necessary parameters, as well as various calculations, which are sufficiently supported by mathematical equations. In the last subsection 2.6, a flow chart of the research is presented, which provides detailed information on the organization of individual procedural steps of the research study. These subsections are processed in a sufficiently understandable manner and I have no comments on them.

Response: Thank you for your suggestions. We added “2.1 Mechanical cutter” and “2.5.2 Blade parameters and force analysis” in Appendix section. We improved the Fig. 14 and added following sentences in the Appendix section.

Operating instruction. The hand-held mechnical rubber tapping machine mainly includes hand shank, mechanical cutter, battery, lumbar bag and power connection cable. Firstly, put on the lumbar bag and keep the battery in lumbar bag. Secondly, Hold the hand shank with one hand, turn on the on-off button and pull the mechanical machine along the tapping line. The tapping worker should move the machine from top to bottom or bottom to top along the tapping line until rubber tapping finished. It also can be used by a traditional tapping method without power.

Figure 14. Examples of rubber tapping equipment and technology.

Comment 5: Chapter 3 – Results presents the findings from the research study. In several sub-chapters, one-factor statistical analysis of selected test results (3.1), variation analysis of response surface regression model (3.1), interaction results for response surface (3.3), model verification test (3.4), blade stress-strain analysis (3.5) is presented. In my opinion, subsection 3.6 is particularly significant, which brings the results of the comparison of the current procedure using V-shaped knives with the newly developed prototype hand-held mechanical rubber tapping machine. From a methodological point of view, the entire chapter No. 3 is built very well, the authors use progressive evaluation mathematical-statistical methods and the presented results reflect the goals characterized in chapter 1. The text passages are appropriately supplemented with tables, graphs and photographs from the tests. In this chapter, the authors intensively focus on potential changes in latex production depending on the use of the new tapping method. In my opinion, however, it would also be appropriate here to compare the old and new method of grooving the rubber tree bark from the point of view of work productivity (and perhaps also from the point of view of ergonomic indicators - work effort) - I did not find this information in chapter 3.

Response: Thank you for your suggestions. To compare the old and new method of grooving the rubber tree bark from the point of view of work productivity, we added some sentences in the sections of Introduction, Results and Discussion. We replaced a figure and added one table in in the Results sections.

We added following sentences in the Introduction section.

The cutting time for a single rubber tree tapping is adopted to evaluate mechanical tapping efficiency generally [13, 19 and 22].

We replaced and improved figure 11 which included contrast index of cutting time in chapter 3. We added Table 10 and following sentences in the Introduction section in chapter 3.

There was no significant difference between the two tapping methods except ash con-tent (p<0.05) and cutting time (p<0.01) (shown in Table 10).

We added following sentences in the Discussion section.

A tapping task is usually made of 500 to 700 trees and is completed in 3-4 hours used traditional tapping knife. According to save 3-5 seconds per tree, a tapping task could save 0.41-0.95 hours used hand-held mechanical tapping machine in theory.

Table 10. The t-test analysis of tapping effects.

Level of significance *** p<0.001, ** p<0.01, *p<0.05

Mean value 1 and mean standard error 1: Latex tapping using mechanical method.

Mean value 2 and mean standard error 2: Latex tapping using hand tapping method.

Figure 11. Comparison tapping effects of 30 rubber trees between hand and mechanical tapping methods: (a) Bark thickness (b) Bark excision (c) Latex flow time (d) Cutting time (e) Ash content (f) Cutting depth.

Comment 6: Chapter 4 - Discussion assesses the degree of fulfilment of the hypotheses of the research study compared to the achieved results. The texts of individual sub-chapters 4.1 to 4.3 demonstrate, also using comparisons with the results of other authors, that the assumptions established at the beginning of the study were achieved. I have also become convinced that this is the case and therefore have no comments on this chapter. For me, it is a big positive and proof of the success of the research solution that (as the authors state in the article) over 10,000 new mechanical cutters had already been promoted and put to use.

Response: Thank you for your suggestions.

Comment 7: Chapter 5 – Conclusions summarizes the content of the article in a standard way and highlights the essential results of the research study on a new way of grooving the rubber tree. In my opinion, the content of this chapter corresponds to the previous articles and I have no comments on it.

Response: Thank you for your suggestions.

Comment 8: References are written in a standard way, they contain the works of renowned authors, and their scope testifies to the conscientious preparation of the authors during the implementation of the research study and the article itself.

Response: Thank you for your suggestions.

Comment 9: In conclusion, I state that the submitted article presents new original information, is processed on the basis of the authors' scientific approach and their own scientific and research activities, its composition fulfils the requirements for scientific articles.

Response: Thank you for your suggestions.

Best wishes and good luck for you.

Yours sincerely

Lingling Wang

Author Response File: Author Response.pdf