Performance Investigation of MQL Parameters Using Nano Cutting Fluids in Hard Milling

Round 1

Reviewer 1 Report

The performance of MQL parameters using nano-cutting fluids in hard milling is investigated. My first comment is about the language used in the paper; the language and grammar of the paper should be totally revised.  There are numerous grammatical mistakes in the paper.

Line 13-15: what’s the difference between fluid type and base fluid here?

Line 156-157 you mentioned “The MQL system is NOGA MiniCool MC1700. Pressure regulator and airflow control valve were used for controlling the flow rate and air pressure.” In MQL air and liquid flow rates are two important papers. Throughout the paper, the authors emphasized air pressure and airflow rate, but I did not see any discussion about liquid or oil flow rate. Was this considered in their experiments?

Line 158: “The emulsion and soybean oil were used for the based cutting fluids of MQL system.” What is the emulsion? What are the rheological properties of these lubricants?

Line 179: Why Surface roughness Ra parameter was chosen? Did the authors investigate the other surface roughness parameters such as Rq?

Line 181: How is Fr calculated? Provide the equation

Throughout the paper, I see some general comments without any scientific base and justification; a few examples:

Line 271-273: “For machining, the materials with low hardness, usually smaller than 30 HRC, soybean oil gives a better lubricating performance. However, for difficult-to-cut materials, like hardened steel with high hardness, emulsion oil brings out better results.” What’s the basis of this? Very vague analysis.

Line 276-277: “Moreover, when machining hard materials, the formation of surface roughness is mainly due to surface scratches of the cutting tool, and the influence of other causes is not much”. What do you mean by the formation of surface roughness?

Line 283-284: “Therefore, the better cooling and lubricating effects make soybean oil better.” The sentence is incomplete and vague.

Line 289: “Al2O3 morphology is closely spherical”. What’s the basis of this statement? Did you use SEM to investigate it?

Author Response

Please see attached file for response.

Author Response File: Author Response.pdf

Reviewer 2 Report

The problem statement needs to be rewritten.

The literature review needs extra recent references about sustainable machining.

The mechanism of using MQL-nanofluid should be fully discussed in detail.

The industrial application of such study should also be highlighted.

Author Response

RESPONSE TO THE REVIEWER 2

We are very grateful for the reviews provided by the editors and each of the external reviewers of this manuscript. Please see below, our detailed response to comments.

1. The problem statement needs to be rewritten.

Answer: Thank you very much. The problem statement was revised carefully and rewritten by following your comment. The changes were put in the red color.

2. The literature review needs extra recent references about sustainable machining.

Answer: The recent references about sustainable machining were added and cited by following your comments (Please see Refs. 39-41, 43-48. 52,54,57). The changes were put in the red color.

3. The mechanism of using MQL-nanofluid should be fully discussed in detail.

Answer: The discussion of the cooling and lubricating mechanism of nano cutting fluids under MQL condition were added by following your comments. The changes were put in the red color.

4. The industrial application of such study should also be highlighted.

Answer: The industrial application of this study was added by following your comments. The changes were put in the red color.

Reviewer 3 Report

1. In abstract, "fluid type, base oil, air pressure, and air flow rate" are mentioned as input parameters. However, most important parameters considered in the study is nano particle.
2. in section 2.1, "The emulsion and soybean oil were used for the based cutting fluids of MQL system". Sentence seems to be wrong.
3. Why only these nano particles are selected? Why 1 wt% is selected?
4. What is the basis for selection of particular cutting conditions?
5. What is the basis for selection of particular base oils? The composition, viscosity, thermal conductivity of base oils are not determined or mentioned anywhere. However, authors claimed those properties in the results and discussion.
6. Most of the explanation is based on statistical analysis instead of technical aspects such as nano particle behaviour in base oil.
7. In section 3 (a), two paragraphs are not properly arranged. i.e. surface roughness study and cutting force study etc.,
8. In section 3 (a), paragraph 1, How ignition temperature is influencing the surface roughness? In this work cutting temperatures are not measured. Why authors discussing about heat generation in hard materials and linked to ignition temperature?
9. In section 3 (b), MoS2 gives more lubricating property and Al2O3 gives better thermal conductivity. Force and surface finish mostly depends on lubricating property than thermal conductivity. But, here Al2O3 shown better results than MoS2. Which is not correlating with literature. 
10. conclusions must be very precise.
11. Many of the recent and good papers on Vegetable oil based nano fluids used MQL are not referred.  
12. Authors should concentrate much on technical aspects of base oils, nano particles, MQL mechanism etc., instead of statistical aspects.

Author Response

RESPONSE TO THE REVIEWER 3

We are very grateful for the reviews provided by the editors and each of the external reviewers of this manuscript. Please see below, our detailed response to comments.

1. In abstract, "fluid type, base oil, air pressure, and air flow rate" are mentioned as input parameters. However, most important parameters considered in the study is nano particle.

Answer:

Thank you very much for your valuable comments. The discussion of fluid type, base oil, air pressure, and air flow rate was added by following your suggestions in the revised manuscript in the red color

1. in section 2.1, "The emulsion and soybean oil were used for the based cutting fluids of MQL system". Sentence seems to be wrong.

Answer:

The sentence was rewritten as “The two different cutting fluids including oil-in-water emulsion (called emulsion) and soybean oil were used for MQL system.” in the revised manuscript. Thank you very much.

1. Why only these nano particles are selected? Why 1 wt% is selected?

Answer:

The selection of nano particles was based on the previous studies and they were cited in the revised manuscript. Thank you very much.

1. What is the basis for selection of particular cutting conditions?

Answer:

The selection of particular cutting conditions was based on the previous studies and they were cited in the revised manuscript. Thank you very much.

1. What is the basis for selection of particular base oils? The composition, viscosity, thermal conductivity of base oils are not determined or mentioned anywhere. However, authors claimed those properties in the results and discussion.

Answer:

Thank you very much. The basis for selection of particular base oils was based from the previous studies, which were cited in Ref.38. The composition, viscosity, and thermal conductivity of base oils were mentioned, measured, and cited in the revised manuscript. Please see Refs. 39,41

1. Most of the explanation is based on statistical analysis instead of technical aspects such as nano particle behaviour in base oil.

Answer:

The discussion of technical aspects about the cooling and lubricating mechanism of nanoparticles and their behavior in base oil was added and cited in the revised manuscript by following your comments.

1. In, two paragraphs are not properly. i.e. surface roughness study and cutting force study etc.,

Answer:

Thank you very much. The section 3 (a) was revised carefully and rearranged by following your comments.

1. In section 3 (a), paragraph 1, How ignition temperature is influencing the surface roughness? In this work cutting temperatures are not measured. Why authors discussing about heat generation in hard materials and linked to ignition temperature?

Answer:

Thank you for your valuable comments. The measurement of heat during cutting process is a very important but is a difficult issue. The authors are building an experimental system to measure the temperature directly from the cutting area and will conduct more studies. Therefore, at present, thermal evaluation is only indirectly evaluated, such as through the color of the chip [51]. The authors totally accept the comments of the reviewers and will continue to study and publish in the next works

The ignition temperature affects the cooling and lubricating ability of the oil. When vegetable oil burns, it will form a hard layer of coal, stick to the cutting edge, cling to the machined surface, hinder the cutting process and cause scratches on the machined surface. Therefore, vegetable oils have a low ignition temperature (for example, soybean oil, the burning temperature is about 450°F (232.2°C)), so for hard machining, the application is limited due to the very high cutting heat generated from the contact zone. Accordingly, soybean oil often burns, thereby reducing its effectiveness in lubrication and cooling. That is the reason why the author discussed about heat generation in hard machining and linked to ignition temperature.

The more discussion was added in the revised manuscript

1. In section 3 (b), MoS₂ gives more lubricating property and Al2O3 gives better thermal conductivity. Force and surface finish mostly depends on lubricating property than thermal conductivity. But, here Al2O3 shown better results than MoS2. Which is not correlating with literature. 

Answer:

This part is the shortcoming of the authors. Thank you for your valuable comment. Al₂O₃ nanoparticles possess the outstanding lubricating ability due to their nearly spherical morphology and also have very good thermal conductivity, which was measured in [41], whereas MoS₂ particles only possess good lubricating ability, the main lubricating mechanism is tribo-film formation [48,49], Therefore, Al₂O₃ gives better results.

The manuscript was revised, cited, and modified by following your comments.

1. Conclusions must be very precise.

Answer:

The conclusions were revised and rewritten to be more precise by following your comments

1. Many of the recent and good papers on Vegetable oil based nano fluids used MQL are not referred.  

Answer:

More recent papers on Vegetable oil based nano fluids used in MQL were cited by by following your comments (Please see Refs. 39-41, 43-48. 52,54,57).

1. Authors should concentrate much on technical aspects of base oils, nano particles, MQL mechanism etc., instead of statistical aspects.

Answer:

The technical aspects of base oils, nanoparticles, MQL mechanism, cooling and lubricating mechanism of each type of nanoparticles were added in the revised manuscript. Thank you for your valuable comments

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

There are some minor grammar issues, make sure to double-check the entire manuscript. 

Reviewer 3 Report

Accept