A Numerical Analysis for Ball End Milling Due to Coupling Effects of a Flexible Rotor-Bearing System Using GPEM

Round 1

Reviewer 1 Report

Dear Author(s), the manuscript ‘A Numerical Analysis for Ball End Milling due to Coupling Effects of a Flexible Rotor-Bearing System using GPEM’, Manuscript ID: applsci-2421055, have many strong weaknesses that must be improved suitably.

Please find some crucial suggestions below:

1.      The “Abstract’ section is not completely clear. Firstly, the main proposal/conclusion is not received. The reader is not suggested what can receive in the whole paper discussion. Secondly, the Author(s) should included not the experiment descrition step by step by including only those crucial information. Finally, the shortcut and abbreviations must be removed and firstly presented in the body text of the manuscript.

2.      The ‘Introduction’ section is wide, the review is broaden, however, firstly, the number of cited items is short and, secondly, there is no critical review. When Author(s) are trying to widely present the review in the current state of knowledge, the disadvantages of any mentioned method/procedure and studies/analysis presented in the references must be included. Currently, it looks like the proposed studies are not motivated from the lack in the previous stage of research.

3.      The main motivation in the work, introduced in lines 149-155, does not derive from the critical review, generally the review in the ‘Introduction’ section. In the current form, Author(s) firstly present some previous proposals then, suddenly, give some further studies inquiry. Please try to emphasize your proposed novelty according to the already published studies.

4.      In the section 2, it is not obvious if the Author(s) proposed any new formaulas. This from my understanding that equations (1) and (2) are obtained from the Shiau and Hwang work [9]. Is there any new proposal from the Author(s) in this section? If is, it must be highlighted and, especially, strongyly separated from the previous researches.

5.      In section 3, especially 3.1, as in previous issue, Author(s) did not divided their suggestions from the already used. Not oly equations are not highlighted but some description are not clear to be received from the Author(s) of the manuscript or scholars referenced. Similar for the section 3.2.

6.      According to the two previous comments, the discussion in section 3.3 is not divided by reflectin to the current state of knowledge and newly proposed. What is the main difference from the results obtained from previous studies (already published by other scholars) and those proposed in the manuscript reviewed.

7.      From the whole actions done, the general procedure is not sufficient. Please add the flow chart of the experiment to present your point of view more clearly.

8.      The main problem of the weaknesses of the paper is that nowelty was not highlighted properly. In the discussion section it is still not clear what is proposed. From that matter, the discussion seems to be irrelevant.

9.      The ‘Conclusion’ section must be re-worked. Please emphasize one, general proposal from the others. The sentences in lines 333-339 are not sufficiently convincing the reader.

10.  The ‘References’ should be unified and, especially, formatted according to the journal template requirements, e.g. the abbreviation of the Tribology International journal is ‘Tribol Int’, not ‘Tribology Int’, ref. 28.

Generally, the proposed manuscript must be significantly improved before a resubmission, if allowed by the Editor.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 2 Report

Comments as below:

1.      English grammar should be proofread and corrected. For example, “The determination of the critical speed, mode and unbalance response of the rotor-bearing system is investigated by applying a technique known as the generalized polynomial expansion method (GPEM)”.

2.      A few quantitative and quality results should be added in abstract and conclusion.

3.      Should or not underlined concerning specific methods, kindly check.

4.      The authors can provide any picture in section 2 or 3 to illustrate the model.

Grammar should be corrected.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 3 Report

A brief summary:

The aim of the paper was to conduct a numerical analysis for ball end milling using the generalized polynomial expansion method for a flexible rotor-bearing system. The work is applicable in mechanical engineering as it expands the knowledge on vibration characteristics and displacement of a ball end mill. Based on the analysis it may be possible to better predict machining frequencies and optimize milling parameters for a machine equipped with a flexible rotor-bearing system.

Broad comments:

A significant achievement and main novelty of the presented work is conducting a numerical analysis for ball end milling on a machine tool with a flexible rotor-bearing system using GPEM. The practicality of the subject raises doubts. Are flexible rotor-bearing spindles of milling machine tools currently in industrial use? The authors conducted a numerical analysis with no experimental tests to confirm the validity of the results as well. The paper structure is fine, the literature references are numerous, relevant and mostly up to date. The methods and results are presented in a rather clear way. The editing of the paper is mostly fine, although there some minor errors that should be corrected.

Specific comments:

·        The most important issue is the choice of the subject of the study. Are flexible rotor-bearing spindles of milling machine tools currently in industrial use? If so, authors need to expand the paragraph in the introduction. In addition, authors state that their use may allow for faster spindle speeds and lower cutting forces. However, in the numerical tests, the rpms were not really that high. The highest did not exceed 20k rpm, and the rest was under 10k rpm.

·        The paper would greatly benefit from experimental validation of the results.

·        Line 40 – “… in surface machining…” did authors mean freeform surface machining?

·        Line 132 – what is “radial immersion”?

·        Table 1 – cutting conditions are poorly described. What was the tool material? What was the value of the radial depth? Tool length was 30 mm – was that the whole tool length or the overhang? What was the working length? No info on tool holder as well, which greatly affects cutting conditions. 

·        Table 2 – Why such values of a and b were assumed?

·        The title of the paper could specify that the flexible rotor-bearing system refers to milling machine tool spindle.

·        There are a few typos and editing issues that should be addressed. i.e.: line 55 “theTMM”, line 67 “combiningTMM”, line 188 (3) etc.

The reader can rather easily understand the language of the paper, but there are numerous language errors that should be addressed, i.e. line 34 “…high quality of machined surface become the most concerns in the milling process” etc.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 4 Report

The authors presented an article “A Numerical Analysis for Ball End Milling due to Coupling Effects of a Flexible Rotor-Bearing System using GPEM”. In this paper, the tool-tip responses of ball end milling due to coupling effects of a flexible rotor-bearing system is investigated numerically. The determination of the critical speed, mode and unbalance response of the rotor-bearing system is examined using a technique known as the generalized polynomial expansion method (GPEM).The article can be interesting from an engineering point of view, however there are a few points in the article that require further explanation.

Comment 1:

Abstract

Demonstrate in the abstract novelty, practical significance. Add quantitative and qualitative work results to the abstract. Briefly describe the methods used in the research.

Comment 2:

1. Introduction

Enter subsections

Line 55: Transfer Matrix Method (It should be subchapter 1.1)

Line 61: Finite Element Method (It should be subchapter 1.2)

Line 69: Generalized Polynomial Expansion Method (It should be subchapter 1.3)

Comment 3:

4. Conclusions

Add quantitative and qualitative work results. In addition, it is necessary to more clearly show the novelty of the article and the advantages of the proposed method. What is the difference from previous work in this area? Show practical relevance. Presented conclusions are only a description of the test results. Conclusions should reflect the purpose of the article.

Comment 4:

It is incomprehensible why the authors did not include any figures and tables in the text of the article, but only at the end of the article as attachments. These are serious errors in the layout of the text that significantly hinder the substantive assessment of the article.

Comment 5:

The literature is very well chosen. All equations are derived correctly and very clearly. After minor changes the reviewed article can be considered for publication in the Applied Sciences journal.

Moderate editing of English language required.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

Dear Author(s), the manuscript titled ‘A Numerical Analysis for Ball End Milling due to Coupling Effects of a Flexible Rotor-Bearing System using GPEM’, Manuscript ID: applsci-2421055, has been improved according to the raised requirements so, if allowed by the Editor, can be further processed by the Applied Sciences journal.

Reviewer 3 Report

The authors addressed all the issues. No further comments or questions.