Ball Spin Forming for Flexible and Partial Diameter Reduction in Tubes
Round 1
Reviewer 1 Report
- The content expressed in this article is a well-known spinning forming principle, and no novel technical concepts are felt.
- Some descriptions in the text do not match the diagram or the description is incomplete. For example, in lines 124~125 it expressed "The tube was slightly elongated by forming, and the elongation decreased with the increase in the feed pitch f." But in the two cases of Figure 7, n=140 for Chucked to free and n=85 for Free to chucked, the elongations of f=3.0 are greater than the elongations of f=2.0. These do not match the description. In addition, in the case of D=17mm in Table 4, the thickness increasing ratio is 1.1 (positive value). The result of this positive value seems to violate the principle that the material deformation process must satisfy the volume constant.
- Most of the contents stated in the conclusion are not new discoveries. For example, the contents described in items 1, 3, 4, and 6 are obvious, according to the spinning forming technology and the material deformation process to satisfy the law of volume invariance. The rest of the conclusions do not seem to be representative, because the results shown in Figure 15~Figure 16 and Table 3~Table 4 are the results of 3 different ball diameters, and it seems that only one tube test is made for each ball diameter. In addition, the results shown in Figures 17 and Tables 5 are the results of 4 different fRs, and it seems that only one tube test was performed for each fR. Such results are not representative.
Based on the above description, it is not recommended to publish this article.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
(1) In the set-up of ball die shown in figure 1 and 2, it is questionable if the balls can rotate during the forming process because the outer ring (ball guide) does not rotate. If the ball does not rote during forming, it should be mentioned in the texts for better understanding of the process.
Furthermore, if the ball does not rotate, the frictional condition between ball and tube may be sever. Please add the information of lubricant used in the experiment.
(2) The term of "Pushing pitch" are used in many times, e.g., in the line 199,202, 236-240 and Table 2, etc. However, in Fig.17, the term of "Pushing speed" is used for the same meaning . Please unify these terms used. The "Radial feed rate" is recommended as the unified term.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
An interesting work that presents a method for incremental tube diameter reduction. The methods and the results are adequately presented. The paper can be considered for a potential publication; however, the comments below have to be addressed before publication:
- The introduction has to be re-written in order to better show the state of the art and innovation content. For example, the technique of ball spinning was developed according to your reference list on 1992.
- More detailed and targeted literature review has to be performed in order to support your claims. Very limited references are presented from very specific groups and regions. There are groups around the world that deal with similar projects (e.g. incremental tube forming).
- In lines 36-39 you say that roller spinning is an option but it has very complicated kinematics which is solved with ball spinning. I cannot understand why you say that. It can have exactly the same kinematics with your method. You can even substitute the balls with rollers in your system and better tribological conditions might be achieved (sliding friction vs rolling friction).
- Please name some applications. According to your work the limit of diameter reduction is 10-15 % for this specific tube diameter. Is this reduction adequate for this process for the product to fit in any application?
- In section 2.2.3. the dimensional accuracy was measured only at the beginning, middle and end of the formed region as shown in Figure 6? Are these measurements enough to assess the dimensional accuracy?
- In section 3.1 what is the additional pat that makes it cam-implemented?
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The author responded that the device proposed in this article is different from the traditional device and is novel. However, how to use the servo motor to control the ball guide so that different pushing pitches (0.042, 0.083, 0.125, 0.167) can accurately get the pushing depth (0.5, 1.0, 1.5… etc.). Some explanations should be added in this regard.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
I would like to thank the authors for their response. However, some of my comments have not been addressed adequately. I re-attach those comments below:
- The introduction has to be re-written in order to better show the state of the art and innovation content. For example, the technique of ball spinning was developed according to your reference list on 1992. Note: Rephrasing by adding the word "new" next to the reference of 1992 as a response does not clarify the innovation content and does not prove the the state of the art.
- More detailed and targeted literature review has to be performed in order to support your claims. Very limited references are presented from very specific groups and regions. There are groups around the world that deal with similar projects (e.g. incremental tube forming). Note: Only 1 reference was added and with a sentence similar to the already existing one. More extensive literature review is necessary.
- In lines 36-39 you say that roller spinning is an option but it has very complicated kinematics which is solved with ball spinning. I cannot understand why you say that. It can have exactly the same kinematics with your method. You can even substitute the balls with rollers in your system and better tribological conditions might be achieved (sliding friction vs rolling friction). Note: There is a logic jump here. The disadvantages of spinning over the other methods are clear. How are these disadvantages solved by your method. You just mention that it does not and through the text you describe exactly the same kinematics as in roller spinning.
The above comments have to be clarified in detail within the document.
The rest of my comments have been answered satisfactory, however, please add a sentence in your document for each of them.
Author Response
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Author Response File: Author Response.pdf
Round 3
Reviewer 3 Report
I would like to thank the authors for their response.
To my humble opinion, the paper can be published as is.
