Experimental Investigation of Thrust Force in the Drilling of Titanium Alloy Using Different Machining Techniques
Round 1
Reviewer 1 Report
The manuscript entitled “-metals-1980816-Ti Drilling” dealing with driling has been reviewed. The paper has been nicely written but needs significant improvement. Please follow my comments.
1. The abstract needs to be improved by adding some statistical values.
2. Please briefly introduce the process in the introduction.
3. Add more detail about the standard for the measurements.
4. Replace figure 2 with a high-quality figure. Data acquisition and oscilloscope are not clear.
5. The text has some typos. Please check them.
6. Ti has many usage and recently it is used in Additive Manufacturing for different industries. To highlight your contribution read and add the following four papers for the usage of Ti in additive manufacturing.
· Laser powder bed fusion (LPBF) of NiTi alloy using elemental powders: the influence of remelting on printability and microstructure
· Additive manufacturing for prostheses development: state of the art
· Sandwich structure printing of Ti-Ni-Ti by directed energy deposition
· Ti6Al4V scaffolds fabricated by laser powder bed fusion with hybrid volumetric energy density
Author Response
- The abstract needs to be improved by adding some statistical values.
Thank you very much for your advice, some recommended parameters and statistical values have been added in the abstract.
- Please briefly introduce the process in the introduction.
According to your comment, the Introduction has been modified, and the drilling techniques mentioned in this article have been briefly introduced in the second paragraph and the beginning of the third, fourth, and fifth paragraphs.
- Add more detail about the standard for the measurements.
The standard for the measurement was further explained in the first paragraph of 3.1.2.
The mean, maximum and peak-to-valley values were acquired from the time-domain waveform of the stable drill-in stage. To ensure data accuracy, the average value of five acquisitions in different wavebands was taken as the final result.
- Replace figure 2 with a high-quality figure. Data acquisition and oscilloscope are not clear.
Figure 2 has been replaced by a clearer picture.
- The text has some typos. Please check them.
The language and writing of the manuscript have been rechecked and modified.
- Ti has many usage and recently it is used in Additive Manufacturing for different industries. To highlight your contribution read and add the following four papers for the usage of Ti in additive manufacturing.
- Laser powder bed fusion (LPBF) of NiTi alloy using elemental powders: the influence of remelting on printability and microstructure
Additive manufacturing for prostheses development: state of the art
Sandwich structure printing of Ti-Ni-Ti by directed energy deposition
Ti6Al4V scaffolds fabricated by laser powder bed fusion with hybrid volumetric energy density
Thank you very much for your paper recommendation, I cited one of them due to the difference in research theme. However, I have updated the References according to the relevant literature of the recent five years in the Web-of-Science database.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is about the experimental investigation on thrust force in drilling of titanium alloy using different machining techniques. The manuscript is well written. The study has good and important results.
It is required to consider following comments to make the manuscript suitable for publication.
Point 1: There are too many abbreviations. They can be given in a separate table at the end of manuscript.
Point 2: In the introduction section, there are studies that are very old in previous studies. Make sure that the references consist of current studies, especially those of the last 5 years.
Point 3: The precursory checks are important to obtain correct results before drilling tests.
Have authors conducted any precursory checks to determine the axial run out on the spindle?
Point 4: Authors say:
" ..... its characteristic values were collected ...."
In the conclusions section, it is not specified which of the applied drilling parameters is appropriate and recommended.
Optimum parameters and other numerical results of each DD, UVD, PD and UVPD methods must be presented in the "Conclusions" section.
Point 5: when the trust force is appropriate, what about the surface quality (surface roughness, burr formations and shapes)?
As it is known, it is not possible to tell everything about surface quality by looking at the chips after drilling.
In addition, is it possible to add increased magnification images of the chips to examine the chip forms in detail?
Author Response
Point 1: There are too many abbreviations. They can be given in a separate table at the end of manuscript.
Two tables including Abbreviations and Nomenclature have been supplied in the part of Appendix A.
Point 2: In the introduction section, there are studies that are very old in previous studies. Make sure that the references consist of current studies, especially those of the last 5 years.
Thank you for your reminder. I have updated the References according to the relevant literature of the recent five years in the Web-of-Science database.
Point 3: The precursory checks are important to obtain correct results before drilling tests.
Have authors conducted any precursory checks to determine the axial run out on the spindle?
Thank you, this question is very professional.
Before this test, we check only the radial runout of the spindle because of higher axial stiffness of the spindle. The measured result of radial runout is less than 5μm that is within the specified range. Furthermore, the vibration state of the workpiece is monitored throughout the process of drilling.
Point 4: Authors say:
" ..... its characteristic values were collected ...."
This description was modified as “……its mean, maximum and peak-to-valley values were acquired……”
In the conclusions section, it is not specified which of the applied drilling parameters is appropriate and recommended.
Optimum parameters and other numerical results of each DD, UVD, PD and UVPD methods must be presented in the "Conclusions" section.
The conclusion has been further modified according to your advice, the appropriate amplitude of ultrasonic vibration has been provided, and the force reduction effect of UVD and UVPD has also been digitally described.
Point 5: when the trust force is appropriate, what about the surface quality (surface roughness, burr formations and shapes)?
With the same material removal rate (MRR), less thrust force often means better surface quality and smaller burr dimension. However, the shape accuracy of the machined hole may not be improved. but it is directly related to the runout that you mentioned above.
This result has been confirmed by many researchers.
As it is known, it is not possible to tell everything about surface quality by looking at the chips after drilling.
You are right. However, chip deformation can reflect the cutting force to a certain extent, because cutting force is mainly derived from material deformation and interface friction in cutting machining according to the cutting theory.
In addition, is it possible to add increased magnification images of the chips to examine the chip forms in detail?
I think that this approach should be appropriate because the difference in chip deformation between drilling techniques is mainly reflected in detail. And this approach is used by many researchers.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper is interesting and describes important aspects of reduction of the thrust force during the drilling process. However, I suggest that the Authors address the following issues:
- How many drilling trials were made using each technique;
- Was each trial made using a new drill, and was the drill wear process impact on the thrust force analysed;
- No scale at the photographs of chips in Table 3;
- On what basis the vibration acceleration was expressed with Formula 1.
Author Response
- How many drilling trials were made using each technique;
In this study, the amplitude and feedrate were variables and they took five and two levels respectively. The experiment scheme of the single factor was used and each drilling trial was repeated three times. So, the experimental number of DD, PD, UVD, and UVPD were 12, 12, 30, and 30 respectively.
- Was each trial made using a new drill, and was the drill wear process impact on the thrust force analysed;
This question is very professional.
The drilling techniques and amplitude are the focus of this research. To reduce the impact of drill wear on thrust force, we choose the high-performance HSS twist drill made in Spain, and no more than ten holes were machined using per new drill bit.
- No scale at the photographs of chips in Table 3;
Sorry, the photographs of chips in Table 3 were taken by a camera. The experimental chips have been thrown away due to the storage difficulty. However, I think that it should be possible to judge the basic morphology of these chips according to the current photographs.
- On what basis the vibration acceleration was expressed with Formula 1.
Thank you for your reminder. Formula 1 was derived from the displacement equation of standard sine vibration . The manuscript has also been modified.
Round 2
Reviewer 1 Report
The paper is ready to publish.
Reviewer 3 Report
The authors have addressed the remarks concerning the previous version of the paper.
They have satisfactorily answered the questions.
I believe that that paper in its present form is fit for publication.
