Combined Processing of Micro Cutters Using a Beam of Fast Argon Atoms in Plasma

Round 1

Reviewer 1 Report

The authors reported a new method to reduce the cutting edges radii by etching the surface with a beam of fast argon atoms. The results show that this method allows a minimum depth of cut at a relatively high feed per tooth, however, some issues may be addressed. The current manuscript is unsuitable for publication in Coating.

1. Please show other methods or researches of reducing the radius of the cutting edge in the introduction part.
2. Some of the figure notes are unclear and different from the text, such as Figure 4 and Figure 9.
3. Please check the value in Line 129 and that in Table 3.
4. If necessary, please show more figures about wear measurement.
5. The English language should be polished for better clarity and readability, there are lots of grammatical mistakes and unclear statements in this manuscript.

Author Response

Response to Reviewer 1

1. Please, show other methods or researches of reducing the radius of the cutting edge in the introduction part.

On your advice, we included in the introduction part of the revised manuscript the results of E. Uhlmann et al from the Institute for Machine Tools and Factory Management, Technische Universität Berlin [27]. They experimentally investigated formation of the cutting edge geometry during an immersed tumbling process. During the experiments cutting edge radii in the range of 4.0–31.2 μm were manufactured. It was found that the processing time is mainly responsible for the size of the cutting edge radius. The lapping medium defines the chipping of the edge. Another method for diminishing the cutting edge radius based on the ELID (electrolytic in-process dressing) technique allows manufacturing of cutters with the radius of about 3 μm [37]. However, it cannot be applied for small-sized tools.

2. Some of the figure notes are unclear and different from the text, such as Figure 4 and 9.

We guess you mean Figure 5, not Figure 4. Anyway, we attentively compared the data in the text and in the captions and found no discrepancies.

3. Please, check the value in Line 129 and that in Table 3.

Here you are perfectly right!

In Line 129 is misprinted “9.5 mm” instead of the right value of “10.5” in Table 3.

We made this correction in the revised manuscript.

4. If necessary, please show more figures about wear measurement.

The wear measurement was beyond the scope of our research.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript entitled "Combined processing of micro cutters using a beam of fast argon atoms in plasma" presents a novel method for the coating process of micro cutting tools without a subsequent increase of their cutting edge radius. This work is very interesting and deals with a promising method for processing cutting tools for micromachining applications. Thus, it can be published after several modifications are conducted in the manuscript.

In the Introduction section, the authors should describe some of the included references in more details. More specifically, instead of just referring to a number of references e.g. [15-22], the authors should mention briefly some important details about each paper. Furthermore, the authors should explain which are the minimum coating thickness values obtained with the most important existing methods in respect to the cutting edge radius values of common micro cutting tools.

In section 2, the authors should add a proper flowchart in order to describe fully the complete experimental process of the present work. In lines 328-9 the authors state that "The micro-milling process ... varied orthogonal micro-cutting in the time domain." This statement should be supported by references. In line 353, the authors refer to "forces in the ploughing-dominated region"; they should specify how were these forces calculated and whether they were experimentally validated. If there were some experiments conducted, more details should be definitely presented. Similarly, the third conclusion should be properly modified in order to clarify whether the statement regarding cutting forces and vibration is related to experimental findings or whether it is found in the relevant literature. 

Author Response

Response to Reviewer 2

1. In the Introduction section, the authors should describe some of the included references in more details. More specifically, instead of just referring to a number of references e.g. [15-22], the authors should mention briefly some important details about each paper.

On your advice, we disclosed in the revised manuscript the distinctive features of all references from [15] to [22]. All of them relate to micro particles emitted by cathode spots of the vacuum arc and methods for filtering them:

“An overview of filtered vacuum arc deposition systems based on magnetic ducts is presented in [15]. The droplets can be also removed from the plasma by transformation of radial plasma streams emitted by the arc cathode spots on the side surface of a cylindrical cathode into an axial stream by means of “single bottle neck” magnetic field [16]. Filtered vacuum arc with ion-species-selective bias has been applied to the synthesis of metal-doped diamond-like carbon films [17]. A magnetic island filter comprising three external coils, which generate a uniform magnetic field, and an internal coaxial coil with a cylindrical permanent magnet in its core, placed within the magnetic island, that generate a field in the opposite direction to the external field is described in [18]. Instead of coils, an internal curvilinear spiral was used in [19], which was transparent and allowed observation of the plasma movement from the arc cathode to the substrate. Analysis of the workpiece surface in [20] revealed that its roughness and the number of cathode spots show no direct relation because the current density per cathode spot does not change according to the number of cathode spots. In a pulsed vacuum arc discharge the micro particles can be charged and a roughly quadratic dependence of particle charge on the particle diameter was observed in [21] with a 1-μm-diameter particle having a positive charge of ~1000 electronic charges and a 5-μm-diameter particle having a charge of ~25 000 electronic charges. Highly adherent CrN films were magnetron sputter deposited in [22] after the filtered cathodic arc etching pretreatment.”

2. Furthermore, the authors should explain which are the minimum coating thickness values obtained with the most important existing methods in respect to the cutting edge radius values of common micro cutting tools.

As to the minimum coating thickness values, it should be mentioned that there is no low limit for the wear-resistant coating thickness. It is written in Line 34 of our manuscript “the thicker the coating the longer is its useful life” and, hence, the useful life of coated tool. However, “the only way to increase the useful life of micro cutters without losing the cutting process stability in conditions of parametric tool failure is to reduce the cutting edge radius” (Lines 64-66). For this reason, we decided to sharpen the micro cutters as much as possible before the coating deposition. Previously the minimum cutting edge radius of 4 mm was obtained using an immersed tumbling process in [27]. To more diminish the cutting edge radius we used sputtering of the tool surface with a beam of fast argon atoms.

3 In section 2, the authors should add a proper flowchart in order to describe fully the complete experimental process of the present work.

At the end of the section 2, we added the following list of the experimental process stages.

“The complete experimental process of the present work comprises:

1. Measurement of cutting edge radii, geometry and roughness of micro cutters.
2. Etching the micro cutters to reduce their cutting edge radii.
3. Measurement of the cutting edge radii after the etching.
4. Measurement of the geometry and roughness of micro cutters after the etching.
5. Deposition of a wear-resistant coatings.
6. Final measurement of the cutting edge radii of coated micro cutters.”

 

4. In lines 328-9 the authors state "The micro-milling process ... varied orthogonal micro-cutting in the time domain." This statement should be supported by references.

In the revised manuscript, we supported this statement by references [63, 64].

 

5 In line 353, the authors refer to "forces in the ploughing-dominated region"; they should specify how were these forces calculated and whether they were experimentally validated. If there were some experiments conducted, more details should be definitely presented.

These forces were determined on the base of ref. [65, 66]. Experimental proof is not required, since there is a reduction in plunging forces and resistance to elastic deformation of the cutting edge when plunging into the material.

 

6. Similarly, the third conclusion should be properly modified in order to clarify whether the statement regarding cutting forces and vibration is related to experimental findings or whether it is found in the relevant literature.

As we did not carry out experimental research of vibrations, the third conclusion is properly modified.

Author Response File: Author Response.docx

Reviewer 3 Report

Simple idea, high quality experimental work, but:

„While studying the bombardment by a beam of fast argon atoms, it is necessary to compare the initial geometric parameters of the cutting tools with the parameters obtained after processing.“

„A further increase in the etching time had no benefit for the tool sharpening. It should be mentioned that after quite long etching of the end mills no significant increase in the surface roughness has been observed.“

The goal of quality surfaces/coatings is mainly to reduce wear and increase tool life, it is really necessary to continue research in a wider collaboration, because today there are very accurate models for calculations of wear and tool life, which are suitable for verifying and defending the purpose of this presented method.

Author Response

Response to Reviewer 3

Thank you for the appreciation of our work.

You are perfectly right.

We shall continue the research in a wider collaboration trying to use all available models for calculations of wear and tool life, which are suitable for verifying and defending the purpose of our research.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The author revised all the questions, the manuscript can be accepted now.

Reviewer 2 Report

The authors have performed all the necessary changes to their manuscript. Thus, it is recommended for publication.