Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

English should undergo proofreading by a native speaker.

The document should consistently adopt a third-person perspective, a meticulous review is necessary to rectify instances of first-person usage.

Why opt for a PLC S7 1200 over a more contemporary alternative?

In the introduction, the authors assert in lines 68 and 69, "The study is based on a classic case study in the industrial domain, specifically the machining process, which involves various uncertainties and numerous process parameters". However, Figure 1 depicts a mock-up of the process rather than an authentic industrial application.

Upon verifying the use of a mock-up instead of a real industrial application, could the PLC have been substituted with a microcontroller, such as a Raspberry Pi, to curtail mock-up construction costs?

The development and design of the digital twin using Unity 3D demand elaboration.

The selection of the Unity 3D graphics engine is not expounded upon; why was it chosen over alternative engines like Unreal?

The virtual environment generated by the aforementioned graphics engine lacks appeal. It would be advantageous to position the proposed machine in an industrial setting rather than an empty space, as depicted in Figure 5. The authors assert their engagement with a digital twin in an industrial environment; therefore, the developed environments should align with this assertion.

Figures 10 and 11, in my assessment, do not significantly contribute to the comprehension of the project's progression and are recommended for elimination.

The visual quality of Figure 14 should be enhanced.

Comments on the Quality of English Language

Minor editing of English language required

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have presented a well-written and engaging paper.

In this research paper, the authors developed a digital twin system that seamlessly integrates process parameter simulation solutions for typical machining processes in the realm of intelligent manufacturing.

The conclusions drawn in the paper are adequately supported by experimental data.

However, I have a doubt, on one hand, the authors emphasize that the good accuracy of their calculations and experimental results. On the other hand, they suggest that the accuracy is limited, due to budgetary reasons.

It would be preferable for the authors to explicitly assess the accuracy of the existing model using appropriate metrics and make meaningful comparisons with other relevant research in the field.

 

Regarding the minor revisions:

Line #70: there is a capitalization error.

Figure #16 on page 14: The titles of the axes are missing.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The presented DT architecture in the framework is interesting as it can contribute to efficient real time monitoring and control of machining processes using a combination of simulation tools with DT capabilities provided by Unity software and FEM modeling.

In the introduction some references are provided on state of art works related to Digital twins as well as there limitations are identified however it cannot be seen clearly how the presented framework can contribute to solve the issues with existing DT models discussed.

Its not clear how the FEM model was developed and the contribution of it within the whole framework.

In the discussion section limitations of the proposed DT architecture are highlighted however it is not compared to existing works that provide the same features.

Comments on the Quality of English Language

   

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The paper presents a prototype digital twin (DT) system for monitoring and optimizing a machining process. The DT integrates data from the machining equipment and the workpiece to enable real-time visualization, control, and simulation.

The system has three main components - the physical twin (actual machining setup), virtual twin (Unity 3D models), and ANSYS simulation module. It achieves two-way communication between the physical and virtual components via PLC data transfer.

Experiments demonstrate satisfactory real-time control and monitoring capabilities of the system. However, limitations exist due to budget constraints affecting sensor accuracy and computational complexities reducing simulation synchronization rates.

Future work will focus on simplifying the ANSYS finite element models and enhancing computational efficiency through techniques like model reduction, grid optimization, and parallel computing. This is expected to improve overall system efficiency for intelligent manufacturing applications.

In summary, the prototype shows promise for machining process monitoring and optimization but requires refinements to the simulation module and computations to fully realize its potential industrial value.

The review of the state of the art appears somewhat superficial, lacking an in-depth exploration of existing DT systems in the context of machining processes. The paper could benefit from a more comprehensive examination of related research, including a detailed analysis of comparable prototypes and their strengths and weaknesses. A deeper understanding of the existing landscape would provide a more robust foundation for highlighting the unique contributions of the proposed prototype.

While the research gap is acknowledged, it is described as relatively small. The paper could enhance its contribution by explicitly delineating the specific aspects of the DT system that distinguish it from previous work. Additionally, a more thorough discussion of the practical implications and potential applications of the proposed system in the context of intelligent manufacturing would strengthen the argument for its significance.

The experiments conducted demonstrate satisfactory real-time control and monitoring capabilities, but the limitations due to budget constraints impacting sensor accuracy and computational complexities affecting simulation synchronization rates are acknowledged. While these limitations are discussed, a more detailed exploration of their potential impact on the overall effectiveness of the system and its practical applicability would provide a clearer picture for readers.

Author Response

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Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

This is a very interesting paper and should be interesting to readers once a few deficiencies are addressed.

1. References are incomplete.  Grieves should be referenced as he describes exactly this sort of system in his papers from 2005 and in particular 2014 (predating Tao).  Qi & Tao give a good overview in their 2022 paper.

2. The overall problem is not clearly stated. The system (production and product) should be adequately explained before the data structure. At the moment it is the other way around & so hard to follow. Also the application context should be explained: What is the purpose of this Twin? Quality in Manufacturing? Teaching? Just research?

3. Further detail on the system setup - sensor error, data transmission and latency… - would be interesting.

4. More detail should be provided on the modeling equations and the methods used for adjusting the models to synchronize the physical and virtual entities. This would be more interesting than the pseudo-code for the UI. The UI Pseudocode does not seem important - please indicate why it is critical or delete.

5. Why do you separate “simulation” and “virtual”? I see these as 2 aspects of the Digital Twin (Virtual Model / Virtual Entitiy as Tao calls it).

6. You refer in the text to the section “Methodology”, but I do not find it.

Overall I think this is an interesting paper. I encourage the authors to strongly review the paper to ensure that the storyline is clear from the system description, problem (or use case) description, solution and details and then clearer presentation of the results in comparison the the problem/use case requirements. Please also include some of the technical details so that others my build upon your work.

Comments on the Quality of English Language

The English is overall very good, from a grammatical point of view. However there are several minor errors (about 1 per page) which show that a proof reader should be employed to check and correct the final manuscript.

The more serious issue is that the discussion is very indirect. I suggest the authors restructure the paragraphs to make sure that ideas are introduced in a way that the reader will find it easy to follow.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have read the recommendations and have appropriately corrected their document. They have provided technical justification for their decisions.

Author Response

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Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

This version is significantly improved in comparison to the last version. Thank you for your additional explanations and detail.

Comments on the Quality of English Language

In the new text there are some incomplete sentences.  e.g. L445-446 "Due to...limitations."  This seems to be either part of the prior sentence or the one after.  Please employ a professional proof reader to remove such errors.

Author Response

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Author Response File: Author Response.pdf