Optimization of an Air Conditioning Pipes Production Line for the Automotive Industry—A Case Study

Reviewer #1

Comment/Suggestion

Action done

This article, being the result of a comprehensive case study, offers an interesting insight into the combination of Lean methods and the CONWIP system in an industrial context, however, before publication, I recommend making a minor correction.

Thank you for your overall evaluation of our paper and kind words. We have paid particular attention to all Reviewers’ comments and suggestions, trying to improve the paper as much as possible.

The abstract is lengthy and somewhat complex, which might overwhelm a reader seeking a quick grasp of the paper’s objectives and findings. A more concise abstract focusing on key findings and the significance of the research would be beneficial.

Thank you for your suggestion. We have partially rewritten the Abstract, trying to emphasize the main focus of the work and real objectives.

The introduction provides extensive background but could better highlight the specific research gap or problem the study addresses. Authors should succinctly state the research problem and how this study contributes uniquely to the field. While the methodology is thorough, its complexity might limit its applicability in smaller or less resourceful production settings. The study could benefit from a more explicit integration of technology-driven solutions, considering the rapid advancements in industrial automation and data analytics. The study focuses heavily on operational efficiency while potentially underemphasizing other aspects like worker safety, ergonomics, and environmental impact.

Thank you for your comments in these aspects. We tried to highlight the research gap which constituted the main motivation of this work and its novelty. Regarding the methodology, we are afraid that we cannot change it deeply, because it is the core of the work and cannot be changed after the work done. Indeed, the work is not strongly based on technology-driven solutions, but we tried to improve this aspect in the revised version. Moreover, the workers’ safety was also improved in the revised version of this paper.

The methodology seems robust in achieving reliable results, given the systematic approach and iterative improvements based on data analysis. However, external factors such as market fluctuations, supply chain disruptions, or changes in customer demand might affect the generalizability of the results.

Thank you for your comment. Some of your concerns were not considered because they were not felt in the company environment where the work was performed. Thus, maybe we cannot be able to improve this part of the work.

The discussion mixes results and interpretations, which might confuse readers. A clearer distinction between findings and their interpretation or implications would be beneficial. Start with a summary of key findings, followed by a separate analysis of what these findings mean in the context of existing literature.

Thank you for your comment and suggestion. We promoted a better distinction between Results and Interpretations. We tried to follow your suggestions as much as possible.

The conclusions are comprehensive but could more explicitly tie back to the research objectives stated in the introduction.  A more concise summary of how the study meets its initial aims would be useful.

Thank you so much for your comment. We tried to improve the linkage between the main research goals and the conclusions.

Technical notes:

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- line 470 and 472, 506 Error! reference source not found

The authors should thoroughly check the references, as in my opinion, in several places the references have been misplaced and do not pertain to the correct citations.

Thank you so much for your advice. We have carefully checked all these situations, trying to eliminate them. Surely, the final proofread promoted by MDPI will help us to find any mistake we have not detected in the revised version, to make the paper clear of mistakes.

Despite the remarks pointed out, I highly rate the presented case study

Thank you for your time and for your unvaluable help in helping improving our paper with your crucial comments and suggestions.

Reviewer #2

Comment/Suggestion

Action done

I thank the authors for reviewing their study. The article aims to show how a mix of continuous improvement (CI) and Lean tools can reduce waste and process variability along a climate-controlled pipe production (PL) line. The article is comprehensive and well-structured. However, the contents of the sections are sometimes superficial.

Thank you for your overall evaluation of our paper and kind words.

The Background section could be improved by analysing similar studies in the automotive sector. There are several articles that study this issue, and it is important to cite them to further highlight the research gap you intend to fill.

Thank you for your pertinent comment. Most of the references used already are from the automotive sector. However, we have added a couple of references more [27,28] and we have recoved more two references already utilized in the Discussion [25,26] to expand the Background regarding the use of other Lean tools in a different way of that here utilized, following by this way your suggestion. Moreover, as per suggestion of other Reviewer, the Background needed to be compressed.

To date, there are numerous methodologies that use metaheuristic algorithms to identify the best combinations between families. Why is your method more appropriate and efficient? It would be useful to investigate this aspect as well as to report on it in the conclusion section.

Thank you for your pertinent question. The Authors made an additional effort in explaining the reasons behind the selection of this method to perform this study.

You should specify the references in Table 3. Which process do they refer to?

Thank you for your question. The references pointed out in this case are product references, which, due to confidentiality reasons, cannot be revealed. Hope you understand, but, because they are not literature references, we guess the problem is solved.

Check the grammar. Why are some words always capitalized (i.e. Lean)? Check the acronyms (i.e. line 93 Continuous Improvement).

Thank you so much for your suggestions. We have revised all these situations, trying to ‘clean’ the text as much as possible of mistakes and grammatical errors. Usually, in the literature, Lean appears as capitalized, thus, we kept it capitalized. Moreover, we have added the extended name o CI (Continuous Improvement). Thank you so much for your observation.

About the formula 'OEE (%) = D (%) × E (%) × Q (%)'. What are D, E and Q?

Thank you for pointing this out. We have added the meaning of the abbreviations. Our apologies due to the mistake.

In Figure 1, what do WC and TT stand for?

Thank you for pointing this out. As in the previous point, we have corrected the mistake.

In Line 235, you repeat the term 'figure 2' twice.

Thank you so much for your note. The mistake is now corrected.

On lines 470 and 472, 506, there are several 'Error reference not found'.

Thank you for pointing this out. Maybe it was a problem generated by the MDPI system when converting DOCX file to PDF file, regarding the cross references. The problem is now solved.

Reviewer #3

Comment/Suggestion

Action done

I like the case studies that represent the combined application of the methods of a trend. This paper may serve as an example for other companies about how to develop the production system. The structure and the style of the manuscript are acceptable; the authors strived for scientific soundness in each section. I can support the publication of the paper after considering some improvements.

Thank you so much for your overall appreciation of our work and kind words. Obviously, we tried to understand your comments and suggestions, properly addressing them, hoping the improvements are in line with your expectations.

First, the paper is very long. The Background chapter seems to be unnecessary in the present form. It shows some basic descriptions of the tools and methods. It can be compressed and more focused on the reasons for the selection. In other words, it could show a system of the used methods.

We fully agree with the Reviewer. Indeed, our initial intention was to “produce” the paper as much didactic as possible, allowing “beginners” to easily understand the main ideas. However, we have properly compressed the Background and Methods, but conditioned by the Reviewer #1, who asked us to expand the Background.

It is a case study, but the conclusions should offer a broader outlook and include the limitations of the methodology (now it is about the case study).

Thank you for your suggestion. A broader outlook and main limitations of the study have been added in the revised version.

Moreover, I suggest involving more relevant sources.

Thank you for your comment, but it is a little generic and we didn’t understand its focus. Are you asking for more References? Or do you intend that the Discussion should include more comparisons?