Advancements in 3D Printing: Directed Energy Deposition Techniques, Defect Analysis, and Quality Monitoring

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The Manuscript deals with a comprehensive SoA of DED in terms of technology, defect generation, monitoring and simulation.

The Manuscript is well-structured. Nevertheless, some flaws have been detected and they need to be solved for Manuscript publishing.

·        A Nomenclature section is strongly recommended before Introduction.

·        In the Abstract, no acronyms should be used.

·        Once an acronym has been defined (e.g., Additive Manufacturing (AM), Direct Energy Deposition (DED), etc.), only the acronym should be used in the text. Please, improve it.

·        Terms as Additive Manufacturing, Computer-Aided Design and every word represented by an acronym should show the first letters in capital letters. Moreover, the acronyms should be in capitol letters. Please, improve it.

·        Page 2, “(AM) sector is expected to grow at an annual rate of 22% from a USD 15 billion industry in 2020 [5].” Since we are in 2024, please provide more up-to-date data.

·        Page 3, the sentence “AM offers a significant advantage in its ability to produce multiple components simultaneously, re” is not clear. Do you refer to production volume or to the opportunity to print different shapes in the same job? Please, clarify it in the text.

·        Page 3, “For instance, manufacturing an entire jet engine…………on typical supply chains.”. Here the Authors are describing the consolidation enabled by AM, but there is no reference to consolidation. Please, make it explicit.

·        Page 3, “The narratives surrounding the technological shift towards the rapid AM development have been made possible by significant cost reductions, the expiration of earlier patents, and the re-licensing of many laser and optics systems over the last two decades”. An important reference dealing with this topic is reported in DOI: 10.1002/9781119513957.ch12. Please, add this reference into the document.

·        Page 4, “This step is essential for DED technology because, unlike Powder Bed Fusion (PBF), it does not require any support structures.”. This depends on the type of system being deployed. A 2½-axis or 3-axis DED is constrained in terms of achievable geometric complexity. This should be clearly stated in the text.

·        Figure 2. Some writings in the figure are not well aligned.

·        Page 5. “Additionally, other environmental factors such as carrier and shielding gases, plasma distribution, spatters, and whether the atmosphere is opened or closed are often latent variables that require monitoring.”. A reference deeply highlighting this topic is DOI10.3390/app10124212. It could support the argumentation.

·        Page 5, “Even if the same material is used, the process parameters optimized for one part may not yield the same results for another part design [26].”. Here some causes inducing defects should be indicated, such as: geometric variations (thin walls for example), localised hotspots, deposition strategies in terms of laser path, etc.

·        Page 6. Some references supporting the argumentation on post-processing and repairing can be DOI10.1007/s00170-021-08313-7 and DOI: 10.1016/j.procir.2020.01.164. Please, add them if you consider it appropriate.

·        Page 7. Typo error.

·        Page 7, “According to the market share data for 2020 displayed in Fig 3,”. Please, provide more up-to-date data.

·        Page 9, “Moreover, DED offers several advantages over other metal AM technologies, enabling the creation of complex structure geometries without support mechanisms.”. It should be made clear that the geometric complexity achievable by the DED depends on the kinematics of the used system.

·        Page 10, “However, a key difference distinguishes the two processes: welding…”. The lower HEZ of DED compared to welding is also a point of distinction between the two processes. Please, add it.

·        Page 10, the sentence “For instance, wire-DED has the highest build rate compared to powder-DED but with lower feature resolution.” Is repeated twice.

·        Page 12, H/D > 1 also induces lack of fusions between tracks due to the shielding effect of the pre-deposited clad. Please, add it.

·        Figure 5. Please, improve image quality.

·        Page 13,. Some more information concerning the influence of Marangoni convection, vapour plume, recoil effect on melt pool quality should be provided to increase the significance of these phenomena on the final DED print.

·        Page 15. “remains a mystery” is not a suitable expression for a scientific paper.

·        Page 15, “er. Similar observations were made for Inconel 625 [96] and Inconel 718 [79, 99] alloy powders. It has been argued that the amplification of energy is the cause of this phenomenon, with the increment in laser power resulting in radial dissemination of energy emanating from the central locus of the laser beam towards the circumferential peripheries of its diameter”. The sentence is not clear and needs to be improved.

·        Page 19, typo.

·        Page 22, typo.

·        Page 22, Another defect related to non-uniform layer thickness results from the lack of melting for low energy densities (also known as balling in SLM). Please discuss this to complete section 4.1.1.

·        Page 23. There are also destructive tests to characterise samples. Please, add it.

 

·        The spatter phenomenon represented in Figure 8 is realy huge compared to what happens in the real process (spatter balls are two units of magnitude smaller than the melt pool). Please, improve it.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Feedback for authors:

The authors submitted a manuscript entitled „Advancements in 3D Printing: Directed Energy Deposition Techniques, Defect Analysis, and Quality Monitoring“.

The paper has a very well-structured and clear presentation of ideas, but some parts are poorly organized, which can lead to confusion or misunderstanding of key points.

The article makes a significant contribution to the field of scientific research by offering new perspectives and addressing current issues.

The authors presents a comprehensive and logical discussion that provides a coherent view of the meaning and implications of the results.

Some sources are outdated or inaccurate, which reduces the reliability and authority of the article.

The manuscript is well-written, interesting, and can be an inspiration to other scientists.

I have no further recommendations.

Overall, it deserves publication in Technologies.

 

Minor revisions:

There is a paragraph on page 7 that has a different text size.

Some images require better readability of the text, either the text is too small or the quality is insufficient.

Some tables require better alignment for better clarity.

 

 

After correcting minor errors, I recommend publishing the manuscript in the journal Technologies.

Comments on the Quality of English Language

I heave no comments.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This paper provided a comprehensive analysis of recent advancements in additive manufacturing, a transformative approach to industrial production that allows for the layer-by layer construction of complex parts directly from digital models, and reviewed the advancements in 3D printing: directed energy deposition techniques, defect analysis, and quality monitoring. The work of the paper is well-done, with some interesting results. However, it requires an appropriate revision before publication.

1. The paper should analyze the existing problems of the directed energy deposition techniques technology and make further comparison with other processes

2. The focus of this paper is the analysis of the directed energy deposition technology, and the introduction of other processes should be reduced.

3. More images of microstructures and defects are welcome.

4. An appropriate revision in English is needed.

Comments on the Quality of English Language

An appropriate revision in English is needed.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors, 

thank you for implementing all the comments and suggestions. 

The Manuscript can be accepted for publication.