Multi-Response Optimization of Ti6Al4V Support Structures for Laser Powder Bed Fusion Systems
Round 1
Reviewer 1 Report
The current manuscript investigates the response of different metal support structures of Ti64 parts fabricated using selective laser melting. The title is highly recommended, and the presented results are very interesting. However, some issues should be considered as follows:
- The abstract should be adjusted, and the concluded results details should be moved to the conclusion section.
- References should be added to support the data presented in the first paragraph of the introduction section.
- In subsection 2-2; it is recommended to define the constant parameters through the text, and to display them in a separate table.
- The powder morphology and the chemical composition of the Ti64 powder should be included.
- The ANOVA results in tables 3, 5, and 7 should be focused, please display only the significant data in these tables.
- The figures' resolution needs to be improved.
- Subsection 3-5 should compare the current study observations to those obtained from the literature and fabricating using the SLM process not the EBM process. This will strengthen and justify the current study analysis and results.
- What about the effect of support structure effect on the surface roughness of the fabricated parts? that might be required to illustrate the impact of the current study.
- There is a lack of references in the introduction and discussion sections.
- In general, please try to avoid redundancy, the presented data should be associative, and focused, and long sentences and paragraphs are not recommended.
Author Response
Dear reviewer,
Thank you so much for your feedback. Below you will find our replies to your comments as well as the revised manuscript with the revisions marked in red. Significant revisions regarding the English language and style will be completed after the MDPI's English editing. The final revised manuscript will be uploaded afterwards on the respective platform.
Response to Reviewer 1 Comments
Point 1: The abstract should be adjusted, and the concluded results details should be moved to the conclusion section.
Response 1: Based on the MDPI template, the way we approached the abstract is the following. i) a brief introduction on LPBF process and supports generation highlighting the purpose of the research, ii) the methodologies that were used to investigate and solve the problem, and iii) the conclusion, summarizing the main findings. We moved the detailed findings to the conclusion section as you proposed replacing those in the abstract with a more general approach and without recording numeric values.
Point 2: References should be added to support the data presented in the first paragraph of the introduction section.
Response 2: References added. (see also point 9 below)
Point 3: In subsection 2-2; it is recommended to define the constant parameters through the text, and to display them in a separate table.
Response 3: Constant parameters table added.
Point 4: The powder morphology and the chemical composition of the Ti64 powder should be included.
Response 4: Powder chemical composition added.
Point 5: The ANOVA results in tables 3, 5, and 7 should be focused, please display only the significant data in these tables.
Response 5: Regarding those tables, all the displayed data are very significant and, in our opinion, should all be presented. F and p values imply the significance of the model in total and in model terms separately. On the other hand, Sum of squares and Mean Square illustrate the effect of each model term in the model. However, the df value could be excluded from those tables.
Point 6: The figures' resolution needs to be improved.
Response 6: All images are of maximum quality at 300 ppi apart from those taken as screenshots directly from the Design-Expert 13 software. Due to the journal’s template, those figures cannot be scaled to their maximum size and some info seems a bit smaller than the original size. We will import them as a TIF format if it makes any difference. Otherwise, they should be scaled up, beyond the template limits. During the English revision, all the figures will be edited to achieve their max quality.
Point 7: Subsection 3-5 should compare the current study observations to those obtained from the literature and fabricating using the SLM process not the EBM process. This will strengthen and justify the current study analysis and results)
Response 7: The aim of this subsection was to compare the archived results with prior published work on both LPBF/SLM and different AM processes. New content and more references have been added here focusing more on comparisons regarding the SLM technology.
Point 8: What about the effect of support structure effect on the surface roughness of the fabricated parts? that might be required to illustrate the impact of the current study.
Response 8: In this research, surface roughness was taken into consideration only as a post processing activity (after the support removal) to evaluate the removal effort and classify the specimens by condition 1, 2 or 3. For rough surfaces with support remnants on them, it took more time and effort to be removed (condition 2) while clear and smooth surfaces (condition 1) considered as “approved” without further post-processing. Roughness measurements and relevant experiments will be considered for future work.
Point 9: There is a lack of references in the introduction and discussion sections.
Response 9: More references were added to both the introduction section and the 3.5 section of the Results and Discussion. Regarding the overall cited references, all the relevant published work done by the researches over the past years has been recorded. However, similar and recent research work has been done only for EBM. In this research, for the first, optimised support structures for SLM are investigated, based on methodologies such as multi-response optimization and design of experiments for both support and AM process parameters.
Point 10: In general, please try to avoid redundancy, the presented data should be associative, and focused, and long sentences and paragraphs are not recommended.
Response 10: It will be considered during the final revised version and English editing.
Kind regards,
Antonios Dimopoulos
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This research work in the manuscript involves a topic about multi-response optimization of metal support structures for laser powder bed fusion systems, and the related work is very meaningful. The manuscript can be accepted after revision as follows.
(1) The abstract should be consisted of the purpose, methods, results and conclusion of the work.
(2) There are many typos and casual English throughout this paper. A professional language is suggested.
(3) Introduction part of the paper is not written properly.
(4) Abbreviations should be given at the first appearance in the paper.
Author Response
Dear reviewer,
Thank you so much for your feedback. Below you will find our replies to your comments as well as the revised manuscript with the revisions marked in red. Significant revisions regarding the English language and style will be completed after the MDPI's English editing. The final revised manuscript will be uploaded afterwards on the respective platform.
Response to Reviewer 2 Comments
Point 1: The abstract should be consisted of the purpose, methods, results and conclusion of the work.
Response 1: Based on the MDPI template, the way we approached the abstract is the following. i) a brief introduction on LPBF process and supports generation highlighting the purpose of the research, ii) the methodologies that were used to investigate and solve the problem, and iii) the conclusion, summarizing the main findings. We moved the detailed findings to the conclusion section replacing those in the abstract with a more general approach and without recording numeric values. Is there anything else that could be deleted or removed to another section?
Point 2: There are many typos and casual English throughout this paper. A professional language is suggested.
Response 2: The revised version will be sent for English editing.
Point 3: Introduction part of the paper is not written properly.
Response 3: The introduction section has been also written according to the MDPI template which is based on 3 main parts. It defines the purpose of the work and its significance, the current state of the art followed by relevant references, as well as the aim and the expectations of the research. Is there anything that missing or should be removed from this section?
Point 4: Abbreviations should be given at the first appearance in the paper.
Response 4: All abbreviations have been revised.
Kind regards,
Antonios Dimopoulos
Author Response File: Author Response.pdf
Reviewer 3 Report
What is the innovation factor of this article when compared to the literature?
What are these traditional methods? Line 35
About Table 1. What were the resolution (dots per square inch) and number of cycles of laser irradiation?
Why did only the laser speed (mm/s) change in the experiments ( level 1, level 2 and level 3?
Author Response
Dear reviewer,
Thank you so much for your feedback. Below you will find our replies to your comments as well as the revised manuscript with the revisions marked in red. Significant revisions regarding the English language and style will be completed after the MDPI's English editing. The final revised manuscript will be uploaded afterwards on the respective platform.
Response to Reviewer 3 Comments
Point 1: What is the innovation factor of this article when compared to the literature?
Response 1: The innovation factor compared to the literature concerns the investigation of an innovative design approach for effortless, reliable, and sustainable AM, towards the future research and development of a platform capable of proposing optimized support structures according to part’s geometry. In this research for the first time, optimised supports for LPBF that are easy to remove and consume the minimum support material without affecting the quality of the part were investigated. The optimization approach focuses on the evaluation of the various support and process parameters by using design of experiments methodology and relevant optimization algorithms. Similar work has been done only for EBM technology.
Point 2: What are these traditional methods? Line 35
Response 2: Traditional methods such as machining, molding, forming, etc.
Point 3: About Table 1. What were the resolution (dots per square inch) and number of cycles of laser irradiation?
Response 3: Two of the most important features regarding the laser parameters given by the manufacturer are the Yb-fiber laser of 400 W and the focus diameter of 100 μm. Furthermore, F-theta lens and high-speed scanner characterize the precision optics. DPI settings and laser irradiation are not provided by the manufacturer. We would appreciate any references that could help. The above-mentioned features have been added to the content.
Point 4: Why did only the laser speed (mm/s) change in the experiments (level 1, level 2 and level 3?
Response 4: During the screening experiments laser power was also included as an input variable. However, the combination of laser power and laser speed with the various support parameters resulted in many printing defects and failures. This happened because the numerical range of laser speed and laser power was very unpredictable and difficult to be defined. High speed with low power had as a result collapsed parts, while low speed with high power had as a result strong supports, impossible to be removed. For that reason, we decided to keep laser power constant and change only the energy input based on varying the laser speed. Future research includes the investigation of both laser speed and laser power (and other laser parameters) without considering the support parameters.
Kind regards,
Antonios Dimopoulos
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The revised manuscript is improved. All the review comments and recommendations are well addressed. However, as a minor issue; the recommended approach is experimentally validated for the Ti64 Grade 5 parts, the title should be related to that material or the effect of density variation from material to another should be considered in the discussion.
Author Response
Dear reviewer,
Thank you so much for the feedback.
The title has been changed as follows:
"Multi-Response Optimization of Ti6Al4V Support Structures for Laser Powder Bed Fusion Systems"
Kind Regards,
Antonios Dimopoulos
Author Response File: Author Response.pdf
Reviewer 3 Report
what are the future steps of work?Author Response
Dear reviewer,
Thank you so much for the feedback.
The last paragraph regarding the future steps of work has been improved, describing in a more in-detailed way the directions that will be investigated.
Specifically, these are:
- The exploration of new support structure geometries.
- The generalisation of the methodology to include more materials, a variety of part sizes and complexities.
- The development of a web application to facilitate independent decision workflows for support design and generation.
Kind regards,
Antonios Dimopoulos
Author Response File: Author Response.pdf
