3D Printing of Objects with Continuous Spatial Paths by a Multi-Axis Robotic FFF Platform
Round 1
Reviewer 1 Report
The article provided a new insight on the use multi-axis robotic arm for extrusion-based 3D printing. The article focus is to establish a background to explain current techniques for increasing DOF in 3D printing and then introduce the proposed synchronized material extrusion and testing its outcome. The article structure is quiet unusual; utilizing three full sections for introduction and then the last two sections present experimental work and results. In this sense the article fails to distinguish its type (either a research article where the main focus should be experimental, results and discussion, or perspective where a heavier emphasis on the future directions of the field and general overview is missing). The article need to be reorganized in order to have a common theme (research article or perspective). In addition, several issues have to be addressed including:
- Introduction has to emphasize that it is mostly directed towards extrusion-based 3D printing. The manuscript has to mention that other types of 3D printing may not share the same limitations as extrusion-based printers (see for example “Sensors 2020, 20(16), 4514”).
- Introduction (related work section) tend to enumerate previous work without providing any general overview of the field, limitations and/or advantages.
- Most of the figures lack proper labelling and captions. For example Figure 1 caption does not provide any useful description of the work framework, similarly, captions of figures 2-14. Proper labelling is also missing for all the figures.
- the experimental section (6) does not include useful discussion where the article should compare the performance of the proposed technique to previous reports of multi-axis robot (including resolution, tensile strength, reproducibly, …etc.)
Author Response
Thank you very much for your valuable advice. The revised manuscript is attached.
Point 1: The article structure is quiet unusual; utilizing three full sections for introduction and then the last two sections present experimental work and results. In this sense the article fails to distinguish its type (either a research article where the main focus should be experimental, results and discussion, or perspective where a heavier emphasis on the future directions of the field and general overview is missing). The article need to be reorganized in order to have a common theme (research article or perspective).
Response: Thanks for your valuable and patient suggestion. Our initial version of the paper focused on the design of process methods and the corresponding algorithms, and now we have recognized the article. section 3, section 4, and section 5 have been merged into one section to simplify the structure of the paper. Therefore, Path planning methods, platform setup, and controls are all placed in the Methodology section to clarify the whole process.
Point 2: Introduction has to emphasize that it is mostly directed towards extrusion-based 3D printing. The manuscript has to mention that other types of 3D printing may not share the same limitations as extrusion-based printers (see for example "Sensors 2020, 20(16), 4514").
Response: Thanks for the suggestions. Yes, this paper is focused on FDM/FFF and not on all AM equipment mentioned in the literature “3D-Printed Immunosensor Arrays for Cancer Diagnostics”. We have updated the description in section 1. The manuscript makes it clear that our method is related to FDM/FFF, adds more expressions about FDM, and emphasized that the apparent anisotropy of FDM limits the strength of the parts.
Point 3: Introduction (related work section) tend to enumerate previous work without providing any general overview of the field, limitations and/or advantages.
Response: Thanks for the kind suggestion. We added comments and summaries of the relevant work, put forward the problems that need to be solved in section 1 paragraph 3, and describe the objectives of our work in section 1 paragraph 4.
Point 4: Most of the figures lack proper labelling and captions. For example Figure 1 caption does not provide any useful description of the work framework, similarly, captions of figures 2-14. Proper labelling is also missing for all the figures.
Response: Thanks for the questions. We have updated descriptions for figures 1-14. In addition to the references in the text, more detailes are added to the captions of each figure to make it can be self-explanatory.
Point 5: The experimental section (6) does not include useful discussion where the article should compare the performance of the proposed technique to previous reports of multi-axis robot (including resolution, tensile strength, reproducibly, …etc.)
Response: Thanks for the questions. The section 4.3 have been revised. The result shows that our method avoids the strength decrease caused by anisot-ropy. In the discussion section, we added the comparison with related works about surface quality and strength.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript "Spatial Continuous 3D printing based on Multi-Axis Robot" present works toward employment of robotic arm to perform 3D printing. Advantage of the robotic arm in spatial control gives the system benefit of increasing surface quality and tensile strength.
The idea of the manuscript is good. However, there are some concerns of reviewer as follows:
- What is the printing method that this paper focuses on? The printing quality indeed depends on technology employed, but thereis no mention on it neither on the tittle or the abstract.
- So,what is the main contribution of the manuscript, is this the algorithm for path planning? If so, what is the main idea of the algorithm?
- Introduction, Page 1, 1stparagraph: authors wrote that one problem of the conventional printing technique is overhanging structure that needs support. However, in later experiments, author also use support during printing. Could you provide justifications for this?
- Section 2.2: authors reviewed many robotic based printing systems, but what is the difference between them andthis manuscript?
- How do authors consider effect of gravity when the angle of thenozzle is not vertical? Also, will the printing precision be affected due to the gravitational force exerting to melted polymer.
- Figure 2: can you be more specific? Like what is this you are trying to describe, what is the main parts, how do they work?
- Whatare the parameters for the printing, such as temperature, nozzle speeds? Do those parameters have any effect to mechanical properties of the printed parts?
- Conclusion: authors claim that the proposed printing method has better surface quality than traditional printing. However, reviewer could not find any evidence for this conclusion from the manuscript.
Author Response
Thank you very much for your valuable advice. The revised manuscript is attached.
Point 1: What is the printing method that this paper focuses on? The printing quality indeed depends on technology employed, but thereis no mention on it neither on the tittle or the abstract.
Response: Thanks for the suggestion. Our method focuses on FDM/FFF. We highlighted it in the article and added relevant descriptions.
Point 2: So,what is the main contribution of the manuscript, is this the algorithm for path planning? If so, what is the main idea of the algorithm?
Response: Thanks for the questions. We believe that the contribution of this paper can be divided into two parts: proposed a multi-degree-of-freedom continuous path generation method, and presented a universal control structure of the robot printing platform. As for the algorithm, the main idea also includes two steps: the curved layers generation (chapter: Curve slicing) and the path filling between layers (chapter: Global continuous toolpath planning). Compared to the current work, we propose a common reference scheme for multi-axis robotic arms-based 3D printing, which can be used for printing any structure.
Point 3: Introduction, Page 1, 1stparagraph: authors wrote that one problem of the conventional printing technique is overhanging structure that needs support. However, in later experiments, author also use support during printing. Could you provide justifications for this?
Response: Thanks for the question. Yes, sorry for the redundant description. When a support-free path plan strategy is used our approach can remove support, as shown in the following figure. However, in this paper we are focus on improving the strength and surface quality rather than a support-free strategy, so we have removed the redundant description in this version.
Point 4: Section 2.2: authors reviewed many robotic based printing systems, but what is the difference between them and this manuscript?
Response: Thanks for the question. First, the primary goal of most DOF printing methods is to print without support. They are usually concerned with manufacturability, not the mechanical properties of the parts considered in this article. Second, the surface quality of the parts printed by many robotic arms is not ideal because the printing layer is usually not distributed according to the surface of the part. Finally, many articles briefly describe the platform construction process, but this paper gives a more specific construction scheme and control method. And this method can be easily applied to different robotic arm platforms.
Point 5: How do authors consider effect of gravity when the angle of thenozzle is not vertical? Also, will the printing precision be affected due to the gravitational force exerting to melted polymer.
Response: Thanks for the nice question. In our method the gravity effect on printing is almost negligible. Thermoplastic materials have a high viscosity and can be cooled quickly after printing. At the same time, the position of the nozzle is accurate because the robot is controlled through a closed loop.
In addition, we found the description of Curve slicing may be misleading. The flatten threshold (45°) is determined by manufacturability but not the effect of gravity. We have revised these statements in section 3.2.1.
Point 6: Figure 2: can you be more specific? Like what is this you are trying to describe, what is the main parts, how do they work?
Response: Thanks for your guidance. Figure 2 was revised in this version. The structure diagram is drawn, and its working process is briefly described.
Point 7: What are the parameters for the printing, such as temperature, nozzle speeds? Do those parameters have any effect to mechanical properties of the printed parts?
Response: Thanks for the valuable advice. We have added the print settings in the experiment section 4.1. Some parameters are derived from conventional 3D printing and related work.
Point 8: Conclusion: authors claim that the proposed printing method has better surface quality than traditional printing. However, reviewer could not find any evidence for this conclusion from the manuscript.
Response: Thanks for the sugestion. Compared with other robot printing methods, our slicing method has better surface quality on the curved surface. Compared with ordinary FDM, our method avoids the effect of ladder effect on the surface. We have added relevant comparisons in the discussion section 4.3.
Reviewer 3 Report
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Reviewer remarks to the article:
Spatial Continuous 3D Printing based on Multi-Axis Robot
This paper is well constructed. The results of investigations are valuable and very interesting from the point of view of the Additive Manufacturing development. This is the correct planned and done scientific work. The authors applied a methodical apparatus adequate to the assumed goals. But the following comments should be addressed before considering of publication:
1) Abstract could be slightly changed. This abstract is not very detailed. The abstract is expected to include a brief digest of the research, that is - new methods, results, concepts and conclusions only. The abstract needs to be more focused and achievements should be clearly mentioned. Should be brief but should contain the key parts of the paper background and research gaps identification research approach/method, results and conclusions. Must underline the scientific novelty/claim of the paper. Should not be a re-statement of the conclusions. 2) There are some typographical errors. 3) In many cases no space between value and unit, for example: there is 75mm when should it be 75 mm. 4) In my opinion, Conclusions are somehow simplistic as it seems to be observational without revealing findings of generic academic value. What I mean that based on the results some generic and fundamental academic conclusions need to be drawn. In Conclusions, please try to emphasise the novelty, put some quantifications and comment on the limitations. The conclusions should also highlight the progress in understanding of knowledge presented in the work. 5) Please emphasize more, what are the specific conclusions useful for workshop practice. |
Author Response
Point 1: Abstract could be slightly changed. This abstract is not very detailed. The abstract is expected to include a brief digest of the research, that is - new methods, results, concepts and conclusions only. The abstract needs to be more focused and achievements should be clearly mentioned. Should be brief but should contain the key parts of the paper background and research gaps identification research approach/method, results and conclusions. Must underline the scientific novelty/claim of the paper. Should not be a re-statement of the conclusions.
Response: Thanks for your detailed suggestions. We have revised and expanded the Abstract section. In the abstract, we pointed out the problems that need to be solved, introduced our methods, work and results, and revised the overall framework.
Point 2: There are some typographical errors.
Response: Thanks for the reminder. We have rechecked the article and revised the typographical errors.
Point 3: In many cases no space between value and unit, for example: there is 75mm when should it be 75 mm.
Response: Sorry for the wrong format. We have reformated the article according to the Instructions for Authors.
Point 4: In my opinion, Conclusions are somehow simplistic as it seems to be observational without revealing findings of generic academic value. What I mean that based on the results some generic and fundamental academic conclusions need to be drawn. In Conclusions, please try to emphasise the novelty, put some quantifications and comment on the limitations. The conclusions should also highlight the progress in understanding of knowledge presented in the work.
Response: Thank you for your valuable advice. We enhanced the conclusion by adding more content. We emphasized the advantages and characteristics of our method and then extended the limitations of the method. In addition, we have added comparisons with relevant work in the discussion section.
Point 5: Please emphasize more, what are the specific conclusions useful for workshop practice.
Response: Thanks for the suggestion. The revised version provides a detailed platform construction and control method based on the common open-source architecture. At the production stage, this method can be used in the aerospace field, where parts usually need to be lightweight and have high strength. These have been added to the part of the abstract, introduction, and discussion of this article, respectively.
Round 2
Reviewer 1 Report
The manuscript has been updated to address most of the previously raised concerns. Few minor revisions are required k
Title has to be recasted to reflect that this is only towards extrusion-based 3D printing
Some figures can be moved to SI file, for example fig. 8, 11, 13
Author Response
Thank you very much for your approval.
The title has been changed to add the keyword FFF.
Some images and data may be added to the SI for later consideration.
If you have any suggestion, please do not hesitate to point it out. Thank you.
The Word file has been uploaded to the attachment.
Author Response File: Author Response.docx
Reviewer 2 Report
Reviewer failed to find revision made in the attached manuscript. There is no highlight for the change which create a lot of trouble for reviewer to read the revised manuscript. In fact, I could not find any thing news on the revised manuscript and could not give any further comment or suggestion.
Please be serious with academic submission.
Please check the revised manuscript and submit again.
Author Response
I would like to offer a sincere apology for our mistake.
Now the manuscript doc file has been added to the attachment for your review. All changes have been highlighted.
If you have any questions, please do not hesitate to contact us. We sincerely look forward to your valuable comments.
Author Response File: Author Response.docx
Round 3
Reviewer 2 Report
Reviewer has check through the revised version of the manuscript and found it could be recommended for publication.
