Model of the Selective Laser Melting Process-Powder Deposition Models in Multistage Multi-Material Simulations

Round 1

Reviewer 1 Report

Reviewer 1#:

In this work, the powder bed generation model is connected to the Lattice Boltzmann Method (LBM) calculation module in the closed circuit. The simulation results of the multistage SLM process with the Ti-6Al-V alloy and bioactive glass are presented in the paper. The simulation results confirm the possibility of modeling several SLM stages with two different materials. Some important results have been obtained. Still, the minor modifications or clarifications should be made before the possible acceptance.

Comment 1: The first time LBM appears in the abstract, it needs to use the full name and explain it.

Comment 2: The Introduction section is very informative, but it is divided into too many paragraphs, so we suggest combining some paragraphs.

Comment 3: Although the Introduction section introduces many simulation methods, there are still some important articles that have not been covered. Hopefully, they will be mentioned in the article.

[1] Shinjo J, Panwisawas C. Digital materials design by thermal-fluid science for multi-metal additive manufacturing[J]. Acta Materialia, 2021, 210: 116825.

[2] Panwisawas C, Qiu C, Anderson M J, et al. Mesoscale modelling of selective laser melting: Thermal fluid dynamics and microstructural evolution[J]. Computational Materials Science, 2017, 126: 479-490.

Comment 4: Did the author consider the problem of powder splash in the SLM process and what effect it has on the model?

Comment 5: There is no scale bar in the picture of the temperature field distribution (Fig.8(a), Fig.(12) , etc.), which is necessary, please add the scale bars.

Comment 6: The figure captions are not very accurate (Fig. 7, 9, 13, etc.). Please expand them.

Comment 7: The author simulated the temperature field distribution and melting process in the SLM process, but there is no comparison with the true temperature distribution, how to judge the accuracy of the model?

Comment 8: Conclusion needs to be more specific and quantitatively.

The language of this paper is good, and can be further improved.

Author Response

Comment 1: The first time LBM appears in the abstract, it needs to use the full name and explain it.

Thanks for the comment. The correction is made.

 

Comment 2: The Introduction section is very informative, but it is divided into too many paragraphs, so we suggest combining some paragraphs.

Thanks for the suggestion. I combine several paragraphs.

 

Comment 3: Although the Introduction section introduces many simulation methods, there are still some important articles that have not been covered. Hopefully, they will be mentioned in the article.

[1] Shinjo J, Panwisawas C. Digital materials design by thermal-fluid science for multi-metal additive manufacturing[J]. Acta Materialia, 2021, 210: 116825.

[2] Panwisawas C, Qiu C, Anderson M J, et al. Mesoscale modelling of selective laser melting: Thermal fluid dynamics and microstructural evolution[J]. Computational Materials Science, 2017, 126: 479-490.

Thanks for the comment and suggestion. The first proposed position was cited in the paper, I extend their description, as well as, I add the second position to the Introduction section.

 

Comment 4: Did the author consider the problem of powder splash in the SLM process and what effect it has on the model?

Thanks for the question. I do not consider the splash in the model. Free surface flow, heat conduction and transfer, convection, evaporation, surface tension, and wettability with hysteresis are the main phenomena considered in the liquid phase in the model.

 

Comment 5: There is no scale bar in the picture of the temperature field distribution (Fig.8(a), Fig.(12) , etc.), which is necessary, please add the scale bars.

Thanks for the comment. I add the temperature scale as Figure 8d, it is the same in the other figures.

 

Comment 6: The figure captions are not very accurate (Fig. 7, 9, 13, etc.). Please expand them.

Thanks for the comment.

Figure captions are changed.

 

Comment 7: The author simulated the temperature field distribution and melting process in the SLM process, but there is no comparison with the true temperature distribution, how to judge the accuracy of the model?

Thanks for the comment.

I do not present verification of the temperature submodel in the paper. The evaluation was fulfilled by comparison of the parameters of the melting pool obtained in simulations with literature data of similar modeling and microstructural studies. Such verification was made by another member of the team and it is not published yet.

 

Comment 8: Conclusion needs to be more specific and quantitatively.

Thanks for the comment.

The Conclusions section was changed.

Reviewer 2 Report

General comment:

the paper proposed a holistic model for full-scale modeling of SLM process for multimaterial printing.

 

Specific comments:

1. page 7, what is levering? is it the action of the recoater or roller to smooth and flatten the top layer? is it the correct term to use to describe the process?

2. the conclusion is too short. suggest highlighting the novelty and limitation of the method and possible future work for further improvement.

3. can the proposed simulation model the evolution of the microstructure of the multi-material printing?

4. multimaterial modeling for pbf has been attempted before. suggest citing:

    a. Tang, C., Yao, L., & Du, H. (2022). Computational framework for the simulation of multi material laser powder bed fusion. International Journal of Heat and Mass Transfer, 191, 122855.

    b. Küng, V. E., Scherr, R., Markl, M., & Körner, C. (2021). Multi-material model for the simulation of powder bed fusion additive manufacturing. Computational Materials Science, 194, 110415.

 

it is generally easy to read.

Author Response

Comment 1: page 7, what is levering? is it the action of the recoater or roller to smooth and flatten the top layer? is it the correct term to use to describe the process?

Thanks for the comment. You are right I used an unfortunate term. Yes, it is smoothing and flattening of the top layer of powder.

 

Comment 2. the conclusion is too short. suggest highlighting the novelty and limitation of the method and possible future work for further improvement.

Thanks for the comment.

The Conclusions section was rewritten and extended.

 

Comment 3. can the proposed simulation model the evolution of the microstructure of the multi-material printing?

Thanks for the comment.

I have more than 10 publications on the modeling of microstructure evolution using frontal cellular automata, including several during solidification. Therefore, I do not see a big problem in adding a module to simulate the microstructure evolution. But now, I do not consider it in this model.

1. Svyetlichnyy, Modeling of macrostructure formation during the solidification by using frontal cellular automata, in Cellular automata innovative modelling for science and engineering / ed. Alejandro Salcido Rijeka : InTech, cop. (2011), https://cdn.intechopen.com/pdfs/15011/InTech-Modeling_of_macrostructure_formation_during_the_solidification_by_using_frontal_cellular_automata.pdf

 

Comment 4. multimaterial modeling for pbf has been attempted before. suggest citing:

122855. Tang, C., Yao, L., & Du, H. (2022). Computational framework for the simulation of multi material laser powder bed fusion. International Journal of Heat and Mass Transfer, 191, 122855.
122856. Küng, V. E., Scherr, R., Markl, M., & Körner, C. (2021). Multi-material model for the simulation of powder bed fusion additive manufacturing. Computational Materials Science, 194, 110415.

I am very grateful for your comment and suggestion I add these publications to the Introduction section.

Reviewer 3 Report

Reviewer comments

In this paper, one of the final stages of the development of a holistic model of the selective laser melting (SLM) process is presented. The lattice Boltzmann method is applied for simulation of laser treatment, melting, fluid flow, and solidification. The holistic model developed by author can be used for simulation, design, and optimization of multistage, multi-material SLM processes. At the same time, this manuscript presented the simulation results of the multistage SLM process with the Ti-6Al-V alloy and bioactive glass. Therefore, it is recommended to receive after minor modification.

1. The introduction of the manuscript spends considerable space discussing numerical simulations of SLM, including various simulation methods, material systems, and research topics. However, this appears to be a simple listing of numerous references and fails to summarize any valuable conclusions

2. In the title of Table 1, I am unsure about the meaning of "300÷1500 ℃." Is it an error in the manuscript or does it have a different significance? Please provide further explanation.

3. In the conclusion section, I noticed that all simulation results related to temperature field distribution (including figures) did not mention specific temperature values, and corresponding scales were absent from these images. This leaves the simulation results less convincing

4. The authors used Ti alloy and bioactive glass particles to simulate a multi-material SLM process. In reality, multi-materials are mixed uniformly before undergoing the SLM process. However, the manuscript used bioactive glass as a separate layer for SLM, which seems inconsistent with the actual SLM process.

5. The innovative content of this manuscript is the implementation of powder spreading processes for multi-layered SLM using particles of different shapes. The authors should discuss the long-term significance and value of this work for SLM technology development in the manuscript.

 

 

 

Author Response

Comment 1: The introduction of the manuscript spends considerable space discussing numerical simulations of SLM, including various simulation methods, material systems, and research topics. However, this appears to be a simple listing of numerous references and fails to summarize any valuable conclusions

Thanks for the comment.

I agree. I change the beginning of the Introduction section to precise the aim of the paper, then describe the state-of-art in the modeling of the SLM process. I also summarize the analysis at the end of the section.

 

2. In the title of Table 1, I am unsure about the meaning of "300÷1500 ℃." Is it an error in the manuscript or does it have a different significance? Please provide further explanation.

Thanks for the comment.

It is an error. It appears when I prepper the Table and it originates from the properties of the glass. The viscosity of the glass in the range of the temperature of 300-1500°C changes in the range of several orders of magnitude. Later I simplified the viscosity model.

 

3. In the conclusion section, I noticed that all simulation results related to temperature field distribution (including figures) did not mention specific temperature values, and corresponding scales were absent from these images. This leaves the simulation results less convincing

Thanks for the comment.

I add the temperature scale in Figure 8d where the temperature is presented in kelvin and dimensionless units, and change the Conclusions section.

 

4. The authors used Ti alloy and bioactive glass particles to simulate a multi-material SLM process. In reality, multi-materials are mixed uniformly before undergoing the SLM process. However, the manuscript used bioactive glass as a separate layer for SLM, which seems inconsistent with the actual SLM process.
5. The innovative content of this manuscript is the implementation of powder spreading processes for multi-layered SLM using particles of different shapes. The authors should discuss the long-term significance and value of this work for SLM technology development in the manuscript.

Thanks for the comment.

I agree, but only in the case when mixed materials are metals, especially when they form an alloy. In the case of such materials as metal and glass (ceramics) when materials have very different properties and should not form alloys and the structure of the product should be accurately controlled because materials play different roles in the product, the mixture before the process cannot be performed. For example, titanium alloy is inert long-term biocompatible, able to perform its intended function without eliciting any undesirable local or systemic effects. Metallic glasses based on magnesium with zinc and calcium addition are biomaterials for biodegradable medical implants. A scaffold or matrix for tissue-engineering products refers to the ability to perform as a substrate that will support the appropriate cellular activity, including the facilitation of molecular and mechanical signaling systems, in order to optimize tissue regeneration, without eliciting any undesirable effects in those cells. One of the technology uses SLM for the creation of a regular metallic matrix or foams with the next coating with bioactive glass. The matrix is dipped into the molten glass or the molten glass is sprayed onto the surface. But both methods have disadvantages, which can be removed in the proposed approach.

I change the Introduction section to partly answer your question.

Round 2

Reviewer 2 Report

The replies are satisfactory. the quality of the manuscript has improved significantly in the revised version.