Process Optimization and Distortion Prediction in Directed Energy Deposition
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe research paper is interesting and has a good point of view, however, there are several issues before being ready for publishing.
The introduction is lack of references, there are several paragraphs afirming things that they are not addecuately cited, please add the references of this affirmations. Specially in the firsts paragraphs. One example where you can find information is: https://doi.org/10.1007/s40684-020-00302-7
or https://doi.org/10.1007/s40684-020-00302-7
among others.
Please, explain the geometry description, the numbers selected for the layers are obtained from experiments? THe height is remarcably precise with 4 significant digits, please explain.
Figure 5 and the method for printing layers is not clear, it generates the clad tracks alternative? Only go to the right? The figure and the explanation is confusing.
You detail the thermal properties until 870º, but the mateiral using DED is melted, so the original temperature should be from at least this temperature, around 1500ºC, did you consider this fact?
Line 339, it is called molten pool, not pool of melt. Also, the heat source do not only fuses the powder but also the substrate, or previous layers, you can have here a text where in the introduction this part is well explained: https://www.mdpi.com/2075-4701/10/10/1291
In model validation you mention different printing strategies, but it is not clear in the materials and methods. Please explain in the constitutive model what strategies will be performed.
What is the time of each layer? In the graphs you mention this cycles,
line 370 temperature of the melting zone.
In line 383 you explain the difference with the experiment and the numerical model, did you perform the experimental setup? In the conclusions is also mentioned. This experimental information has to be available in one section of the experimental work. Also include some photographs of the real result vs the simulation one would be nice. Please explain this lack of data and fix it in the paper.
Author Response
Comments of reviewer 1
- The research paper is interesting and has a good point of view, however, there are several issues before being ready for publishing.
Response : Thank you very much for these valuable comments. All comments are taken in consideration.
- The introduction is lack of references, there are several paragraphs afirming things that they are not addecuately cited, please add the references of this affirmations. Specially in the firsts paragraphs. One example where you can find information is: https://doi.org/10.1007/s40684-020-00302-7 or https://doi.org/10.1007/s40684-020-00302-7 among others.
Response : The same response of reviewer 2 (comment 1). The introduction was improved and at least 5 references are added. The novel section was highlighted (yellow) in paper.
- Please, explain the geometry description, the numbers selected for the layers are obtained from experiments? THe height is remarcably precise with 4 significant digits, please explain.
Response : That’s wright, 4 digit is reasonable in numerical approach element mesh dimension (equivalent to each layer). The four digit value (0.9071 mm) is the thickness of each layer and its obtained from the height of the part to fabricate (38.1 mm) divided by the number of layers (42) : 38.1 / 42 =0.9071 mm (totally superposed on numerical mesh nodes coordinates). The geometry description was reported in figure 3 and figure 4. The novel detailed figures are the following :
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Figure 3 |
Figure 4 |
- Figure 5 and the method for printing layers is not clear, it generates the clad tracks alternative? Only go to the right? The figure and the explanation is confusing.
Response : The figure 5 was modified to be more clear and its devided in a- and b- for n and n+1. This paragraph and these figures are inserted in the manuscript : “During the processing of the nth layer, the laser travels from left to right, following the order shown in Figure 5(a). For the subsequent return pass (layer n+1), the laser follows the same order as the previous pass, but in the reverse direction, starting from right to left (Figure 5(b)).”
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(a) Layer n |
(b) Layer n+1 |
- You detail the thermal properties until 870º, but the mateiral using DED is melted, so the original temperature should be from at least this temperature, around 1500ºC, did you consider this fact?
Response : That’s wright. The table 4 shows only an example of thermal properties dependency in the range of [20-870 ºC]. Interpolation till 1500 ºC (and more) was automatically applied in the used Abaqus software. Starting from 20 ºC is useful especially during cooling, subsequent cooling phase and solidification process.
- Line 339, it is called molten pool, not pool of melt. Also, the heat source do not only fuses the powder but also the substrate, or previous layers, you can have here a text where in the introduction this part is well explained: https://www.mdpi.com/2075-4701/10/10/1291
Response : The modification was done.
- In model validation you mention different printing strategies, but it is not clear in the materials and methods. Please explain in the constitutive model what strategies will be performed.
Response : This section was added in section 2 Constitutive model :
“In this study, the effects of scan mode, preheating, and the Zig-Zag strategy on the mechanical and thermal response during printing are investigated. The most suitable strategies will be recommended to decrease the manufactured part's distortion and residual stress. Scan mode refers to the variation of the laser's travel pattern and power during powder fusion. Different scan modes, such as unidirectional, bidirectional, alternating, laser power variation can significantly impact heat distribution and material microstructure. Preheating involves heating the build bed before printing to reduce temperature gradients during fusion, improve layer bonding, and minimize deformations. The Zig-Zag strategy deposits powder in a raster pattern to distribute heat and residual stresses more evenly, enhancing the dimensional stability of the printed part. Thermomechanical finite element DED simulations are conducted to evaluate these strategies and compared with printing experiments [36]. The distortion and residual stresses of the printed parts are compared, and the strategy that minimizes these defects is identified. Based on the findings, the most suitable DED printing strategies for fabricating high-quality metal parts are recommended. Guidelines for selecting the optimal strategy based on the geometric features and desired properties of the part are also provided.”
- What is the time of each layer? In the graphs you mention this cycles, line 370 temperature of the melting zone.
Response : The pseudo time of DED simulation is up to 50 minutes for a total of 42 layers. This time exclude inter-layer dwell times that can be studied in future paper similarly to [36]
- In line 383 you explain the difference with the experiment and the numerical model, did you perform the experimental setup? In the conclusions is also mentioned. This experimental information has to be available in one section of the experimental work.
Response : We didn’t performed any experimental setup. The numerical results are compared with previous experimental measurements reported in [33] in order to guarantee simulation accuracy.
- Also include some photographs of the real result vs the simulation one would be nice. Please explain this lack of data and fix it in the paper.
Response : All real result (photos, sensors, ..) are reported in reference [33]. In section 4. Results and discussion (line 334), authors mention : “In addition, the numerical results are compared to experimental measurements reported in [33] to ensure AM simulation accuracy.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn this paper, the introduction part need to be improved on current research status, such as who else has done the relevant numerical simulation analysis to predict the DED distortion, and what is the novel aspect in this paper.
Several figures need revision to improve the overall quality. Add dimension numbers in Figure 3 and Figure 4. The flowchart of Figure 6 should be redrawn. Avoid wavy red underlines in images, such as in Figure 9.
Where do authors obtain the list of thermal dependency properties of INCONEL 625 in Table 4, by any calculation or from any reference?
In Figure 7, the caption "Material activation" needs more details and the texts need to describe how material activation actually works.
I would suggest to use SI units (such as kg instead of tonne) in the paper, like Table 5.
Consider using another way to draw the laser paths in Figure 5 and Figure 15 to be more understandable.
Comments on the Quality of English Language
There are a few typos in the manuscripts which should be doublechecked and corrected.
Author Response
Comments of reviewer 2
- In this paper, the introduction part need to be improved on current research status, such as who else has done the relevant numerical simulation analysis to predict the DED distortion, and what is the novel aspect in this paper.
Response : The introduction was improved according to your valuable comment. This section was added/improved with at least 5 novel references. The novelty in our paper is related to implementing laser scan strategies (especially Zig-Zag) and the variation of laser power. At each strategy, the serial events and activation event sequence are generated due to the flexible and robust numerical DED model.
Her is the added section in the introduction :
“Numerical simulation analysis using the finite element method (FEM) is a valuable tool for predicting DED distortion and residual stress [12]. For instance, Ninpetch et al. [13] developed a 3D FEM model to predict these factors in a titanium tibial tray fabricated using Laser Powder Bed Fusion (LPBF), a related AM technology. Their findings highlighted the significant influence of heat source power and layer thickness on distortion near the interface between the tray and support structure, due to differing stiffness between the solid part and support. This emphasizes the importance of FEM analysis in understanding the impact of process parameters on DED outcomes. In addition, the FE models and experimental tests can be used to study the effect of various process conditions to find the optimal set of operational parameters [14]. Corbin et al. [15] used a DED experimental setup of Ti–6Al–4V and study the effect of substrate thickness and preheating temperature on distortion. Daniel et al [16] devel-oped predictive models of the actual deposition height of the part manufactured by the DED to improve the understanding of the process and calculate the expected proper-ties of the parts before the actual manufacturing. Based on the developed artificial neural networks (ANN), geometric deviations could be anticipated by adapting the la-ser power, scanning speed and powder feed. But generating these models is often time consuming. In this paper, numerical simulations and novel analytical reliability analyses are implemented to detect and predict the distortions of a part obtained by the DED pro-cess. The modeling and simulation are performed using Abaqus software [17] coupled with input files representing geometries, serial events, scan strategies and physical properties of material and laser. The developed numerical approach let possible to conduct coupled thermomechanical simulations, including the proper use of progres-sive activation of elements, several printing strategies such as laser scan modes, pre-heating and laser power.”
The Abstract was also modified to clarify the novelty in this paper.
- Several figures need revision to improve the overall quality. Add dimension numbers in Figure 3 and Figure 4. The flowchart of Figure 6 should be redrawn. Avoid wavy red underlines in images, such as in Figure 9.
Response : Dimension was added in Figures 3 et 4 :
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Figure 3 |
Figure 4 |
The flowchart of figure 6 was redrawn as requested:
Wavy red underlines were removed from images, such as in Figure 9.
- Where do authors obtain the list of thermal dependency properties of INCONEL 625 in Table 4, by any calculation or from any reference?
Response : The list was obtained from reference [36]
- In Figure 7, the caption "Material activation" needs more details and the texts need to describe how material activation actually works.
Response : Thise section was added to more explain the activation process :
“Figure 7 shows the material activation sequence (MAS) (input file Abaqus), which defines the order of material deposition, is cross-referenced with the finite element mesh activation sequence. The MAS dictates when elements transition from a non-material state to a material state. Otherwise, the mesh activation sequence governs which elements participate in calculations for a specific step. This activation ensure that elements become active only when the corresponding material is deposited.”
- I would suggest to use SI units (such as kg instead of tonne) in the paper, like Table 5.
Response : its so long and complex to change in the toalt simulation codes (abaqus input files) this SI units. One simulation takes mores than 60 hours. Sorry for this.
- Consider using another way to draw the laser paths in Figure 5 and Figure 15 to be more understandable.
Response : its done.
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Figure 15 |
Figure 5
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAll issues solved
