Parameter Optimisation in Selective Laser Melting on C300 Steel
Round 1
Reviewer 1 Report
The paper is devoted to the study of the parameters’ optimization of the SLM process for the production of the parts made of C300 steel. The authors provide mathematical model, nomograms and response surfaces to optimize some of the key parameters in the SLM printing process, such as laser power, laser speed and hatch spacing. Based on the proposed model, printing parameters are calculated in terms of obtaining the best mechanical properties, such as yield strength, tensile strength and relative elongation.
This approach of predicting is well know as authors stated in the introduction. However, there is no much research content. The model cannot be presented as a completed research without sufficient experimental background, such as optical microscopy, SEM, XRD, microhardness, etc.
The tensile test results are insufficient for a reliable conclusion. In addition, the model adequacy calculation should be provided separately.
The reviewer suggests the authors extensive revision of the paper.
The following remarks and comments are advised to be reviewed in the text.
- Page 2, Table 1. Steel composition is given incompletely, at least Si, Cr, Mn are missing.
- Page 2, Table 1. The composition percentage is not specified, wt. or at.?
- Page 6, Figure 2. No bars in pictures with fractured surface for specimens 1 and 15. The latter two bars in pictures for specimens 7 and 8 are too small.
- Page 6, Figure 2. Optical microscopy is not mentioned in the methodology. Provided pictures are not informative, magnification is too low. In order to show the type of fractured surface (brittle or viscous) SEM is usually used.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Line 86-89: Add requirements for parameter (A).
Line 156: What was the justification for producing only one batch of samples for the tensile test ? Testing a larger number of samples could completely change the test results and significantly affect the proposed optimal SLM parameters. It cannot be ruled out that with a larger number of samples made with the same parameters SML, a fluctuation of the tensile test results could occur. During standard tensile test, it is min. two samples, and during experimental work, it is worth planning even more trials in case of large dispersion of results. For example, the authors K.Kempen et al. „Microstructure and mechanical properties of Selective Laser Melted 18Ni-300 steel”, 2011 performed tensile tests with four SLM specimens.
Line 157: Please add larger sample diameter and length of 4 mm part or add sample drawing with all dimensions.
Line 161-162: Add an explanatory description that the tensile test specimens are in SLM condition or that a finishing treatment has been applied (e.g. fine grinding, polishing). The surface condition of the samples may affect the results.
Line 251-253: The conclusion is unfounded. There is no hard evidence for the effectiveness of the applied research approach, as samples were not made with the optimal parameters SLM and the results of their tensile tests were not presented.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
The article is interesting, well written and very useful. On the other hand, the experiment plan can be selected different, more accurate, more precisely reflecting the influence of input parameters on the effect of laser processing - additive technology (but this is a proposal for further research).
Comments and suggestions for further research
In the above experiment, three levels of variability of the independent variables were adopted, namely:
P [W]: 1, 0, -1 in the studied area of ​​parameter variability [250W -200W], that is: 250, 225, 200 [W];
S [mm / s]: 1, 0, -1 in the examined area of ​​parameter variability [800 mm / s -500 mm / s], that is 800, 650, 500 [mm / s];
H [mm]: 1.0, -1 in the studied area of ​​parameter variability [0.14 mm -0.08 mm], that is 0.14, 0.11, 0.08 [mm;
In this case, assuming three levels of variation for each independent variable, when analyzing the effect of "independent variables" on the "investigated dependent variable", we obtain a function based on three points, which is less accurate than when using a rototable design of the experiment at five levels of variation for three independent variables.
In subsequent studies, I propose to use the "rototable design of the experiment at five levels of variation" with three independent variables, namely:
The function for describing the results is also a second order polynomial with interactions;
15th experiment - in the "center of the plan" should be repeated 3-5 times and the average result should be given;
+1.682, -1.682 - "star arm" for the three independent variables in this plan.
The costs associated with running the experiment on five levels of variability of the independent variables are not greater than in the case of the experiment plan used in the article, but they provide a more detailed description of the function of the second degree polynomial with interactions.
Levels of variation for the three independent variables in coded form:
1. + 1
2. -1
3. +1.682
4. -1.682
5. 0
Experiment matrix in coded form:
|
Nr experience |
P[W] X1 |
S [mm] X2 |
H [mm] X3 |
|
1 |
-1 |
-1 |
-1 |
|
2 |
+1 |
-1 |
-1 |
|
3 |
-1 |
+1 |
-1 |
|
4 |
+1 |
+1 |
-1 |
|
5 |
-1 |
-1 |
+1 |
|
6 |
+1 |
-1 |
+1 |
|
7 |
-1 |
+1 |
+1 |
|
8 |
+1 |
+1 |
+1 |
|
9 |
-1,682 |
0 |
0 |
|
10 |
+1,682 |
0 |
0 |
|
11 |
0 |
-1,682 |
0 |
|
12 |
0 |
+1,682 |
0 |
|
13 |
0 |
0 |
-1,682 |
|
14 15 |
0 0 |
0 0 |
+1,682 0 |
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The reviewer insists providing additional tests and analyses (optical, SEM microscopy, microhardness), no reliable conclusions can be made based on one tensile test.
Author Response
"Please see the attachment."
Author Response File: Author Response.pdf
Reviewer 2 Report
Line 156: The Authors’ justification for making only one series of sample is unsatisfactory. For each point of the experimental matrix at least 2 tensile samples had to be made, therefore 2x14=28 ! This remark needs better justification.
Line 251-253: The conclusion must be reworked to clearly show that the article is largely theoretical and indicates the possibility to use this experimental plan to the SML process research, but the research results have not been confirmed by experiment. It is worth remembering that similar experimental matrix and an approach to the analysis of the results have been used in scientific research for many years (e.g. during the development of welding consumables: covered electrodes and SAW fluxes), so some conclusions are not new.
Author Response
"Please see the attachment."
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
The reveiwer suggest to change the title of the paper. Optimized parameters are correct for only few mechanical properties based on the tensile tests. So the title should include mechanical properties.
Reviewer 2 Report
The lack of experimental verification of the research results is a signigicant drowback of the work, but after corrections the article can be published. It would be good if the Authors took into account the comments when planing further research works.
