The Investigation of Interlaminar Failures Caused by Production Parameters in Case of Additive Manufactured Polymers

Reviewer1

Firstly, the manuscript should again go through a grammar check. 

Professional translator has checked again.

Furthermore, I still do not think "failure" is the right term to use. Porosity is a more appropriate term.

The text has been modified accordingly.

Due to the nature of this phenomenon the failures can be named as porosity, but, since this phenomenon should not appear in a perfect case it may better to name as failures.

line 60: If the exact type of material is not important, will the results be the same in the case of any PLA? There are several PLA variants that exhibit different viscosities and different MFI. The grade of the PLA or at least, the supplier should be provided. What is Bq?

The text has been modified accordingly.

To perform this study for matrix material, a commercial PLA (Polylactic acid) filament – produced by Bq, a Spanish filament supplier - has been used. For this investigation the exact type of material was not important, since in our article just the nature of this phenomenon has been investigated. Properties of different materials surely can influence of this phenomenon, but its nature will be the same.  PLA is a thermoplastic, holocrystal-line polymer produced by polycondensation or fermentation of hydroxy propionic acid. It behaves as a rigid material at room temperature, with the tensile strength of 50 MPa, and breaking strain of 3-5% - according to the manufacturer [34].

In this paper three printing parameters were investigated. Layer height and printing speed have a great affect on surface quality and costs. The smaller the layer height is, the longer the manufacturing is. Furthermore, they may have effect on mechanical properties. Temperature is a serious point during polymer manufacturing. Some important proper-ties of polymers like Melt Flow Index (MFI), decomposition depends on temperature, which means optimum must also be known for high quality 3D printing.

Line 63: Again, it is just one of the values for a PLA. cannot generalize the properties. try to mention the range

This is the official data of the manufacturer.

Line 73: optimum printing parameters should be identified.

It can be optimized for several purposes. We determined how changes in layer thickness, as well as print speed, affect stiffness. In the range of operation, there is not an exact optimum value. The increasing the layer thickness and printing speed increases the extent of the porosity.   In the case of the printing temperature we determined the optimal value.  

Line 90: if--> in

The text has been modified accordingly.

Table 1: the sample numbering is not uniform

The table has been modified accordingly.

Figures 7,8,9,10,12,14 are difficult to read. The font size and line thickness should be increased.

Figures are modified accordingly. The font size and line thickness significantly increased in case of Figures 7,8,9,10,12,14. With zoom the figures are sharp and clean to be read.

Line 130: degressively increasing? degressive: tending to descend or decrease[Merriam-webster]
The wording should be changed. Same in line 185

The text has been modified accordingly.

Furthermore, the three lines are actually not necessary, are they? They are just the standard deviations for the mean value?

The three lines are necessary, the minimum and the maximum values are describing the sample, and very rarely have connection with deviation. In statistics the deviation is a measure of average difference between the observed value and the aritmetic mean. Therefore, the deviation is much smaller then the difference between maximum and minimum.

Can authors present a 3D surface plot that would facilitate an easier understanding of the parameters influencing the tensile strengths?

Very good idea, authors also thought about it. However, authors would like to kindly remind the reviewers about the models of which have more then 3 dimensions are very hard to visualise. In our case 3 input and 1 output parameters were definied, therefore our 4 dimensional model could be presented in 3 pieces of 3D diagrams (3D surfaces) or 6 pieces of 2D graphs. For better understanding authors have chosen to make the 2D graphs. Authors have only showed the connection between input parameters and output parameter, so only 3 pieces of 2D graphs were incorported:

• tensile strength - layer thickness

• tensile strength - printing speed

• tensile strength - printing temperature

An additional difficulty is that the scaling of different physical quantities on different axes greatly influences the nature of the surface.

As a conclusion authors kindly as the reviewers to accept the 2D graphs.

Instead of using other author's images, why can't authors use their own images if they too observed similar defects during printing?

Where we had our own figure we used it. All other source were indicated.

Furthermore, for figure 13, reference 44 is wrongly cited.

The text has been modified accordingly.

Equation 2 what is F and A?  Force at the break? and what are the values of A? was A constant for all the cases?

F is Force at the break (calculated). A the real cross section (Theoretical cross section minus the air gaps (porosity) in the investigated cross section). These values ​​vary depending on the investigated printing parameters.

Line 132: Just one statement was provided. Why are the failure lengths decreasing and increasing? what are the factors influencing them? aren't figures 9 and 14 contradicting each other? Figure14 shows an increase in properties however increase in failure length?

There is no contradiction between figures 9 and 14. In both figures, it can be seen the same optimal value of the printing temperature.

Figure 14 shows an increasing properies up to the optimum point. Figure 9 shows a decreasing failure length up to the optimal point. 

also, there are only 3 curves on the left side and 5 representative points on the right-side figure. How is it possible? can authors present all the curves?

The detailed explanation can be found in the text just below Figure 10. 

Figure 12: If standard, increased and decreased refer to layer thickness, why are they again presented here? Why are the curves same in the figure 10 and 12?

Figure 12 has been corrected. Unfortunately in the editing process we copied the wrong diagram on the left side of the figure.

Line 165: two thickness values were mentioned and which is the actual thickness. And what is the part thickness? 

The text has been modified accordingly.

Comments on the replies:

1. Even if the tests from the other paper are taken in this study, still the standard deviations and the mean values of those tests should be provided to get an idea.
2. The experimental part should at least be explained in this paper. Furthermore, the authors stated that the validation should be carried out on standard specimens (Line 163). If the standard specimens are no used in this study, can the results be the same in every case?

1. In the cited literature, unfortunately, only the average values appear with different printing parameters. The deviations or other statistical parameters were not available.

2. The text has been modified accordingly.

Still, the conclusions are not clear and concrete.

The text has been modified accordingly.