On the Registration of Thermographic In Situ Monitoring Data and Computed Tomography Reference Data in the Scope of Defect Prediction in Laser Powder Bed Fusion

Round 1

Reviewer 1 Report

1. Process monitoring and sensing are widely used across many industries for quality assurance and to increase machine uptime and reliability.

  2. Though still in the emergent stages, process monitoring is beginning to see strong adoption in the additive manufacturing community through the use of process sensors recording a wide range of optical, acoustic, and thermal signals.

3. Laser powder bed fusion is normally used for defect prediction, but in this manuscript, it represents an adaptive volume adjustment algorithm that is based on the porosity distribution in the specimen. which is able to detect porosity location and irregularity prediction by three-dimensional image-to-image registration. 

4. Also, a novel shape adjustment method was introduced to eliminate the surface deformation history that was found in the manuscript. 

5. Why is Laser Powder Bed Fusion (L-PBF) better than other existing techniques? Authors should present a comparative table that can be more attractive to readers.  

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Additive Manufacturing techniques are increasingly being adopted for the production of complex geometry parts in order to reduce cost and weight. However, some defects like pores, are inherent to the process and could be a limiting factor. From a Thermodynamics point of view, the formation of pores in AM processes (which have a severe heating source) is a result of the increase in entropy and the decrease in Gibbs free energy, being a spontaneous phenomenon.  Nevertheless, attempts of defect prediction, such as the scope of the proposed paper, are an important research theme since the scanning process parameters could be simulated and optimized before the production of the real part, thus reducing loss. The paper gives a detailed description of an Image Registration process that correlates thermographic data obtained during the production of a specially designed specimen with X-ray Micro Computed Tomography data referred to the observed pores after the production of the same specimen. A proper literature review is given in the Introduction chapter. The experimental techniques for the necessary data acquisition and processing are also described in detail, but more data regarding the material used in the experiments could be presented, seeing that the only information in paper is “… using AISI 316L stainless steel powder” (line 157). More powder data, like particle size distribution, may be important for the potential readers of the paper. As for the methodology, a variety of algorithms, adjustment functions and a compression factor were cited in the data processing strategies. Given the meticulous work carried out, the conclusions seem modest and a little disappointing, but are in accordance to the results. This reviewer suggests only a few amendments so that the article can be published.

1) Line 71 (page 2): “even” instead of “already”.

2) Line 98 (page 2): define “IR” (infrared).

3) Line 102 (page 3): define “LoF” (lack of fusion).

4) Line 163 (page 4): I suggest “performed” instead of “realized”.

5) Line 233 (page 5): Table 3 (instead of Table 2).

6) Line 314 (page 9): “assumed that” instead of “assumed, that”.

7) Line 358 (page 10): could you define or explain the ISO50% value?

8) Line 392 (page 11): consider using “topography” instead of “topology” (also in line 688).

9) Lines 394-7 (page 11): please comment the low number of pores in the transition zones 1 to 2 and 3 to 4. Was this an expected result?

10) Lines 472-8 (page 14): is it possible to specify a criterion for the starting and stopping points of pore transition?

11) Line 640 (page 19): the word “that” is written twice.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf