# Neuro-Fuzzy Model Evaluation for Enhanced Prediction of Mechanical Properties in AM Specimens
## 4 Methodological Framework for Enhancing ANFIS Model
### Experimental AM Data  
Based on previous work [3; 15] and literature review [4; 5; 6; 7], the printing parameters that influence the mechanical properties of the AM specimens were defined. By selecting these factors, tension, bending and torsion tests were conducted by using multiple AM technologies (FFF, SLA, SLS, DED, and PBF) and various materials (ABS, PLA, PA12, etc.) (Figure 3). All data were gathered and analyzed to obtain the stress, strain and Young's modulus of every specimen/experiment.  
Figure 3: Specimens, according to ASTM D638, for different materials (ABS and PLA (**a**)) and AM methods (FFF (**a**) and SLA (**c**)) and sample tension test (**b**).  
Figure 2: The proposed ANFIS model with 9 inputs and 1 output.  
All AM processes and materials used for this study were manufactured in the AM Laboratory and all mechanical tests were conducted at the Strength of Materials Laboratory, Mechanical Engineering Department, University of West Attica. All experiments were designed and conducted according to ASTM standards such as ASTM D638 [27], D695 [28], D7791 [29], D790 [30], and D5279 [31].  
Experiments were conducted, as shown in Figures 3 and 4, using various AM processes, including FFF, SLS, SLA, and DED. The experiments involved multiple materials, testing methods, and a range of values for selected manufacturing parameters. A generalized model for handling all 21 AM parameters as input, was created based on previous work [15]. The parameters comprised (1) AM technology, (2) testing method, (3) material, (4) infill pattern, (5) infill percentage, (6) layer thickness, (7) wall thickness, (8) speed, (9) extruder temperature, (10) laser power ratio, (11) bed temperature, (12) position on printer bed, (13) incline against printer bed, (14) twist around axis of center of gravity, (15) raster angle, (16) layers for alternating raster angle, (17) percentage of first material, (18) curing time, (19) curing power, (20) layer composition, and (21) cross-section.  
The purpose of creating a generalized model is to be able to handle any AM technology, among FFF, SLS, SLA, or DED, and its selected manufacturing parameters applicable each time, as input and output stress, strain, or Young Modulus. According to the AM technology the applicable parameters were used each time.  
For the three-point bending tests, presented in Figure 5, square section specimens were used (8 \(\times\) 8 mm). The tests were conducted according to ASTM D790. Stress-strain curves were produced by importing the applied load and deflection, from the tests, to stress \(\sigma\) (Equation (3)) and strain \(\varepsilon\) (Equation (4)) equations.  
\[\sigma=\frac{3 PL}{2 bd^{2}} \tag{3}\]  
where \(\sigma\) is the stress (N/mm\({}^{2}\)), P is the applied load (N), L is the stressed length (mm), b is the width of the specimen (mm), and d is the height of the specimen (mm).  
\[\varepsilon=\frac{6 Dd}{L^{2}} \tag{4}\]  
Figure 4: Sample bending test (**a**,**c**) and specimens (**b**), according to ASTM D790, for ABS and PLA material and FFF AM method.  
where \(\varepsilon\) is the strain (%), D is the deflection (mm), L is the stressed length (mm), and d is the height of the specimen (mm).