*2.1. Response Surface Method*

In the AM, the response surface methodology (RSM) is a superb opportunity for recognizing a connection between the input and output parameters. In this study, based on three input parameters (layer thickness, infill percentage, extruder temperature) and three output parameters (maximum failure load, thickness, and build time of parts), an experimental investigation was carried out to create some 3D samples by using the RSM with least structure defects. Also, the statistical analysis was carried out on experimental data using the Design-Expert V8 software. The statistical analysis was designed based on the central composite design (CCD) full replication with three factors on five levels. Table 1 illustrates the levels of controlled factors. The designed experiments and results of tests are shown in Table 2.


**Table 1.** Levels of independent variables.


**Table 2.** Design matrix and experiments results.
