Fused deposition modeling (FDM), which is a popular and widely additive manufacturing technique, opens alternative possibilities for complex geometries that are hard to manufacture using classic manufacturing techniques. Its use in functional products is however limited because of anisotropic strength issues, where the strength of FDM-fabricated parts in the build direction (Z direction) can be significantly lower than in the X-Y directions. This work aims at addressing this particular point for a not-well-known polymer, namely acrylonitrile styrene acrylate or ASA. Using central composite design and response surface methodology, the nozzle temperature (A), printing speed (B), and layer thickness (C) were studied in a systematic manner to evaluate their effects on the Z-direction tensile properties of 3D-printed ASA's samples. Analysis of variance results demonstrate that layer thickness is the most influential printing parameter on interlayers bonding. The best tensile properties for 3Dprinted ASA parts were achieved with parts produced at A = 270 C, B = 60 mm s À1 , and C = 0.155 mm. Scanning electron microscopy observation confirms that printing ASA material with those optimum parameters clearly improves the interlayers' bonding in the build direction.

Fused filament fabrication process presents drawbacks in mechanical properties observed when printing in the build direction (Z‐direction). Such anisotropic properties will affect the part's performances and have to be minimized during fabrication. This study aims to evaluate the effects of nozzle temperature, printing speed and specimen state (annealed or as‐printed) on porosity percentage and tensile properties for 3D printed polyetherimide (PEI) (ULTEM 1010) parts in Z‐direction. The results demonstrated that print speed is the most influential process parameter that should be adjusted in consideration with the other printing parameters. The specimens' state did not reveal a noticeable influence, as the amorphous nature of PEI is considered less receptive to annealing. The optimization method to achieve the best results yielded values of 360°C and 30 mm s−1 as printing conditions, followed by heat treatment. This was confirmed by porosity measurements, tensile testing, and scanning electron microscopy observations. The best performances of PEI material were 3425.5 MPa, 102 MPa, and 4.30% for Young's modulus, tensile strength, and elongation at break, respectively.