Toward the understanding of temperature effect on bonding strength, dimensions and geometry of 3D-printed parts

Fused filament fabrication (FFF), which is an additive manufacturing technique, opens alternative possibilities for complex geometries fabrication. However, its use in functional products is limited due to anisotropic strength issues. Indeed, the strength of FFF fabricated parts across successive layers in the build direction (Z direction) can be significantly lower than the strength in X–Y directions. This strength weakness has been attributed to poor bonding between printed layers. This bonding depends on the temperature of the current layer being deposited—at melting temperature (T_m)—and the temperature of the previously deposited layer. It is assumed that depositing a layer at T_m on a layer at temperature around crystallization temperature (T_c) would enable higher material crystallinity and thus better bonding between previous and present layers. On the contrary, if the previous layer temperature is below T_c, material crystallinity will be low and bonding strength weak. This paper aims at studying the significant effect of temperature difference (ΔT) between previous and current deposited layers temperatures on (1) inter-layers bonding strength improvement and (2) part dimensions, geometry and structure stability. A 23% increase in the inter-layers bonding strength for previous layer temperature slightly higher than T_c reported here confirms the above assumption and offers a first solution toward the increase in inter-layers bonding strength in FFF.