Predicting the surface contact angle based on real-time temperature and pressure sintering principles in the fused deposition modeling process

• The SCART method is proposed to map the fuse temperature to the surface contact angle of FDM printed parts. • The model incorporating pressure into sintering theory can improve bond length prediction and surface structure accuracy. • The structural angle variable refines the wetting equilibrium equation for the surfaces of FDM prints. Fused deposition modeling (FDM) technology presents significant opportunities for the low-cost production of complex three-dimensional structures. The issues of surface roughness and step effects caused by the layered structures formed during the FDM process have been extensively studied. However, this layered structure also plays a crucial role in the formation and stabilization of air pockets during the surface wetting process of FDM prints. Nonetheless, related studies remain relatively limited. To delve deeper into the surface wettability of FDM prints, we propose the surface contact angle prediction method (SCART, Surface contact angle prediction based on the real-time temperature) in this paper for predicting the contact angle based on the real-time temperature and pressure sintering principles in the fused deposition modeling process. By incorporating the role of pressure into the traditional FDM sintering theory, the surface structure of the printed part is modeled. Based on the dimensional characteristics of the surface structure model, a wetting equilibrium equation was established with the structural angle as a variable, enabling the evaluation of the surface wettability of the printed part and the prediction of the contact angle. The method was validated by FDM fabrication of 15 % carbon fibre-reinforced polylactic acid (15 % CF-PLA) prints, and the results show that changes in printing parameters affect pressure and sintering behavior to varying degrees, thereby altering the overall structure and bond length. The SCART method has an average relative error of 3.33 % in prediction, and the maximum error is controlled to be within 9.8 %. This provides an effective method for predicting the surface contact angle of FDM prints.