Optimization of the Mechanical Response in MEX Additive Manufacturing of Thermoplastic Polyimide (PI): The Impact of Key Process Control Settings

High-performance polymers have made significant progress in the field of three-dimensional (3D) printing. An increasing number of investigations have exploited these unique properties. In this context, polyimide (PI) optimization efforts for the mechanical response of 3D printed samples were performed. Such an endeavor remains unexplored thus far because of the high processing temperature required, high material cost, and complex rheological behavior. The PI filament was extruded for the 3D printing of the specimens (material extrusion, MEX). The specimens were used for mechanical and morphological examinations. The L16 Taguchi design was employed with the raster orientation, hot-end temperature (HT), printhead velocity (PV), internal fill ratio, and deposition width as generic variable control parameters. The output metrics were the ultimate yield strength, Young's modulus, and toughness (tensile test). Reduced quadratic regression (RQRM) and linear regression models were applied and compared. RQRM was found to be the most beneficial. The ranks indicated a significant influence of the PV parameter on the majority of the responses. HT was not highly ranked. High determination coefficients (<i>R</i> ² > 0.71) enabled accurate prediction of mechanical responses (confirmation run error <10%). The optimized configuration yielded an improvement higher than 250% in all three of the tensile response metrics (230% for the fourth configuration). An experimentally validated, robust framework is provided herein for the tensile response of high-performance PI thermoplastics in MEX 3D printing, thus enabling its broader utilization in aerospace, electronics, and high-temperature tooling, in which performance and reliability are critical.