Three-dimensional (3D) printing has emerged as a new promising technique for the production of personalized dosage forms and medical devices. Polyvinyl alcohol is prominently used as a source material to produce 3D-printed medicines via fused deposition modeling (FDM)—a technology that combines hot melt extrusion and 3D printing. A preliminary screening of three grades of PVA indicated that partially hydrolyzed PVA with a molecular weight (MW) of 31,000–50,000 and plasticized with sorbitol was most suitable for 3D printing. Paracetamol was used as a model drug. The materials and the produced filaments were characterized by X-ray powder diffraction (XRPD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The complex viscosity (η*) of the polymer melts was determined as a function of the angular frequency (ω) at the printing temperature to assess their printability. Three-dimensional printlets with a 40% infill exhibited an immediate release of the API, while tablets with a higher infill were prone to a prolonged release regardless of the filament drug loading. A factorial design was used to give more insight into the influence of the drug-loading of the filaments and the tablet infill as independent variables on the production of 3D printlets. The Pareto chart confirmed that the infill had a statistically significant effect on the dissolution rate after 45 min, which was chosen as the response variable.

Background/Objectives: Oscillatory rheology is widely used in hot-melt extrusion (HME) and fused deposition modeling (FDM), but its translation into compact formulation-screening criteria remains limited. This study re-analyzed an existing PVA–sorbitol–paracetamol dataset to derive rheology-informed working thresholds for HME/FDM processability. Methods: Temperature-ramp oscillatory rheology was used to extract formulation-level descriptors: process-temperature complex viscosity (|η*|) at 185 and 200 °C, Processing Window Fraction (PWF) within the 0.8–10 kPa·s corridor, and crossover-related temperature information. These descriptors were interpreted against empirical extrusion at 200 °C and printing at 185 °C. Results: S1.25 and S1.5 showed rheological behavior compatible with successful extrusion, whereas S1.75 showed pronounced softening consistent with over-plasticization and process failure. Paracetamol further reduced complex viscosity while maintaining processability in P5–P15. The lowest successful process-temperature viscosity values, observed for P15, supported working thresholds of approximately 0.460 kPa·s at 200 °C and 0.899 kPa·s at 185 °C. PWF complemented thresholding by describing the practical temperature flexibility of each formulation. Conclusions: Process-temperature |η*|, PWF, and crossover-informed interpretation provided a compact, formulation-specific screening framework for this PVA-based HME/FDM model system. The proposed thresholds are operational derivation outputs and require prospective external confirmation.