Accuracy in Additively Manufactured Impeller Patterns: An Experimental Study of Dimensional Fidelity and Surface Integrity

Impellers are critical components in industrial applications, requiring smooth surfaces and precise dimensions. Traditional investment casting methods are often time-consuming and costly. Fused filament fabrication (FFF), an additive manufacturing (AM) technology, offers a faster, more cost-effective alternative. FFF produces 3D-printed sacrificial patterns directly from a CAD file, making it ideal for low-volume and complex patterns. Unlike wax patterns, which can shrink or distort, 3D-printed patterns offer precise tolerances and allow for thin-walled geometries. FFF also eliminates the need for tooling, reducing capital investment. However, achieving the desired surface finish and accuracy remains a challenge. In this study, a semi-open, single-shrouded centrifugal pump impeller was fabricated using FFF with acrylonitrile butadiene styrene (ABS). A Taguchi L9 (33) design of experiments was employed to investigate the influence of layer thickness (0.08–0.24 mm), extrusion temperature (260–280 °C), and infill density (30–70%) on dimensional accuracy and surface roughness. Dimensional deviations were evaluated for critical features, including outer diameter (OD), inner diameter (ID), blade thickness (BT), shroud thickness (ST), and blade height (BH). Results show that small and thin features (BT, ST, BH) exhibited deviations with standard deviations below 0.08 mm, whereas OD was the most affected feature with a maximum standard deviation of 0.362 mm due to dominant shrinkage effects. The optimal parameter combination for minimum dimensional deviation was identified as 0.08 mm layer thickness, 280 °C extrusion temperature, and 70% infill density. Surface roughness analysis revealed that layer thickness was the most significant factor, with Ra values ranging from 4 to 7 µm, which falls within acceptable limits for investment casting. Surfaces parallel to the XY plane demonstrated superior surface quality compared with XZ/YZ planes, highlighting the feasibility of FFF-printed ABS patterns for investment casting of complex impellers.