Influence of Geometry and Size on Precision and Accuracy in Fused Deposition Modeling (FDM) Additive Manufacturing

This study presents a systematic evaluation of the dimensional accuracy and process capability of fused deposition modeling(FDM) additive manufacturing, with emphasis on the influence of process-induced thermal and kinematic effects on dimen-sional performance. Two geometries made of polylactic acid (PLA) were considered: a staircase specimen to assess processcapability and directional effects, and a geometric benchmark test artifact (GBTA) to evaluate dimensional reliability acrossrepresentative features. Measurements were performed using a digital caliper for the staircase model and a coordinate meas-uring machine (CMM) for the GBTA. Under manufacturer-recommended, unoptimized printing conditions, staircase analysisshowed that the investigated FDM system achieved process performance indices (P m and P mk) ≥ 1.33 at a 95% confidence level.Dimensional stability varied across the build chamber due to spatially nonuniform cooling conditions, with statistically signif-icant position-dependent deviations observed particularly along the build direction. Larger features exhibited higher relativeprecision. Achievable ISO 286-1 International Tolerance grades ranged from IT9 to IT14. GBTA results confirmed systematic un-dersizing of cylindrical and curved features. Absolute dimensional deviations remained approximately constant across nominalsizes, whereas percentage errors increased for smaller features due to scale effects. Despite these variations, the geometric formwas preserved, demonstrating high repeatability. The proposed capability-based evaluation framework provides a structuredapproach to quantifying dimensional reliability in polymer-based material extrusion processes for functional components.