Dimensional Assessment and Measurement Uncertainty Estimation of H13 Tool Steel Specimen Fabricated using Metal Fused Filament Fabrication (M-FFF)

Abstract

This work investigates the dimensional accuracy, shrinkage behavior, and dimensional measurement uncertainty of sintered H13 tool steel specimen manufactured through Metal Fused Filament Fabrication (M-FFF), implemented in this study through a Markforged Metal X (Atomic diffusion additive manufacturing based) system. Linear, circular, and angular dimensions were characterized through a high-accuracy Coordinate Measuring Machine (CMM), and uncertainty budgets were prepared in accordance with the Law of Propagation of Uncertainty (LPU) method. Results indicate anisotropic shrinkage with the X–Y plane undergoing more shrinkage (17.0–20.0%) than the Z-direction (15.0–15.5%), due to filament packing density, layer stacking limitations, and thermal gradients during debinding and sintering. Typical uncertainty evaluation for linear dimensions of the sintered samples demonstrated the maximum combined standard uncertainty of ± 14.008 µm, whereas the expanded uncertainty computed was ± 38.8 µm (at a coverage factor k = 2.77, corresponding to the confidence level of 95% for a Gaussian distribution). Angular dimensions showed the highest deviations up to 0.23° and, maximum combined uncertainty of ± 363 Arc seconds and the expanded uncertainty of ± 1006 Arc seconds (at a coverage factor k = 2.77, corresponding to the confidence level of 95% for a Gaussian distribution). The investigation points to the significant effect of anisotropic shrinkage on dimensional deviation and underpins the need for sound uncertainty quantification to separate the true process-induced deformation from measurement randomness. For high-precision applications such as molds and cutting tools, post-processing or enhanced process control is recommended to ensure compliance with dimensional and angular tolerance requirements.