Effect of warm isostatic press processing on mechanical properties of powder-based polymer additive manufacturing

Powder-based polymer additive manufacturing (AM) processes, such as binder jetting (BJT) and powder bed fusion (PBF), enable efficient fabrication of complex polymer components, but the mechanical performance of as-built parts is often limited by residual porosity. To address this limitation, warm isostatic press (WIP) processing was adopted in this study as a post-processing strategy to enhance the mechanical properties of powder-based polymer AM parts. The results show that WIP processing led to a pronounced increase in tensile strength for BJT-fabricated PMMA specimens, with strength improvements exceeding approximately 455–640%, whereas only marginal strength enhancement (approximately 3.1–5.5%) was observed for PBF-fabricated PA12 specimens. X-ray computed tomography analysis revealed that the as-built BJT specimens exhibited a highly porous structure with a relative density of approximately 61%, while the as-built PBF specimens already achieved a high relative density of approximately 93%. After WIP processing, internal porosity was substantially reduced in both cases, resulting in densities exceeding 99%. These findings indicate that the effectiveness of WIP processing in powder-based polymer AM is strongly governed by the initial porosity level and pore morphology of the fabricated parts.