Z-Stitching Technique for Improved Mechanical Performance in Fused Filament Fabrication

Fused filament fabrication (FFF) is a widely used additive manufacturing technique that enables the rapid, layer-by-layer creation of parts. However, its traditional planar deposition approach can produce strong material anisotropy in terms of moduli and strengths, especially when fiber-reinforced polymers are processed. These characteristics limit the application of FFF in high-performance fields. This study introduces a novel FFF printing technique, termed z-stitching, which incorporates interlocking stitch patterns to enhance interlayer interaction and reduce anisotropy. A z-stitching algorithm was developed to explain the toolpath and material deposition. Using polymer filaments, samples employing the z-stitching technique were produced as a proof of concept. Moreover, experiments were conducted to explore the mechanical properties of samples made using z-stitching. Test results in terms of moduli and strengths in different principal material directions, as well as an isotropy ratio, were contrasted with the mechanical properties of samples made using traditional FFF. The experiments showed an overall enhanced mechanical performance of parts made using z-stitching. A printing time analysis was also performed, revealing that z-stitching printing time is approximately 14% longer than that of the comparable traditional FFF processes. This study establishes a foundation for the further optimization of z-stitching and its adoption in industrial-scale additive manufacturing for structures in high-performance applications.