Improving mechanical performance in FFF through non-planar 3D printing – a systematic review

Purpose This paper systematically reviews the impact of non-planar slicing strategies on the mechanical performance of fused filament fabrication (FFF) components. While prior studies have explored geometric and surface quality improvements, a consolidated understanding of mechanical performance enhancement remains limited. This review aims to quantify these improvements and identify the governing factors influencing performance outcomes. Design/methodology/approach A systematic literature review was conducted following PRISMA guidelines, analysing 24 peer-reviewed studies published between 2012 and 2025. A total of 794 samples and 233 experimental data sets were examined. A standardized “Improvement (%)” metric was adopted to enable cross-study comparison of mechanical performance, despite variations in materials, geometries and process parameters. Findings The results indicate an average mechanical performance improvement of 49.2% when using non-planar slicing compared to conventional planar approaches, although 17.2% of cases reported performance reductions. The effectiveness of non-planar slicing is strongly influenced by toolpath alignment with stress fields, high count of degrees of freedom in motion systems and usage of composite materials. Advanced implementations, including multi-axis and robotic systems, demonstrate the highest performance gains but introduce increased process complexity. Originality/value To the best of the authors’ knowledge, this is the first systematic review to aggregate and mathematically standardize the mechanical performance gains of non-planar FFF across disparate data sets. By introducing a unified comparison metric and identifying key performance drivers and limitations, this study offers both theoretical insight and practical guidance for process optimization and future research in additive manufacturing.