High-quality support-free printing of overhanging structures based on continuous layer-height variation within the same layer in FDM

3D printing technology has demonstrated tremendous potential in the field of manufacturing. Complex structural components with overhanging features in the FDM printing process typically require support structures to assist in forming, which affects printing efficiency and surface accuracy. Support-free 3D printing technology enables the fabrication of overhanging structures without the need for supports. However, existing support-free printing methods often rely on multi-axis equipment such as expensive robotic arms, and the stair-step effect occurs during the generation of self-supported inclined surfaces, leading to a significant reduction in strength in the overhanging regions. To address this issue, this paper proposes a low-cost, high-quality method for support-free printing of overhanging structures. The proposed approach is based on conventional 3-axis printing equipment and adopts a layer-height continuous variation strategy within the same layer to generate self-supporting inclined surfaces. The results show that the method not only enables low-cost support-free printing of overhanging components but also enhances the strength of connecting regions, which improves the overall mechanical performance of the printed part. To substantiate the efficacy of the proposed methodology, an experimental evaluation was performed using polylactic acid (PLA) as a representative material. The results indicate that the method achieved a 64.5% correction rate for the step effect, improved the average structural strength by 20%, and significantly enhanced surface quality with a printing temperature of 210°C, an ambient temperature of 40°C, a layer height of 0.1 mm, and a printing speed of 60 mm/s.