Study on vertical printing of thermally driven PLA actuators: residual stress modulation in FDM-based 4D printing

Abstract Additive manufacturing advances technologies has accelerated the development of 4D printing in the field of smart structures. While most studies on fused deposition modeling -based 4D printing focus on planar deformation control, the mechanisms governing parameter effects in vertically printed structures remain unclear. In this study, a thermally driven vertical 4D printing method was proposed. The effects of four key parameters, including nozzle temperature, line width, layer height and printing speed, on the bending angle and flattening load of PLA vertical printing sheet were systematically studied. The results indicate that nozzle temperature and A side speed have the most significant influence on residual stress regulation. When the nozzle temperature is 190 °C, the layer height is 0.26 mm, the line width is 0.25 mm, the printing speed of A side is 250 mm s −1 , and the printing speed of B side is 50 mm s −1 , the bending Angle of the sheet can reach 44.960°, and the flattening load is 7.64 N. Furthermore, a comparative analysis of residual stress development between vertical and planar printing modes revealed that vertical printing accumulates less heat and dissipates thermal energy more efficiently, resulting in substantially smaller deformations than planar-printed counterparts. Finally, a programmable, thermally responsive fan-blade structure was fabricated, integrating both planar and vertical printing strategies with gradient settings of line width and speed. This demonstration validates the feasibility of using vertical printing for achieving multi-level deformation control in complex structures. This study is the first to elucidate the dynamic interplay between anisotropic heat transfer and parameter interactions in vertical 4D printing, thereby expanding its application potential in flexible devices and intelligent actuators.