Study on the improvement of resin refilling at high area-to-layer-thickness ratio in DLP-type high-speed 3D printing

Purpose This study addresses the resin refilling challenge in digital light processing (DLP)-type high-speed three-dimensional (3D) printing when the cured cross-section exhibits a high area-to-layer-thickness ratio. In bottom-up systems with an inhibiting film that creates a “dead zone” at the vat bottom, raising the platform by only one layer thickness can leave the gap between the cured layer and the vat bottom incompletely refilled, causing defects. The purpose of this paper is to propose and validate process-side strategies that overcome this limitation without sacrificing printing speed. Design/methodology/approach Two complementary approaches were investigated on a custom-built bottom-up DLP-type printing platform: rotation of the printing platform during the lifting stroke, and spiral microgroove structures fabricated on the inhibiting film at the vat bottom. Four rotational modes (post-rise rotation, pre-rise rotation, simultaneous rise and rotation and rotation–rise–reverse rotation) were compared using load-cell measurements of separation force and separation time. For the selected mode, rotational speed (3–15 rpm) and rotation angle (30–120°) were swept. Microgroove structures with radial and spiral patterns were then combined with the rotational strategy and tested on cylindrical samples of 40, 50 and 60 mm diameter. Findings The “simultaneous rise and rotation” mode produced the most stable separation behavior and the shortest per-layer cycle time, while “post-rise rotation” serves as a practical alternative when the simultaneous mode is incompatible with the microgroove geometry. Rotational speed dominated over rotation angle in influencing separation force and separation time; 6–9 rpm with a 90° rotation angle was identified as the preferred operating window. Combining platform rotation with spiral microgrooves – whose orientation matches the rotational direction – raised the maximum printable area-to-layer-thickness ratio from approximately 7,000 to over 28,000, while maintaining dimensional accuracy within 2 % on bridge, edge and letter-M test features. Research limitations/implications The experiments were conducted with a single photocurable resin (polyethylene glycol (600) diacrylate + 1 wt% 2,4,6-trimethyl benzoyl diphenyl phosphine oxide, viscosity 90–100 cps at 25 °C) and cylindrical cross-sections up to 60 mm in diameter. Generalization to higher-viscosity resins, non-axisymmetric cross-sections and other inhibiting-film chemistries requires further study. Originality/value The work introduces a coupled process–hardware strategy in which platform rotation is synchronized with the lifting stroke and reinforced by spiral microgrooves whose pattern is geometrically aligned with the rotation. This coupling extends the practical printable area of bottom-up DLP-type high-speed 3D printing by roughly fourfold relative to the same system without rotation or microgrooves, providing a route toward larger-area continuous DLP printing without compromising layer time or accuracy.