3D-printed functionally-graded lattice structure with tunable removal characteristics for precision polishing

Functionally-graded lattice structure (FGLS) has fascinating properties such as lightweight, tunable stiffness, minimized stress concentration, and excellent energy absorption. The advent of 3D printing has provided feasible and reliable manufacturing solutions for FGLS, which has been boosting wider applications of FGLS. In this paper, 3D-printed polishing tools with tunable removal characteristics are developed based on FGLS. The gradient in stiffness is achieved by varying the strut thickness of different cells. Four FGLS with different gradients are designed and printed. The normal contact pressure between the tools and a rigid plate is modelled by the finite element method and experimentally validated with a pressure mapping system. The polishing performance of the developed polishing tools is investigated on both ductile and brittle materials in a machining centre. Results demonstrate that the removal profiles of the polishing tools strictly follow the change of the lattice gradient regardless of the workpiece materials, which mainly affect the depth of the polished footprints. Besides, the surface roughness Sa after polishing reaches as low as 26 nm for the optical glass, indicating a drastic improvement of more than 90%. These findings enable the fabrication of polishing tools with desired tool influence functions on-demand for form error figuring in the computer-controlled optical surface finishing. Besides, the design strategy presented in this paper will open a new realm of producing functional tools in the field of ultraprecision manufacturing.

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