Manufacturing and Characterization of 3D Miniature Polymer Lattice Structures Using Fused Filament Fabrication.

Rafael Guerra Silva,Arístides González Zamora,María Josefina Torres,Jorge Zahr Viñuela

doi:10.3390/polym13040635

Rafael Guerra Silva, Arístides González Zamora + Show 2 more

Open Access

https://doi.org/10.3390/polym13040635

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Abstract

The potential of additive manufacturing to produce architected lattice structures is remarkable, but restrictions imposed by manufacturing processes lead to practical limits on the form and dimension of structures that can be produced. In the present work, the capabilities of fused filament fabrication (FFF) to produce miniature lattices were explored, as they represent an inexpensive option for the production of polymer custom-made lattice structures. First, fused filament fabrication design guidelines were tested to assess their validity for miniature unit cells and lattice structures. The predictions were contrasted with the results of printing tests, showing some discrepancies between expected outcomes and resulting printed structures. It was possible to print functional 3D miniature open cell polymer lattice structures without support, even when some FFF guidelines were infringed, i.e., recommended minimum strut thickness and maximum overhang angle. Hence, a broad range of lattice structures with complex topologies are possible, beyond the cubic-type cell arrangements. Nevertheless, there are hard limits in 3D printing of miniature lattice structures. Strut thickness, length and orientation were identified as critical parameters in miniature lattice structures. Printed lattices that did not fully comply with FFF guidelines were capable of bearing compressive loads, even if surface quality and accuracy issues could not be fully resolved. Nevertheless, 3D printed FFF lattice structures could represent an improvement compared to other additive manufacturing processes, as they offer good control of cell geometry, and does not require additional post-processing.

Highlights

Cellular materials have been used in different engineering applications over the years [1], additive manufacturing (AM) opens up new opportunities for their design and development
We explore the manufacturing of 3D miniature polymer lattice structures using fused filament fabrication, for lattices with cell size and strut diameter close to the smallest dimension possible
Miniature 3D open cell lattice structures could be manufactured by fused filament fabrication (FFF) without using support material, using complex unit cell geometries not limited to the classic cubic-type cell arrangements

Summary

Introduction

Cellular materials have been used in different engineering applications over the years [1], additive manufacturing (AM) opens up new opportunities for their design and development. While in conventional cellular materials cell size can only be partially controlled, AM offers control over cell size and shape, shape and size of struts, topology of the structure, and many other features [2] These features provide new opportunities for the design and fabrication of biomedical devices, such as tissue scaffolds [3,4,5,6], artificial high porosity structures with complex geometries designed to support tissue growth, for instance bone [3,7]. While analytical and numerical models of lattice structures could be used to assess their mechanical behavior, they usually do not consider local geometrical irregularities, an unavoidable consequence of the manufacturing process [14]. It does not provide information regarding the manufacturability of lattice structures via additive manufacturing. The quality of the lattice structure, including dimensional accuracy, surface quality, residual stresses, microstructure, and overall variability does influence its performance [14,15]

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