Tunable digital material properties for 3D voxel printers

Purpose - Digital materials are composed of many discrete voxels placed in a massively parallel layer deposition process, as opposed to continuous (analog) deposition techniques. The purpose of this paper is to explore the wide range of material properties attainable using a voxel-based freeform fabrication process, and demonstrate in simulation the versatility of fabricating with multiple materials in this manner. Design/methodology/approach - A representative interlocking voxel geometry was selected, and a nonlinear physics simulator was implemented to perform virtual tensile tests on blocks of assembled voxels of varying materials. Surface contact between tiles, plastic deformation of the individual voxels, and varying manufacturing precision were all modeled. Findings - By varying the precision, geometry, and material of the individual voxels, continuous control over the density, elastic modulus, coefficient of thermal expansion, ductility, and failure mode of the material is obtained. Also, the effects of several hierarchical voxel microstructures are demonstrated, resulting in interesting properties such as negative Poisson's ratio. Research limitations/implications - This analysis is a case study of a specific voxel geometry, which is representative of 2.5D interlocking shapes but not necessarily all types of interlocking voxels. Practical implications - The results imply that digital materials can exhibit widely varying and tunable properties in a single desktop fabrication process. Originality/value - The paper explores the vast potential of tunable materials, especially using the concept of voxel microstructure, applicable primarily to 3D voxel printers but also to other multi-material freeform fabrication processes.