Elastic Registration for Non-Destructive Testing of Additively Manufactured TPMS Lattice Structures

In additive manufacturing, defects lead to deviations between the as-designed versus the as-manufactured product. This challenge is pronounced for intricate lattice structures such as triply periodic minimal surface (TPMS) lattices; where hidden features complicate the quality assurance procedure. Micro computed tomography based on x-rays is the best method for the non-destructive testing of such lattice structures. However, this method is costly and time-consuming. Here, we propose a framework to accelerate the non-destructive testing of such lattices by reducing the time needed from a few hours for scanning to approximately 100-200 seconds. We propose an elastic registration framework that will use a few computed tomography (CT) projections to deform the prior available computer aided design (CAD) model such that an as-manufactured mesh is obtained. This mesh can then be used for quality control and deviation analysis. In addition, our work proposes the use of surface determination method to reconstruct the mesh for validation, geometry x-ray simulator to reduce the time and cost, and a learning-based approach for elastic registration. To demonstrate our algorithm, we conduct a case study on using TPMS lattice structures for bone-replacement applications such as scaffolds and implants. We compare three different gyroid-based geometries (i.e. sheet-based, strut-based, and hybrid) with trabecular bone structure. We also demonstrate that a hybrid lattice structure made of a combination of sheets and struts presents better manufacturability and is more suitable to construct scaffolds for bone replacement applications. The proposed framework contributes to industry 5.0 where accelerated and accurate quality assurance aid human-centric decisions.