OPTIMIZATION OF MASKING PARAMETERS FOR VOLUMETRIC MATERIAL MANUFACTURING USING INVERSE METHODS

Volumetric material manufacturing involves forming a solid shape within a precursor powder volume as a whole instead of the traditional layer by layer technique used for most additive manufacturing methodologies. This work presents an inverse technique for designing masking parameters in order to generate a predetermined shape within the precursor powder volume. The model utilizes a microwave cavity for inducing heat in BaTiO3 precursor powder via Joule heating. Material sintering and microwave propagation is modeled by coupling electromagnetics and heat conduction using finite element discretization. This interaction is complicated by the nonlinear thermal dependence of dielectric properties of BaTiO3 (i.e. density, specific heat, dielectric constant and loss tangent), which are considered here. Heat can be localized within the powder volume using one or multiple conductive masks that modulate incident energy. Utilizing both 3D and 2D models, it is demonstrated that an arbitrary nonuniform mask can create nonuniform heating in the powder volume. An experimental framework is then established to conduct a forward experiment parameterized with five masking and cavity design variables causing different powder heating patterns. Then an inverse problem is solved by specifying a desired shape and outputting a mask and cavity design capable of generating said shape. It is demonstrated that mask parameters can be optimized in order to produce a desired shape by this inverse method.