Guideline for paste extrusion 3D printing of slump-free ferrite inductor cores

Abstract

Ceramic paste extrusion 3D printing has the potential to fabricate novel designs of ferrite inductors which could lead to size reduction of power electronic devices. An important requirement of paste feedstock is the ability to retention its shape under gravity after it is printed. To reduce time and energy consumption of a 3D printing process, it is useful to know the minimum required yield stress of feedstock to retain its shape. Due to lack of reported models that link the minimum required yield stress of feedstock to the target dimension of the feedstock, we explored slumping models in concrete industry for deciding the dimension-dependent minimum yield stress of the ferrite feedstock for UV-assisted 3D printing ferrite inductors. In this study, yield stress of the feedstock was affected by UV-curing time during 3D printing. With the selected model and the characterized relationship between yield stress and UV-curing time, a guideline was developed that prescribes the shortest UV curing time per print-layer from target dimensions of a slump-free ferrite core. Feasibility of the guideline was tested on two common commercial ferrite core structures.