Hybrid microwave sintering of centimetre-sized porcelain objects: influence of the position of the objects in the sintering cell on the densification

The combination between additive manufacturing and microwave sintering (MW) is interesting as an alternative to conventional shaping and sintering processes. The aim of this study was to sinter centimetre-sized porcelain items shaped by robocasting in a set MW device, including a set sintering cell. Identical items were sintered in different positions in the sintering cell, to mimic the sintering of different objects in a predefined device. The position of the item in the sintering cell has a strong influence on its densification. A heterogeneous densification was obtained when the item was placed in a vertical position relative to the susceptors. It was not the case when the item was placed in a horizontal position. The temperature distribution in the susceptors and the items was simulated with a simplified 2D model. The calculated temperature in the item was dependent on the size of the item and on its position relative to the susceptor. This study highlights the need to carefully adapt the sintering cell to the object to sinter.