Abstract
The cushioning effects of casting ring liners on the setting expansion of the investment material in a split metal mould 30 mm in diameter and 40 mm in height were evaluated for the decrease in the thickness of wet ceramic liners and asbestos ribbons. The setting expansion of investment material was 0.35%, and the required decrease in thickness of liners was 0.05 mm. Decreases in the thickness of liners (δTs) were within -0.007 to 0.255 mm. With the exception of A-group (Rockwool-type) liners, δTs at the bottom side were larger than those of the upper side. (δTs tended to increase with the original thickness of the liner. In the liners with high water sorption, it was found that water absorbency and water retentiveness of the liner influences the setting and hygroscopic expansion of investment material. The correlation between δTs and cushioning effects using setting expansion measurement apparatus was significant in B-group (ceramic fiber low temperature type), C-group (ceramic fiber standard type), D-group (ceramic fiber low temperature-standard type) and AS-Group (asbestos ribbon) liners.
