[The cushion ability of lining materials for the setting and heating expansion of plaster bonded investment in casting ring. Part I: For casting mold cavity of inlay type (author's transl)].

Abstract

We measured the dimensional change of mold cavity in casting ring and casting accuracy for inlay type casting using two kinds of lining materials in various conditions. These lining materials were asbestos ribbon and ceramic fiber. In the comparison of cushion ability for the expansion of investment in casting ring of these two lining materials, following results were obtained. 1. Compressibility of ceramic fiber was twice as much as asbestos. And, two sheets of ceramic fiber ribbons had enough ability for free expansion of investment in casting ring. 2. More than two sheets of asbestos ribbons in dry state had the ability of compensation for casting shrinkage in heating process. 3. Asbestos ribbon in wet state made a setting expansion of investment larger, but had not any ability of cushion for heating expansion of investment. 4. If the cushion ability of lining materials was not enough, the mold cavity shrank. The order of this shrinking inclination were no lining material state, two sheets, one sheet of wet asbestos, and one sheet of dry asbestos. 5. This shrinking inclination of smaller cavity was greater than that of larger cavity. That meant that the larger thickness of investment in ring made this shrinking inclination greater. 6. In case of without mold cavity, the heating expansion of the investment toward the casting ring were same value at any position in casting ring.