The burnout process required to prepare gypsum-bonded investment casting molds was studied by collecting three different sets of data. Both wax and plastic patterns were used in these trials. The temperatures inside molds at 12 locations within mold cavities were measured as a function of elapsed time as the mold was heated in a gas-fired burnout oven. At the same time, mold weight was measured to accurately understand the various reactions, both chemical and physical, which were progressing during the burnout cycle. A material balance was used to calculate the degree of drying and wax removal as a function of time and temperature. In addition, molds were pulled out of the burnout oven at regular intervals and sectioned to observe the progress of reactions by measuring the residual carbon present in the mold adjacent to mold cavities. An effort was made to compare these results with those obtained in other trials.

Author: Dr. Shankar Aithal, Dennis Busby, John C. McCloskey