Pine Tree Castings had a chronic dewaxing problem. A high percentage of molds had to be dipped after flash firing to prevent metal runout during pouring. Special shell building and firing techniques were necessary to minimize casting defects such as excess metal, flash, bulge and residue. Eliminating mold cracking would not only increase casting yields but also improve throughput at dewax.

There were many potential contributors to the problem. The process used highly filled, highly conductive pattern and stick wax; multiple layers of low permeability prime coats and poorly controlled flash fire dewax ovens. It was imperative to determine which of these factors should be modified to eliminate mold cracking while maintaining productivity at wax injection and minimizing capital expenditures.

This paper follows the progression of controlled tests used to incrementally improve the dewaxing process. It demonstrates a testing method that can be used to quickly and accurately evaluate many factors. Data will be presented on prime coat slurries, prime coat stuccos, backup slurries, pattern wax, stick wax and dewaxing methods with respect to dewax performance.