The increasing complexity of the precision investment casting parts presents challenges within the shell building process, especially around shell drying. This can result in increased scrap or rework in the form of excess metal, finning or even foundry run-outs.

Current methods of measuring dryness include temperature, humidity, conductivity and weight loss. However, none of these methods are capable of measuring dryness of the internal passages with acurate, repeatable results.

With the development of a new method for measuring dryness, an investment casting foundry will now have the ability to measure both temperature and relative humidity in the inner passageways during the shell building process. This device can assist shell room personnel in establishing a shell building process or as a tool to identify variation during drying.

This paper will provide a comparison of current drying measurement systems against the newly created RH sensor. In addition, Selmet will demonstrate the application of this device by using it to assist in the establishment of optimal drying conditions for a newly constructed drying tunnel.