Holes, slots and narrow passageways are an inherent feature in investment cast parts. However, these intricate details occasionally make construction of the ceramic shell challenging. Ceramic or soluble cores may be placed in wax patterns in order to create internal geometries in the shell that will be present in the final part. While the use of ceramic and soluble cores is widely used, it is not always feasible or cost effective for many parts with internal geometries.

When cores are not used, shell-building internal geometries can be tricky. Shell bridging may occur in areas with narrow passageways or small holes. This can create issues with building sufficient shell thickness in these areas. It can also affect drying. Both can lead to metal penetration during pouring, creating rework or scrap in the process.

This paper will discuss methods available to investment casters utilizing pourable core materials. Proper application techniques and common issues will be addressed, along with case studies analyzing the process and economic benefits obtained utilizing available core materials.