Study on the surface roughness of ceramic shells and castings in the ceramic shell casting process based on expandable pattern

A method to form a thin smooth film of wax on the surface of the foam pattern was proposed by introducing the molten wax in this work. Organic smoothing coatings for the foam pattern were also prepared and their effects on the surface roughness of the foam patterns, shells and castings were investigated. Effects of the facecoat slurry used to fabricate ceramic shells on the surface roughness of the shells and castings were studied. The analysis of results indicates that the surface smoothing coatings and the wax smoothing film both greatly decreased the surface roughness of ceramic shells and castings from 3.2–6.3 μm to 0.8–2.5 μm (Ra), and the surface roughness of shells and castings would be improved if the facecoat slurry is prepared with finer filler materials.