The difference between gray iron castings and ductile iron castings Both the gray Iron and ductile iron could be cast by sand casting process and shell molding casting process (resin coated sand). Sand casting is one of the most popular and simplest types of casting. Sand casting allows for smaller batches than permanent mold casting and at a very reasonable cost. Not only does this method allow manufacturers to create products at a low cost, but there are other benefits to sand casting, such as very small-size operations. Sand casting also allows most metals to be cast, depending on the type of sand used for the molds. Shell molding casting process is also called pre-coated resin sand casting process, hot shell molding castings or core casting process. The main molding material is the pre-coated phenolic resin sand, which is more expensive than green sand and furan resin sand. Moreover, this sand can not be recycle used. The shell molding iron casting parts have higher costs than sand casting. However, the shell molding casting parts have many advantages such as tighter dimensional tolerance, good surface quality and less casting defects.

Investment casting, which is also known lost wax casting or precision casting, refers to the formation of ceramic around the wax patterns to create a multi or single part mold to receive molten metal. This process utilizes an expendable injection molded wax pattern process to achieve complex forms with exceptional surface qualities. To create a mold, a wax pattern, or cluster of patterns, is dipped into ceramic material several times to build a thick shell. De-wax process is then followed by the shell dry process. The wax-less ceramic shell is then produced. Molten metal is then poured into the ceramic shell cavities or cluster, and once solid and cooled, the ceramic shell is broken off to reveal the final cast metal object. Precision investment castings can achieve exceptional accuracy for both small and large casting parts in a wide range of materials.

As a precision casting process, the shell making is a very critical process during investment casting. The quality of the shell is directly related to the roughness and dimensional tolerance of the final casting. Therefore, it is an important task for the investment casting foundry to choose a suitable manufacturing method for the mold shell.

In the lost wax casting process, the making of the mold shell is a key process. Casting shells made of silica sol as a binder can obtain good surface and high dimensional accuracy for castings.