Omnidex has been providing shell casting services to our business customers for many years. We work with the industry’s best to bring you a range of high quality casting solutions. If you are looking for an efficient sand mold casting method with high consistency, our Shell Mold Casting process can definitely meet your needs.
Shell Mold Casting is a metal casting process, similar to sand casting in which molten metal is poured into an expendable sand-based mold. However, in shell mold casting, the mold is a thin-walled shell created by applying a sand-resin mixture around a pattern.
The pattern, a metal piece in the shape of the desired part, is reused to form multiple shell molds. Reusable patterns allow for higher production rates, while the disposable molds enable complex geometries to be cast.
Compared to sand casting, shell casting has better dimensional accuracy, a higher productivity rate, and lower labour requirements. shell casting is often used for small to medium parts that require high precision
A two-piece metal pattern is created in the shape of the desired part, typically from iron or steel. Other materials are sometimes used, such as aluminium for low volume production or graphite for casting reactive materials.
Each pattern half is heated to 175-370 °C and coated with a lubricant to facilitate shell removal. The heated pattern is clamped to a dump box, which contains a mixture of fine silica sand and a thermosetting phenolic resin binder.
The dump box is inverted, allowing this sand-resin mixture to coat the pattern. The heated pattern partially cures the mixture, which forms a shell around the pattern.
Depending on the time and temperature of the pattern forming process, the thickness of the shell is 10 to 20 mm. Each pattern half and the surrounding shell is cured to completion in an oven giving it a tensile strength of 350 to 450 psi, and then the shell is ejected from the pattern.
The two shell halves are joined together and securely clamped to form the complete shell mold. If any cores are required, they are inserted prior to closure. The shell mold is then placed into a flask and supported by a backing material.
The mold is securely clamped together while the molten metal is poured from a ladle into the gating system to fill the mold cavity.
After the mold has been filled, the molten metal is allowed to cool and solidify into the shape of the final casting.
After the molten metal has cooled, the mold can be broken, and the casting removed. Trimming and cleaning processes are required to remove any excess metal from the feed system and any sand remaining from the mold.
Max. Wall Thickness
Solid: Cylindrical, cubic, complex
A sizable amount of casting in the steel industry uses the shell molding process, which ensures better profitability. Carbon steel, alloy steel, stainless steel, low alloys, aluminium alloys, copper, are all cast using the shell molding process.
Casting that requires thin sections and excellent dimensional accuracy is cast using this process. Truck hoods, small size boats, bathtubs, shells of drums, connecting rods, gear housings, lever arms, etc. are cast using the shell molding process.
Shell casting can be used to make complex parts with fine details and very thin sections. It also offers excellent surface finish and tight tolerances. But this is not the full extent of its capabilities.
Although both shell mold and sand casting used sand to form a mold, we mix sand with a bonding resin to create a mold when performing shell casting. This process helps to cover a heated pattern and imparts higher dimensional accuracy.
The smoother surface in shell casting compared to sand casting save your cost of machining and grinding operations. It requires fewer finishing operations that in some cases, these machining works can be eliminated as well.
What also makes this casting approach stand out from most other processes is that it can be fully mechanized and automated, and it has lower skill requirements for workers.
That means this process can have reached a higher production rate and can be easily scaled for mass production. These advantages make the casting process the ideal solution for the large-scale production of small to medium-sized high-precision parts. This process is often used in the manufacture of camshafts, crankshafts, gear housings and many more.
Omnidex, as an ISO 9001 certified manufacturing company, provides excellent shell mold castings at a competitive price in China and Vietnam.
Contact our Customer Service and let us know how we can help to catapult your next project to success.
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