A renewed sand mold casting method that enables higher precision and automation

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.

What is Shell Mold Casting?

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

Shell Mold Casting Process

Shell-Mold-Casting-Process Illustration_Metal Casting Services_offshore Manufacturing_OmnidexCastings
Shell Mold Casting-Process Illustration

1. Pattern Creation

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.

2. Mold Creation

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.

3. Mold Assembly

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.

4. Pouring

The mold is securely clamped together while the molten metal is poured from a ladle into the gating system to fill the mold cavity.

6. Cooling

After the mold has been filled, the molten metal is allowed to cool and solidify into the shape of the final casting.

5. Casting Removal

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.

Shell Mold Casting Capabilities

Typical

Feasible

Quantity

1000-1000000

100-1000000

Tolerance

±0.015 in

±0.006 in

Surface Finish

50-300 µin

30-500 µin

Max. Wall Thickness

0.06-2.0 in

0.06-2.0 in

Part Size

0.5-220 lb

0.5-220 lb

Shapes

Thin-walled: complex

Solid: Cylindrical, cubic, complex

Flat

Thin-walled: Cylindrical

Thin-walled: Cubic

Shell Mold Casting Materials

Shell casting works effectively with a variety of metals and metal alloys. Typical alloys used in this better dimensional tolerances and surface finish casting are aluminum, nickel and copper in non-ferrous metals, and steel, carbon steel as well as cast iron in ferrous metals

You can get more information about the alloys we support here.

Ferrous metals

Non-ferrous metals

Advantages and Disadvantages of Shell Mold Casting

Advantages

Disadvantages

Shell Mold Casting Applications

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.

Unique advantages of the Shell Casting 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.

Tolerance table

Shell Mold Casting Tolerance Table_Metal Casting Services_OmnidexCastings

Omnidex, as an ISO 9001 certified manufacturing company, provides excellent shell mold castings at a competitive price in China and Vietnam. 

For further information about our casting services and capabilities, contact us via email or submit an enquiry form for a quick quote.

We are always ready to help with your latest project.

Contact our Customer Service and let us know how we can help to catapult your next project to success.

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