Shell mold casting is a metal casting process to create custom metal parts, similar to sand casting. Shell casting creates a durable mold formed by applying a heat-resistant material around a reusable pattern, which is then heated and filled with molten metal to produce accurate metal components. During the shell mold casting process, the mold is a thin hardened shell of sand as well as thermosetting resin binder, propped up by other materials. Compared to sand casting, the shell moulding process features better dimensional accuracy, a higher productivity rate, and lower labor involvement. Plus, it must be pointed that there are much difference between the sand casting process and shell molding process.
Although sand has been used in both shell moulding process and sand casting process, the later forms a cavity inside the sand in a flask. In the stark contrast, in the shell moulding process, a mold can be created by using the sand mixed with a bonding resin so as to cover a heated pattern. Using the shell mould casting process, many parts or components are produced, including cilinder heads, bushings, gears, valve bodies, and so on.
Although it sounds complicated, shell moulding process is a relatively simple process consisting of the following steps. I will describe each step in more detail.
STEP 1: Creating the Pattern
In the course of the shell moulding process, the first step is to create a shell moulding pattern. Different factories use different techniques to manufacture the pattern. But, essentially, these factories have the same goal – to manufacture a shell moulding pattern resembling very much with the part or component to be cast.
In the shell moulding process, the pattern typically is composed of two pieces of different metals, namely iron or steel in the shape as desired for the finished part or component. Apart from steal and iron, other materials are often used, such as aluminum for production in low volume or graphite to cast the reactive materials.
STEP 2: Creating the Mold
Once the shell moulding pattern is ready, it is high time to prepare some of the resin-coated sand. Meanwhile, the temperature should be set at around 550 degrees F. The pattern is heated to around 550 degrees F and covered in sand. And then, the resin-coated sand grains will bind together and begin to sedam and solidify.
After several minutes, there are enough sand bonding against the corebox walls. At this time, you could pour out the rest of the sand, leaving a hollow core. Generally speaking, the sand walls of a shell mold ranges from 7 to 8mm thick.
STEP 3: Assembly of Shell Mold
In the shell mould casting process, the shell mold is complete only after the two shell halves are joined totally by using glue or other fasteners and securely clamped.
When both the core and the shell mold are ready, it is about time to assemble them. The shell mold is removed from its pattern and the core from its corebox. The two halves are tightly sealed by using glue or glue in company with other fasteners.
If there is a need to insert a core, they should be inserted preceding closing the mold. And then, the shell mold will be placed into a flask and propped by a piece of backing material.
STEP 4: Pouring
The fourth step in the shell casting process is to pour molten metal into the shell mold’s cavity. In the shell casting process, metals and alloys come in different types, such as steel and iron. No matter what kind of property, the metals or alloys will be heated into a liquid state, which then will be poured into the shell mold’s cavity, forming a hardened shell.
One point that should be pay attention to is that metals or alloys must be heated to extremely high temperatures within the shell moulding machine. The specific temperature dependents on the types materials. For example, the steel alloy is usually poured at 3,000 degrees F. Plus, once poured, the fluid metal must experience several minutes’ standing until it’s solidified.
STEP 5: Cooling
Following the above step, the molten metals are allowed to cool and solidify into the shape of the final shell casting process. Generally speaking, the pattern parts should be chilled at the room temperature. Accompanying the cooling of pattern parts, the molten metal will gradually become a tough shell.
STEP 6: Removing Shell Mould Casting
In the shell casting process, this is the last step – removing shell mould casting. After the molten metal has chilled, the outer mold can be broken up and the casting taken out. Before such a process, attempts should be made to trim and clean processes to remove the redundant metal from the feed system and sand from the shell mold.
The shell casting process involves the using of a two-pieced pattern, the shell mould casting is easily ejected by “opening” the pattern. With the top and bottom pattern parts are separated from each other, the newly created shell casting can be simultaneously ejected.
If you feel that the shell casting process might be right for you, or you want to learn more information about the shell moulding machine, the best way to proceed is to reach us directly or leave your comments below. The DaWang Casting can cooperate with you to come up with the best, most cost-effective way to proceed. You can rest assured that DaWang Casting will not charge you for a quote and consultation. Moreover, we provide the shell moulding machine at best prices. Sincerely welcom your consultation and order.