Buoyancy Effect Of Core In Sand Casting Operations
Shell molding is an also prominent metal casting process apart from sand casting. Shell molding has its own distinct process parameters, that comes with some advantages and disadvantages. In here, we explain these process parameters, steps and advntages/disadvantages of shell molding process.
In sand casting, obtaining of mold structure is very tough and requires lots of works to done, and needs engineering level design, around lots of parameters. But in shell molding, the mold is made from very thin shell to obtain mold cavity. Again, sand is used, but thermosetting resins are used as binders in shell molding.
Inside a box, there is sand that mixed with thermosetting resin. This box is called as ‘dump box’. The open side of this box is closed with the metal pattern that has the same shape with metal cast product. And this metal pattern is clamped on the dump box. Metal pattern is also heated to a sufficient temperature to cure the resin.
The dump box is inverted, and sand with mixed with thermosetting binder falls on the heated and clamped metal pattern. Heat on this patten cures a thickness of sand. After the required thickness obtained along sufficient time, the dump box, re-inverted to its previous position. So a thin wall of sand is obtained on the metal pattern.
This obtained thin shell is heated inside a owen to obtain much more rigid mold structure.
Two of obtained thin shells are combined to each other to obtain a full shell mold inside a flask. They are clamped to each other and the space between flask and thin shell is filled with metal show or sand for supporting purpose.
Liquid metal then is poured inside this prepared shell mold. After the solidification, shell is removed then part is obtained.
The most important advantage of shell melding is the superior surface characteristics are obtained. Compared with sand casting operations, very good surface characteristics can be obtained. Dimensional contol over cast product is also superior. For small to medium sized parts, very good dimensional characteristics can be obtained. Even unlike sand casting operations, generally no need for further machining operations to obtain desired surface and dimensional characteristics.
The main disadvantage of shell molding is the production of mold is expensive compared with sand molding. And also, the best performance from this application can be obtained from production of small parts. Mechanized and serial production manner is much more suitable for shell molding applications.
For example, camshafts, gears, valve bodies and bushing can be produced with shell molding operation.
These can be a general explanation of shell molding applications, advantages, disadvantages and process steps. Do not forget to leave your comments and questions about shell molding and their process parameters below.
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