Vacuum molding is an another kind of casting process for metals, along with sand casting and shell molding. It has very specific process parameters and some advantages and disadvantages that results from these parameters and properties. In here, we explain process steps of vacuum molding and advantages and disadvantages of vacuum molding below.
In general, cope-drag patterns are used in vacuum molding processes. Upon cope and drag patterns, a thin and heated plastic film is drawn over. On pattern, small holes are opened to apply vacuum on this thin film to attach it on pattern. After this, flask is attached to the pattern that thin film is attached. Then this flask is filled with dry sand.
Upon this sand, thin plastic film sheet is drawn out again. And vacuum is also applied on this thin film. Pouring cup and sprue must be designed inside the sand.
After the vacuum application, sand is packed between these two plastic and vacuumed films. And required sand mold is obtained.
Cope and drag sides of sand molds are obtained with this method. Then these cope and drag sand molds are attached to each other. Then the liquid metal is poured inside the mold cavity. The plastic film is burned and the vacuum casting is established.
Most people think that vacuum application in vacuum molding process is about the application of vacuum on liquid metal. But as you understand that, the situation is not like this. Vacuum is used to produce molds from dry sands.
The most important advantage of vacuum molding process is, there is no use of water and binders in mold making. Sand stays dry during the molding stage. This means that the reconditioning the sand for further casting operations is very easy.
Also because of there is no moisture inside the mold, there is no defects that originated from the moisture.
The disadvantage of this process is, mechanization of whole vacuum molding process is hard to apply it as serial production. Vacuum applications are relatively slow to application of serial manner.
These are the general features of vacuum molding proces. Do not forget to leave your comments and questions about vacuum molding process below.
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