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PLASTIC FULL MOULDING PROCESS AND ITS ADVANTAGES

 In this method, a polystyrene foam pattern, complete with sprues, bottom gates, runners, and risers, and coated with a suitable mold wash is rammed up in a flask filled up with no bake type of sand. For small-sized castings furan or alkyd isocyanate while for medium and large-size castings CO2, ferro silicon may be used. When the molten metal is poured through the sprue, the heat from the molten metal vaporize the pattern and consequently displacement of the pattern material takes place by the molten metal. The amount of gas produced is so small that it can easily escape through the sand without causing any back pressure. However, shapes with high dimensional accuracy can be cast quickly and inexpensively by this method. 


Full Mold casting


The advantages of this process are :

1. High Dimensional Accuracy is obtained.

2. Defects such as blow holes and pin holes are eliminated.

3. There is no limitation as regards size, shape or complexity.

4. Suitable and economical for large-scale production of small castings of both ferrous and      non-ferrous metals. 

5. The rate of production is very quick as a large number of  patterns can be molded                  together.

Limitations of  this process are :

1. Precise control at all stages of production is required.

2. The raw materials, equipment and technology required are expensive.

3.Additional cost of cleaning castings for trimming gates, sprues and risers is involved. 


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