Vacuum Expendable Pattern Casting (V-EPC)

Vacuum Expendable Pattern Casting (V-EPC) is a kind of casting process that combines lost foam casting and vacuum casting. The basic principle of casting process is bond and combine the foam models which have the same size and shape to model clusters, after brushing on refractory coating and drying them, they are buried in dry quartz sand for vibration molding. Under negative pressure, the metal liquid is poured in, causing the models to vaporize. The liquid metal occupies the position of models and solidifies and cools to form the castings.

The Process Flow of Vacuum Expendable Pattern Casting

* Making Foam Plastic Models

Polystyrene foam plastic is selected as the model material.It is necessary to ensure that it has excellent internal quality, no incomplete bonding or loose defects, and appropriate density and strength. The mold is fabricated by combining electric heating wire cutting with manual polishing to guarantee the accuracy of the dimensions.

* Coatings and Coating Processes

To enhance the adhesion between the outer surface of the foam plastic mold and the gating system, specific coatings need to be applied. Usually, water-based coatings are selected and improved by adding surfactant and other additives to ensure good coating adhesion, high strength, and certain breath-ability.

* Sand-molding Steps:

Use dry sand without binder for molding. The mold should have good air permeability, uniform and sufficient compactness. Use single quartz sand as the molding sand and strictly control the temperature of the molding sand during the sand-molding process to prevent the mold from deforming.

* Negative Pressure Pouring:

During the pouring and cooling process, a certain negative pressure level needs to be maintained. Usually, a vacuum pump is used to keep the negative pressure state of the mold. When the negative pressure level of the mold remains above 0.025 MPa, the mold can exhibit sufficient strength.

Features and Application of Vacuum Expendable Pattern Casting

• Casting without flashes,burrs and draft angels since there is no need of model taking, no parting surface and no sand core.
• Raw casts are with precision dimensions, good surface texture, well production efficiencyand good property.
• It is suitable to the complex-shape metal parts, especial to the production of wear resistant steel parts.

Through research on vacuum expendable pattern casting, it can be seen that V-EPC not only improve the cast quality and production efficiency, but also widely applied in the production of required high precision and complex-shape metal parts.