Full-mould Casting

Specific casting techniques, such as full mould casting, centrifugal casting and continuous casting are applied where the product type requires it. 

Expendable pattern casting (Lost Foam/full mould casting) 3.9.6.1 Unbonded sand - Lost Foam... 

Full mould casting, 160 Furan-resin process, 143... 

Moulds withstand the pressure necessary to cause flow in rubber and transmit heat to the rubber. They are usually made of cast steel or special alloys. The blank or the slug of rubber for a mould should be of such size that it will be slightly more than the full mould cavity or cavities. Simple mould may require only about 2% excess, while small but complex moulds may need up to 25% excess rubber. 

The Lost Foam process with chemically-bonded sand, in this case also called the full mould process , is mostly used for producing middle or large sized castings, in single production or in small batch series. 

The mass flow of emissions from full mould and hollow mould casting processes are to be considered as similar. This can be seen from Figure 3.5 which shows the mass flow of organic carbon as a function of time upon pouring. Time 0 00 corresponds to the starting of the pouring. The data were collected using furan-bonded sands, both for full and hollow mould... 

Full mould process moulding technique using a foam model in chemically bonded sand, in which the model is lost upon pouring, generally used only for large castings... 

Fig. 8.19 Schematic diagram of the maulding and casting stages in the full-mould...

In deflocculated fluid suspensions based on clays, the water content is usually about 30% and the viscosity is 1 — 5 dPa s when thin-walled ware is cast, or 5 — 50 dPa s when full shapes are produced. The respective densities of suspensions are 1.65 — — 1.80, and 1.75 — 1.95 g cm . The time required for absorption of the water by the mould is in the order of minutes for thin-walled ware and hours for thick-walled ware. 

After the shell has been formed round the wax pattern and dried, it is dewaxed by heating to about 150 C and allowing the wax to run out, leaving the required shape of cavity inside the mould. Fig. 17.5. The mould is then fired at about 1000 C to attain its full mechanical strength, and the casting metal is poured as soon as the mould is removed from the firing furnace. 

At the quarter, half, three-quarter, and full stages, the vacuum tank is closed and sufficient vacuum generated to remove air bubbles from the casting. Finally, the rubber is cured at room termperature for 24 hours followed by postcuring for 10 hours at 65 C. It is necessary to cut or mould channels in the lower surface of the rubber to allow free access of resin to all areas of the mould. 

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