There are various casting processes being implemented now days. The oldest amongst them is sand casting. Metal Casting is also widely used. They can be described as follows:
Sand Casting: Metal Casting involves formation of mold from a mixture of sand and to pour a casting liquid, most probably, a molten metal into mold. Then, you wait a while and let the metal harden up so then you can remove the mold. The Green Sand Method and the Air Set Method are the two types of Sand Casting that make up Sand Molding. The first one consists of mixture of clay, moisture, silica, and many other additives. The second one consists of mixture of dry sand and other materials, not moist clay. They are mixed with the help of a quick curing adhesive. The collective use of these materials is called ‘air set’.
At times, there is temporary plug placed to pour the fluid which is to be molded. Air-set molds usually form molds consisting of two parts-the bottom and the top. After the mix of sand gets added, it also gets tamped down. It does not generate any by-product. After the solidification and cooling of metal, the mold gets usually destroyed. This is because its removal involves a lot of breaking and cracking. The casting accuracy depends a great deal on the sand and the process of molding used. Castings composed of green sand result into formation of rough texture on casting surface, and this characteristic makes them easily recognizable. In reality, studies show that molds that are air-set produce the smoothest castings.
Many a times, the casting process results in losing of components of sand mixture. It is possible to reuse green sand by the way of adjusting the composition to get the lost additives and moisture replenished. The entire pattern itself is eligible to be reused for producing novel sand molds. The method of reuse can be continued for an indefinite period. In 1950, casting process got automated partially. They have been in great demand for developing production lines since then.
Spin Casting: Sand Casting is better known as Centrifugal Rubber Mold Casting (CRMC). It implies utilization of centrifugal force for producing castings out of rubber mold. As a customary practice, a mold having shape of a disc gets spun through its ‘central axis’ at a pre-decided speed. The material used for casting is usually thermoset plastic in the liquid form or a molten metal. It gets poured into the mold through the opening at its centre. Corresponding to the solidification of metal, or the setting of thermoset plastic, the spinning of the filled mold takes place.
Normally, organic rubber or vulcanized silicone is used as a mold-making substrate in spin casting. Vulcanization takes place in the middle of process of mold-making. After the successful completion of vulcanization process, venting and gating must be undergone by the mold. This implies carving of channels for ensuring proper material flow and air during the course of casting. Your best bet for preforming the proccessed is to either use a scalpel or knife. The mold complexity is directly proportional to the time required in implementation of venting and gating.
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