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by : Kent Klein

There are various casting processes being implemented nowdays. The oldest amongst them is sand casting. Spin casting is also widelyused. They can be described as follows:

Sand Casting: Sandcasting involves formation of mold from a mixture of sand and to pour a castingliquid, most probably, a molten metal into mold. The metal is then allowed tosolidify and the removal of mold, takes place. Sand molding consists of twotypes: green sand method and air set method. The first one consists of mixtureof clay, moisture, silica, and many other additives. The second one consists ofmixture of dry sand and other materials, not moist clay. They are mixed withthe help of a quick curing adhesive. The collective use of these materials iscalled ‘air set’.

At times, there is temporary plug placed to pour the fluidwhich is to be molded. Air-set molds usually form molds consisting of twoparts-the bottom and the top. The mixture of sand gets tamped down after itsaddition. It does not generate any by-product. After the solidification andcooling of metal, the mold gets usually destroyed. This is because its removalinvolves a lot of breaking and cracking. The casting accuracy depends a greatdeal on the sand and the process of molding used. Castings composed of greensand result into formation of rough texture on casting surface, and thischaracteristic makes them easily recognizable. Air-set molds produce smoothercastings.

Many a times, the casting process results in losing ofcomponents of sand mixture. It is possible to reuse green sand by the way ofadjusting the composition to get the lost additives and moisture replenished.The entire pattern itself is eligible to be reused for producing novel sandmolds. The method of reuse can be continued for an indefinite period. In 1950,casting process got automated partially. They have been in great demand fordeveloping production lines since then.?

Spin Casting: SpinCasting is better known as Centrifugal Rubber Mold Casting (CRMC). It impliesutilization of centrifugal force for producing castings out of rubber mold. Asa 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 usuallythermoset plastic in the liquid form or a molten metal. It gets poured into themold through the opening at its centre. Corresponding to the solidification ofmetal, or the setting of thermoset plastic, the spinning of the filled moldtakes place.

Normally, organic rubber or vulcanized silicone is used as amold-making substrate in spin casting. Vulcanization takes place in the middleof process of mold-making. After the successful completion of vulcanizationprocessFree Articles, venting and gating must be undergone by the mold. This implies carvingof channels for ensuring proper material flow and air during the course ofcasting. A scalpel or knife is used to carry out the above two processes. Themold complexity is directly proportional to the time required in implementationof venting and gating.??