SAND CASTING • Sand casting is one of the earliest forms of casting practiced due to the simplicity of materials involved. It still remains one of the cheapest ways to cast metal because of the same simplicity. • In this casting process apattern is made in the shape of the desired part. This pattern is made out of wood, plastic or metal. Simple designs can be made in a single piece or solid pattern. • The patterns are then packed in sand with a binder, which helps to harden the sand into a semi-permanent shape. • Once the Sand mold is packed, the pattern is removed leaving a hollow space in the sand in the shape of the desired part. • The pattern is intentionally made larger than the cast part to allow for shrinkage during cooling.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
• Sand casting is one of the earliest forms of casting practiced due to thesimplicity of materials involved. It still remains one of the cheapest ways tocast metal because of the same simplicity.
• In this casting process a pattern is made in the shape of the desired part.This pattern is made out of wood, plastic or metal. Simple designs can be
made in a single piece or solid pattern.
• The patterns are then packed in sand with a binder , which helps to hardenthe sand into a semi-permanent shape.
• Once the Sand mold is packed, the pattern is removed leaving a hollowspace in the sand in the shape of the desired part.
• The pattern is intentionally made larger than the cast part to allow forshrinkage during cooling.
• Cores can then be inserted in the mold to create holes and improve the
casting's net shape.
• Two piece molds are clamped together and melted metal is then poured into an opening, called RUNNER. If necessary, vent holes, called RISERwill be created to allow hot gases to escape during the pouring.
• The pouring temperature of the metal should be a few hundred degreeshigher than the melting point to assure good fluidity, thereby avoidingprematurely cooling, which will cause voids and porosity.
• When the metal cools, the sand mold is removed and the workpiece isready for secondary operations, such as machining & plating.
• Sand casting is the least expensive of all of the casting processes.
Between 1875 and 1940, cast iron cookware manufacturers
periodically refined their casting techniques to produce extremelywell-made products.
Products made between 1900 and 1940 were both slightly thicker andmore finished in their appearance.
During same time, the manufacturing included a series of polishingsteps that produced pieces with glass-like surfaces.
The development of new technologies and an increased demand forcast parts gave tremendous impulses to the metal casting industry .
During 19 century iron casts was not only limited to the creation of cookware and decorative objects but was also used for the productionof machine parts and articles of daily use.
"Green sand" is a mixture of wet silica sand, clay, moisture and other locallyavailable additives.
The “Air set sand" method uses dry sand bonded to materials other thanclay, using a fast curing adhesive. When these are used, they are collectivelycalled "air set" sand castings to distinguish these from "green sand" castings.
Molding sands are natural bonded (bank sand) and synthetic (lake sand),which is generally preferred due to its more consistent composition.
With both methods, the sand mixture is packed around a master "pattern"forming a mold cavity.
The sand mixture is tamped down as it is added, and the final moldassembly is sometimes vibrated to compact the sand and fill any unwantedvoids in the mold.
Air-set molds often form a two-part mold having a top and bottom, termedCope and drag.