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The important steps of investment castings process

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The important steps of investment castings process 
By megan2008 on Oct 30, 2013 05:39 AM
The investment casting process is a metal casting process where a disposable wax replica, or “pattern”, which is identical to the casting desired, is produced from an injection molding type of tool. The wax models are engineered to be slightly larger than the casting due to the volumetric shrinkage of metal when it cools from a liquid to a solid. The wax patterns are gated onto a sprue, and then repeatedly dipped into liquid ceramic slurry to form a layered, seamless mold. After the ceramic has dried, the disposable wax is melted out leaving a hollow cavity into which the metal, melted from exacting recipes to achieve the desired alloy, is poured and allowed to solidify.

The investment castings process begins with fabrication of a sacrificial pattern of the same basic geometrical shape as the intended finished cast part. Patterns are normally made of investment casting wax that is injected into a metal wax injection die.

Once a wax pattern is produced, it is assembled with other wax components on a central wax stick, called a sprue, to form a casting cluster or assembly.

The entire wax assembly is then dipped in a ceramic slurry and covered with a sand stucco, and allowed to dry.

The dipping and stuccoing process is repeated until a shell of ~6-8 mm (1/4-3/8 in) is applied. Once the ceramic has dried, the entire assembly is placed in a steam autoclave to remove most of the wax. The remaining amount of wax soaked into the ceramic shell is burned out in a furnace.

At this point, all of the residual pattern and gating material is removed, and the ceramic mold remains. The mold is then preheated to a specific temperature and filled with molten metal, creating the valve castings.

Once the casting has cooled sufficiently, the mold shell is chipped away from the casting.Next, the gates and runners are cut from the casting.After minor final post processing (sandblasting, machining), the castings - identical to the original wax patterns - are complete and ready for shipment.

automotive castings manufacturers: http://www.ftm-china.com/product/automotive-castings.html
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