The term 'investment casting
' refers to a process for making machine parts, tools and other precision metal instruments that are cast in wax; the wax is then dipped in ceramic. After the ceramic dries, the wax is burned away. The resulting mold can make up to 50,000 identical pieces, according to American Casting Foundry. This was once a lengthy and expensive process, but new production flow methods have made the process much faster and more affordable.
1.Obtain a steel prototype of the product that has been made to exact specifications. Investment casting makes precise replicas, so make sure the prototype perfectly represents the piece that will be manufactured.
2.Create an aluminum die or mold of the piece to be manufactured. Coat the prototype with a thin layer of grease, then place it halfway into the molten aluminum alloy; allow the aluminum to cool. The greased prototype lifts out easily from the dried aluminum mold. Place the other half of the prototype in molten aluminum and allow it to cool. The result is two halves that, when put together, form a negative image of the prototype. The halfway marks must be carefully measured so that you know the resulting mold halves represent the exact size of the prototype when placed together. Check the die for any flaws or inaccuracies.
3.Melt the metal alloy you're using to make the final part. Start the melting process as you make the aluminum die so the the metal alloy will be ready to pour when you need it.
4.Make wax patterns from the aluminum die. Pour the wax into the die and let it dry. This is a wax duplicate of the prototype.
5.Dip the wax in liquid ceramic. Let the ceramic dry for 48 hours. Melt out the wax by placing the ceramic/wax piece in an electric furnace at 180 degrees to 250 degrees Fahrenheit. Pour out the wax: You have a shell you'll pour the melted metal alloy into.
6.Pour the liquid metal alloy into the ceramic mold. Allow the alloy to become solid, then break away the ceramic mold. The resulting part is your final product.
7.Inspect the final product. Any corrections that require tooling --- using fine metal files, awls or chisels to remove imperfections --- should be made at this stage. Flawed pieces should be discarded.
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