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| September 2009 | Courtesy of BEGO USA |
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Casting Without a Button Sound spruing principles should always be practiced to ensure complete and precise castings. Ideal spruing includes: round wax connections, properly positioned reservoirs, and appropriate (4-5 mm) minor connectors to serve the purpose of a shut off gate to stop the reverse flow of metal back into the reservoir as the alloy cools. In the past, BEGO has talked about the concept of sectioning the reservoirs on multiple span bridges or implant cases to allow for stress-free expansion and contraction of the alloy as it cools. To take this concept one step further, you can eliminate stress by casting without a button. If the feeder sprues and the reservoirs are free to move with the large casting - as it cools, this helps to eliminate stress in the casting which could lead to warped castings and remakes. To eliminate the button, you need to know how much alloy to cast. First, weigh your wax up, including the reservoir and sprues - (add them together and) this will give you the total amount of your wax-up. If your wax button is included, weigh a wax button by itself and subtract this amount from your total. Second, you need to find out the specific gravity or density figure of the alloy you are casting. Third, calculate the exact amount of alloy needed for this casting by multiplying the wax weight by the density of the alloy. (Weight of wax-up) X (Density of the alloy) = Alloy volume needed for casting This technical tip will hopefully keep more money in your pocket and less alloy going to the refiner. |
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 For more information, call your local dealer or BEGO USA, 1.800.342.2346 www.begousa.com | |
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