What is Investment Casting

Many customers asked us what was investment casting, now we try to explain more information about it. Investment casting, also known as the lost wax casting methods, is widely used for the fooundmetal industries. This articel mainly introduce the brief information of the investment casting methods.

How the Lost Wax Process Works

In investment casting, a shape is formed (usually out of wax) and placed inside a metal cylinder called a flask. Wet plaster is poured into the cylinder around the wax shape. After the plaster has hardened, the cylinder containing the wax pattern and plaster is placed in a kiln and is heated until the wax has fully vaporized. After the wax has fully burnt-out, the flask is removed from the oven, and molten metal is poured into the cavity left by the wax. When the metal has cooled, plaster is chipped away, and the metal casting is revealed.

When is Casting the Appropriate Process?

Casting is very useful for creating sculptural objects or engineering shapes with complex geometry (such as transmission housings) in metal. Cast parts have a unique look to them, quite different from machined parts. Some shapes which would be difficult to machine are more easily cast. There is also less material waste for most shapes, since unlike machining, casting is not a subtractive process. However, the precision achievable through casting is not as good as machining.

When Should You Choose Investment Casting and When Should You Choose Sand Casting?

One big advantage of investment casting is that it can allow for undercuts in the pattern, while sand casting does not. In sand casting, the pattern needs to be pulled out of the sand after it is packed, whereas in investment casting the pattern is vaporized with heat. Hollow castings and thinner sections can also be made more readily with investment casting, and a better surface finish is generally achieved. On the other hand, investment casting is a much more timely and expensive process, and can have a lower success rate than sand casting does since there are more steps in the process and more opportunities for things to go wrong.

wax patterns for lost wax casting method

What You Should Know Before You Begin an Investment Casting Project?

Small differences in the investment casting process lead to greatly different (i.e. sometimes poor) results. Experience is great to have, but if you don’t have it, here are a few things you can do to improve your chances of success.

1. Follow instructions carefully and seek out the advice of the local investment casting experts. Investment casting is an involved process. Get help from a TA who has experience casting.
2. Pick a reasonable size casting.  Bigger projects are harder and take longer. Ring or jewelry-sized castings are on the easy end of the investment casting scale (although even smaller items become more difficult). Castings that are the size of a banana are harder, and those the size of a loaf of bread are at the upper limit of the PRL’s capabilities.
3. Start early. The process takes a long time, and castings don’t always come out. Which means if you cast your carefully crafted goat head in week 9 of the quarter and something goes wrong, you probably won’t get a second try.

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