Investment casting is a very important metal casting process that has very specific process parameters compared with other meta casting processes such as sand casting, expandable mold casting etc. In here, we explain the general process steps and parameters of investment casting, advantages of investment casting and disadvantages of investment casting.
In investment casting, a special wax patterns must used. And mold cavity for liquid metal is obtained with this wax patterns.
Bunch of wax patterns are obtained by using a special wax material, by master die which gives the net shape of wax pattern. Master die must be designed with the allowances of shrinkages, which are the prominent problems in general metal casting operations. These obtained wax patterns are combined each other with the wax branches, which will constitue the sprue and gating systems. With this system, bunch of metal parts are produced in one investment casting process.
A slurry that includes fine silica grains which are mixed with bonding agents is prepared for coating of obtained wax pattern. This slurry must be refractory to withstand higher temperatures due to molten metal. The prepared pattern is dipped into this slurry.
When the pattern is coated with refractory slurry, it is left into special owens for some hours to solidification of coating on wax pattern. The name of ‘invesment’ is come from this step. The wax model is ‘invested’ into slurry.
After the solidification, heat is applied to this wax and solid refractory to melt wax inside the refractory mold. When the wax is melt, the mold from refractory material is obtained.
Once the refractory mold is obtained, molten metal is cast into this mold. And cast metal solidifies inside this mold. When the solidification of cast metal takes place, the refractory mold is broken to extract the metal parts which are combined with metal sprue system .
These sprue systems must be cleaned with required machining processes to obtain separate metal parts from ‘pattern tree’. So, a number of metal parts are obtained with one process of investment casting.
Altough the cutting of metal parts are stated above from the pattern tree, no additional machining processes required. Investment casting process is a ‘net-shape’ process, which also cuts the additional costs.
Dimensional control over produced metal parts is excellent with investment casting. So, in where the dimensional correctness is key, investment casting process is prefferable over other ones.
The wax that is used in investment casting processes can be re-used again and again through solidification and melting between processes.
Investment casting process is suitable for small and intracate parts such as accesories and various important small metal parts.
The surface characteristics of obtained metal parts from investment casting are excellent again. Dimensions about +-0.075mm can be obtained with investment casting method.
Actually, invesment casting is a very special process for special types of metal parts. Almost every kinds of metal materials can be cast in investment casting. Because of the time, equipment and workforce requirements in investment casting make it an expensive metal casting process among others.
These are the general characteristics of investment casting method. Do not forget to leave your comments and questions about invesments casting method below.
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