What is Investment Casting ?

(Last Updated January 17, 2020)

 

Investment casting, similar to Lost-Wax casting, is thousands of years old. Documented for the first time around 1100 A.D.by a monk named Theophilus Presbyter, the term “investment” refers to the mold being filled or invested with metal. Investment casting was originally used to produce decor, religious statues, and jewelry. This casting process eventually made its way to the industrial revolution and became a favorite method of Dentists for creating crowns and inlays. Investment casting is still used today to produce intricate castings with brilliant, smooth finishes.

 

Investment casting process

Investment casting is a method of casting in which a mold is created, and can be done in 6 steps.

Creating a pattern

-Patterns are made from wax (though some use plastics) using a metal injection die.

Assembling the wax patterns with the tree

-Once the pattern is created, it will be assembled with other components to create a gate and runner metal delivery to create the casting.

-Depending on the finish component size and configuration, multiple wax patterns can be processed on one tree.

Mold shell

-Once the wax pattern is assembled it gets dipped in a ceramic slurry then covered with sand stucco and given time to dry.

-If necessary cycles of wet dipping and stuccoing are repeated until you acquire the desired shell thickness.

-Once the ceramic shell has dried, it has become strong enough to retain molten metal during the casting process.

Wax Removal

-The assembly is put inside a steam autoclave to melt away the wax.

-If any wax remains it will be burned out in a furnace. Once all the wax has been removed, the cavity with the shape of a desired cast part.

Melt and cast

-The mold is preheated to a temperature that is specific and then filled with molten metal, creating your desired metal casting.

Final touches

-When the casting has cooled, the mold shell is broken from the casting in a knockout operation.

-If necessary the gates and runners are cut from the casting, and if necessary it will be sandblasted, ground, and machining is performed to finish the casting dimensionally.

 

Pros and Cons

As mentioned previously, investment casting is ideal for creating intricate patterns. Metal castings made using the investment process can be made very thin and with great accuracy. The hard molds of investment casting also allow for a smoother surface to the final product. However, there is a negative aspect to investment casting: though the wax can easily be reused time and time again, the ceramic shell, once used, is lost. This makes the process more complicated and more expensive. Although some of the investment casting processes can be automated, much of the procedure still needs to be executed manually. But, once the process is complete, investment casting products do not need any secondary processing to be ready for use.

 

Invest in General Kinematics

General Kinematics is a great investment for any casting process or pattern. With over half a century of experience and a track record for reliability, GK can improve the performance of your metal casting process. Ask a GK Engineer how we can automate your work-flow today, check out our metal casting equipment, or read the stories of others in the metal casting industry that have used (and loved!) GK equipment to improve their process. 

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