Using soluble cores in investment casting

Do your metal components require complex internal cavities?

Investment casting is ideal for parts requiring tight tolerances, repeatability and complex design features. For parts requiring particularly complex internal cavity configurations, our design engineers can incorporate a soluble core into the investment casting process. The use of soluble cores allows more intricate cavity patterns to be included in the casting, reducing or eliminating the need for additional machining.

Designing for soluble cores

During the standard investment casting process, pattern wax is injected into the mould cavity, cooled, ejected and then attached to the sprue before proceeding through the remainder of the casting process. If the part does not require a particularly intricate core, this process is automated using our state-of-the-art technology. If the part requires an internal channel, the soluble core process is best performed by one of our specialised operators.

First, soluble wax is injected into a mould to form the core geometry. The core is then ejected from the mould and cooled.

An operator mounts the soluble core in a precise position within the mould cavity for the complete component. The soluble core position within the mould is maintained by support points incorporated into the mould during the design process. This additional support ensures the core remains in place when pattern wax is injected and helps facilitate wax removal from the mould. The mould is then closed and pattern wax is injected into the cavity around the soluble core. Within the mould, the soluble core creates the internal baffles, channels and ports that will be included in the final casting.

Once the pattern wax has cooled, the complete part is ejected from the mould. The part is then placed in a bath of mild hydrochloric acid, where the soluble core is dissolved, leaving a geometrically complex core that cannot otherwise be achieved through standard investment casting.

The remaining pattern wax is then attached to the sprue and continues through the remainder of the investment casting process as normal. The end product is a repeatable, intricate part that delivers high performance without requiring costly secondary operations.

Why use soluble cores?

Using soluble cores provides many benefits, with the main benefit being the ability to design components with greater complexity in the part core without costly secondary operations.

Without the need for additional machining, engineers have greater design freedom. In addition, eliminating secondary operations saves manufacturing time and, consequently, manufacturing costs.