Application and Limitations of Investment Casting in Precision Machining

Investment Casting by Ben Machine

Precision machining takes investment casting from a 5000-year-old art form to the technology behind some of the most complex machine components in the world.

Casting for a Solution

There are multiple scenarios where investment castings can be part of a precision machining solution:

  • Large parts that require the milling away of huge amounts of raw material benefit from being cast and then precision machined to extremely tight tolerances and needs.
  • This can reap significant savings both in materials and in precision machining time.
  • Complex, hidden geometries that require separate parts to be machined and then joined together can be more efficiently made by casting the components as one and machining the resulting part into the finished product.
  • Parts like turbine blades or advanced heat sinks may require internal porting or cooling channels which can’t be machined.
  • Cores can be used to create shaped interior spaces for other parts. Investment casting can accommodate those structures, then precision machining can refine the outer features.


Cost Savings with Precision and Technology

Ben Machine started operations producing precision machined moulds used to create the wax forms for casting – that’s a half-century of experience working in the investment casting industry. We have institutional knowledge of how castings will behave in the foundry, and on the machine. Our machine shop experts know where supports and hold-down tabs need to be added to make the casting easier to machine. Without proper design and placement of these features, finish machining will take longer, cost more, and usually result in a lower quality product.

Casting houses on their own often don’t understand those details or are focused strictly on the casting process, missing the difficulties encountered with the machining process. Working directly with the machine shop from the beginning can save money on the design itself. Our machining experts, for example, know where walls can be made thinner to save further machining, reduce weight, eliminate material and lower costs, all while maintaining a high level of quality. Ben Machine specializes in precision machining of these types of thin-walled castings.  


When You Can’t Rely on Hard Tooling

If your needs are more time-critical, you have a small batch requirement, or you haven’t perfected your design, Ben Machine can create moulds without hard tooling using the SLA 3D printing process. This printing technology allows us to print the patterns necessary to create the cast moulds for the casting process. While it’s not as precise as patterns coming from a machined hard tool, Ben Machine has developed ways to machine these castings as close as possible so that you can test your design. A small reduction in precision can be a small price to pay for significantly quicker lead times and the elimination of high tooling costs.


Not the Answer to Every Situation

While investment casting has its place in metal manufacturing, it is not the solution for every need, the engineering requires some special skills. The wax components usually have to be formed in machined dies, which can be a high cost. Forming the cast itself takes days since each subsequent bath in the ceramic slip and stucco must be allowed to dry before the next one is applied. Following casting, each component has to undergo machine finishing. Many also must undergo specialized testing to ensure the metal contains no hidden voids or cracks. The time required for each casting makes this process an unlikely candidate for large volume production of very simple parts. But, in the right circumstances, there is no better process for precision parts.

Investment casting gives manufacturers capabilities otherwise unobtainable. When coupled with precision machining, it’s an elegant solution to some of the most difficult problems facing engineers today. Talk to our machine experts if you’d like to know whether your current or future project would benefit from the investment casting process.