A Guide to Precision Investment Casting & CNC Machining


For engineers, designers, and B2B buyers, the ultimate goal is almost always the same: a high-quality, complex part that meets exact dimensional tolerances, all at a competitive cost.

The challenge is that very few manufacturing processes can achieve both complex shapes and critical precision at the same time.

This is where the two-part solution comes in. The most efficient way to produce a high-performance metal component is not with one process, but with a combination of two: precision investment casting and CNC machining.

This guide explains how these two processes work together to create a perfect part.

Part 1: The Foundation — Precision Investment Casting

Precision investment casting, also known as the lost wax casting process, is the foundation. This process is famous for its ability to create "near-net-shape" components—parts that come out of the mold very close to their final 3D shape.

What investment casting does best:

  • Complex Geometries: It's the #1 choice for creating intricate parts with internal channels, thin walls, curved blades (like impellers), or complex housings.

  • Material Variety: It works with almost any alloy, from stainless steel and carbon steel to high-performance superalloys.

  • Reduces Waste: Instead of cutting a 10kg block of metal down to a 2kg part, you are only using the 2kg of metal you need.

But "near-net-shape" is not "finished-shape." For a part to fit perfectly into a larger assembly, it needs to be perfected.

Part 2: The Finish — Precision Machining

This is where CNC machining comes in. Precision machining takes the high-quality, near-net-shape part from the foundry and perfects the critical surfaces.

What CNC machining does best:

  • Achieving Tight Tolerances: It creates the critical mating surfaces, flange faces, and bores that must be perfectly flat or round to an exact dimension.

  • Adding Critical Features: It drills and taps (threads) holes for bolts, creates O-ring grooves for seals, and cuts features that are too small to be cast.

  • Creating a Perfect Surface Finish: It can mill or turn a surface to be perfectly smooth for a bearing or other moving part.

A part is rarely just cast or just machined. The best parts use precision investment casting to create the complex shape and precision machining to create the critical tolerances.

The "Single-Source" Advantage: Why Your Partner Matters

The biggest mistake B2B buyers make is splitting the process. They hire one of the investment casting manufacturers to create the raw part, then ship it to a separate machine shop to be finished.

This creates a logistical nightmare. It adds cost, doubles your lead time, and creates a "blame game" when a part is out of spec (the foundry blames the machinist, and the machinist blames the foundry).

The solution is to choose a "single-source" or "foundry-to-finish" partner.

Top-tier investment casting manufacturers are not just foundries; they are full-service engineering partners with an in-house CNC machining shop.

This combined model is better because:

  1. It's Designed for Machining: The foundry team knows exactly how much material to leave on a critical surface for the CNC team to machine off. The entire process is designed to work together.

  2. Total Accountability: There is one company responsible for the part's final quality.

  3. Lower Total Cost: You save on shipping, reduce scrap, and get a finished, "ready-to-use" part faster.

Conclusion

To achieve true precision, you need both processes. Precision investment casting (or lost wax casting) gives you the complex shape, and CNC machining gives you the final, tight tolerance.

The key to a successful project is finding a manufacturing partner who has mastered both processes under one roof.

Frequently Asked Questions (FAQs)

Q1: What is the difference between "lost wax casting" and "precision investment casting"?
A: They are the same thing. "Lost wax casting" is the traditional name for the process (because the wax pattern is "lost" or melted out). "Precision investment casting" is the modern, industrial term for the same process, emphasizing its high accuracy.

Q2: What tolerances can casting achieve alone vs. with CNC machining?
A: As a general rule, precision investment casting alone can achieve tolerances of around +/- 0.1mm to 0.5mm, depending on the part's size. By adding precision machining, you can achieve critical tolerances as tight as +/- 0.01mm on specific features.

Q3: Why should I care if my investment casting manufacturer has an in-house machine shop?
A: Because it saves you time, money, and risk. A manufacturer with in-house CNC machining, like Godani Export Pvt Ltd, takes full responsibility for the entire part, from the foundry to the finished, "ready-to-use" component. This eliminates the errors and delays of using two separate suppliers.

Contact Us

Ready to get a quote for your next high-precision component? Contact our engineering team. We are a single-source solution for all your casting and machining needs.



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