Casting vs. Machining: How Each Process Works
Feature | Casting | Machining |
Process Type | Formative, molten metal is poured into a mold | Subtractive, material is cut away from a solid piece |
Precision and Tolerances | Moderate tolerances, often improved with post-cast machining | High precision, capable of very tight tolerances |
Material Waste | Minimal, excess material can often be recycled | Higher, since chips and turnings are removed from solid stock |
Production Volume and Speed | Faster and more cost effective at high production volumes | Faster for small batches and prototypes, with quicker turnaround from a CAD file |
Part Cost | Lower per unit at high volumes, higher tooling cost upfront | Cost stays fairly consistent regardless of volume |
Mechanical Strength | Strong directional grain structure, especially with centrifugal casting | Strength depends on the base material being machined |
Casting and machining are two of the most common ways to manufacture a metal component, and most parts move through some version of both. Understanding what each process actually does helps explain why manufacturers choose one, the other, or a combination of the two.
How Casting Works
Casting starts with molten metal, which is poured into a mold shaped like the finished part, or close to it. As the metal cools and solidifies, it takes on the mold’s shape, along with a grain structure formed during solidification. In centrifugal casting specifically, the mold spins as the metal is poured, using centrifugal force to push the metal against the mold wall. This produces a dense, uniform tube shape with impurities forced toward the bore. As a result, the casting has strong, consistent mechanical properties before any machining even begins.
How Machining Works
Machining takes a different approach. Rather than shaping metal in a liquid state, it removes material from a solid piece, whether that is raw bar stock or an existing casting, using cutting tools to reach the final shape. CNC machining automates this process, using programmed tool paths to cut, turn, drill, or bore metal to precise tolerances. Comparing CNC vs. casting is not always an either-or question, since CNC machining is often the step that finishes a cast part rather than replacing it.
Casting vs. Machining Applications
When it comes to casting and machining applications, the right process depends on the shape, volume, and industry a part is built for. Centrifugal casting is well suited for hollow, cylindrical components like bearings, sleeves, and pressure vessels, and is widely used in oil and gas, aerospace, marine, and defense applications where large parts and high-performance alloys are common. Machining, on the other hand, is often the better fit for parts with tight tolerances, complex geometries, or smaller production runs, and shows up across industries like automotive, medical devices, and precision tooling. For components that need both strength and precision, though, casting and machining are rarely an either-or decision.
When Casting and Machining Work Together
For many components, the strongest and most cost-effective approach uses both processes. A centrifugally cast blank provides the dense, near-net shape starting point, and CNC machining brings that blank to its exact bore, diameter, and finish. This is the approach Delta Centrifugal® uses across its castings. Parts are offered as cast, rough machined, or finish machined, depending on what a customer’s process requires. This gives manufacturers the strength of centrifugal casting along with the precision of machining, all within a single supply chain.