Casting and machining solve different problems. Casting is efficient at producing complex shapes in volume once tooling exists; machining is efficient at producing precise features without tooling investment, at any volume.
Quick summary: Casting requires upfront tooling investment (a mold or die) but produces complex near-net shapes cheaply at volume. CNC machining requires no tooling and can hold tighter tolerances directly, making it the default for prototypes, low-volume production, and any feature requiring aerospace-grade precision that casting alone can’t deliver.
When Does Casting Make Sense for Aerospace Parts?
At high production volumes, where the upfront tooling cost is justified by a large number of units, and where the part’s tolerance requirements can be met by the casting process itself or with modest machining touch-up.
When Does Machining Make More Sense?
Low-to-moderate volumes, prototypes, or any part where tight tolerances on critical features can’t be reliably achieved through casting alone.
Can the Two Be Combined?
Frequently — a near-net-shape casting is CNC-finished on the specific features that require tight tolerance, combining casting’s volume efficiency with machining’s precision.
What Should Drive the Decision on a New Aerospace Program?
Production volume, tolerance requirements on critical features, and program timeline (casting tooling takes time to develop) should all factor in before committing to one process over the other.
Frequently Asked Questions
Is machining always more precise than casting? Generally yes for tight tolerances, though casting quality varies significantly by process (investment casting vs. sand casting, for example).
Does casting tooling cost make sense for aerospace production volumes? It depends heavily on program volume — many aerospace programs run volumes too low to justify casting tooling, which is why machining dominates in that space.
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Author: Accurate Machine & Tool Team.