Die casting shines for complex aluminum or zinc housings, brackets and mounts made in volume. The metal is forced into a hardened tool, so per-part cost falls hard once the tool is paid for. The trap is the tool itself: a design mistake is expensive to undo. This guide covers when casting wins, how tooling cost scales, and how to keep porosity out of the part.
Rough rule: if a part is geometrically complex, made of aluminum or zinc, and you'll need more than a few hundred pieces, casting usually wins. Machining that same shape from billet wastes material and machine time. But for a 20-piece prototype, machining is faster and cheaper because there's no tool to pay for.
If you're unsure which process fits, a supplier-tier and process check up front saves the wrong capital spend. The right answer is often "machine the prototype, cast the production run."
A simple two-cavity aluminum die might run a few thousand dollars; a multi-slide zinc die with cores and inserts costs far more. What you're buying is the tool life and the consistency it delivers. Budget the tool as a project cost, then amortize it across the volume — and confirm who owns the tool (you should) so you're not locked to one shop.
Cast parts fail from trapped gas and shrinkage porosity — rarely visible, always expensive. It shows up as leaks in a pressurized housing or a cracked thread after machining. The controls are process, not luck:
Porosity is managed at the design stage. If a shop only finds it after first articles, the tool is already wrong.
ADC12 is the workhorse die-cast aluminum; A380 and others trade differently on strength and machinability. For the EU, composition and any coating must support compliance and the duty carve-outs. After casting, the part usually needs CNC trimming of the parting line, then machining of sealing faces, then surface finish — anodize or powder.
Planning casting, trimming, machining and finishing as one chain (rather than three vendors) is what keeps a "die-cast housing" on schedule. This is the multi-process coordination that actually moves delivery dates.
Die casting only pays back when the volume is there. Model the tool amortization into unit cost, then add freight and any US Section 232 tariff on the aluminum. Below a real volume threshold, you're better off machining. Above it, casting wins by a wide margin.
I review the tool design before steel is cut, flag porosity risk in the part geometry, and coordinate trimming, machining and finishing in one chain so first articles are right. Send the model; I'll tell you whether to cast or machine, what the tool should cost, and the landed number.
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Send the model and volume — I'll tell you the right process, the tool cost and the landed price.