You need 200 bracket-and-housing sets now, maybe 5,000 next year. The geometry would work in folded sheet metal or an aluminum die casting, and both routes quote within a few hundred dollars of each other for the first batch. This is one of the most common process decisions in low-volume hardware, and picking wrong costs either margin (tooling too early) or schedule (folding parts that should have been cast). Here is how the trade-offs actually line up on the shop floor.
Upfront Economics: Tooling Rules the First Batch
Sheet metal carries no dedicated tooling. A prototype bracket is a laser-cut blank, a couple of punch hits, and two bends; first articles land in days, and revision 2 costs nothing but a program edit. Die casting is the opposite: a simple single-cavity mold for a mid-size housing typically runs $3,000–$15,000 and takes 3–6 weeks before a single part exists. That money is fixed, so it only pays back through volume. Spreading $8,000 of tooling over 200 parts adds $40 per part — usually fatal to a prototype budget. Spread over 10,000 parts it is $0.80, trivial next to the cycle-time savings of a 45–90 second casting cycle.
Geometry: Each Process Has a Comfort Zone
Sheet metal wants constant wall thickness (whatever stock you bought), open profiles, and features reachable by straight bends. It is superb for brackets, chassis plates, EMI shields, and anything that flattens mentally into a 2D outline. It struggles with closed 3D forms — a housing with four walls plus a lid means multiple pieces, welds, and extra finishing labor.
Die casting likes exactly what sheet metal dislikes: variable walls (0.8–4 mm in A380 or ADC12), ribs, bosses, integral standoffs, and complex external geometry in one piece. One cast enclosure often replaces a folded box, four screws, and two welded tabs. The price is draft — typically 1–2° on internal walls — fillets everywhere, and a hard ban on knife edges and sharp corners.
Strength and Consistency
Numbers worth knowing. 5052-H32 sheet yields around 190 MPa with roughly 10% elongation; ADC12 yields about 160–170 MPa but elongates only 1–3% before cracking. In plain language: the sheet part bends before it breaks, the casting does not. For brackets that see overloads or vibration, ductility is real insurance. Castings also carry porosity risk — small voids near cores — which matters for pressure-tight parts and for fatigue life. The folded part answers back with its own quirks: plan on 2°–5° of springback compensation on 90° bends in 5052, and remember bend strength changes with orientation relative to the rolling direction.
Finishing Is Not Equal Either
Both processes take powder coat well, with one trap: die castings can blister during a 180–200 °C cure because gas trapped in the porosity expands. Competent casting sources bake out or vacuum-impregnate parts before finishing, but confirm it in the quote. Anodizing — the default corrosion answer on machined aluminum — turns blotchy on high-silicon casting alloys, so powder coat castings and save anodizing for wrought parts. Sheet metal edges need deburring after laser cutting, but that is routine housekeeping.
A Practical Decision Rule
- Under ~50 parts: fold it or machine it. A thick, simple bracket machined from plate needs zero tooling and holds tight tolerances — our CNC machining services cover one-offs to hundreds this way.
- 50–500 parts: still sheet metal, unless the geometry is truly three-dimensional. This band is where casting tooling rarely amortizes.
- Above roughly 1,000 parts: die casting usually wins on per-part cost, consolidation, and repeatability — our die casting team sizes the mold against your annual volume in the quote.
- Any volume, complex sealed housing: geometry trumps volume. A part you cannot fold is a part you cast or mold, whatever the quantity.
Treat the crossover as a range, not a cliff — part size, wall thickness, and finishing swing it either way — but these bands match how most real quotes shake out.
Design Today So You Can Switch Tomorrow
If you prototype in sheet metal but expect to cast at scale, design for the migration early: keep walls as uniform as the folded design allows, avoid features a mold could not fill, and use standard hole sizes and fastener patterns that map cleanly onto cast bosses later. The reverse works too — start with a casting mindset (draft, fillets, uniform walls) and your prototypes will quote cleaner. And when the product needs real injection-grade plastic enclosures between those worlds, vacuum casting bridges the gap at 20–200 units; see our vacuum casting services for that middle ground.
Neither process is "better." Sheet metal owns the fast, cheap, low-volume middle; die casting owns the consolidated, repeatable, high-volume end. Pick by honest annual volume and geometry, and the choice usually makes itself.
