Core line, represented 25+ years

Zinc and aluminum die casting

Die casting is a process that injects molten aluminum or zinc into a hardened steel die at high pressure, typically 1,500–25,000 psi (10–170 MPa), to make near-net-shape metal parts with thin walls and fine detail. Because the die is a large upfront cost, die casting becomes economical above roughly 2,500 parts a year.

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Where it pays off

1101001k10k100k1M+

At a glance

Zinc dies last many times longer than aluminum dies, which favors zinc for small, high-volume parts. Aluminum wins on weight and larger sizes.

Linear tolerance: ±0.002–0.010 in (±0.05–0.25 mm) on the first inch, plus about ±0.001 in per added inch (NADCA precision to standard)
Minimum wall: Zinc 0.020–0.040 in (0.5–1.0 mm); aluminum 0.040–0.080 in (1.0–2.0 mm)
Part size: Most parts 0.1–25 lb (0.05–11 kg); machines range 100–4,000+ tons
Draft: Zinc about 0.5–1°; aluminum about 1–2°
As-cast surface finish: Ra about 32–125 µin (0.8–3.2 µm); zinc is smoother than aluminum
Die life: Aluminum about 100,000–150,000 shots; zinc 1,000,000+ shots
Cycle time: Zinc hot-chamber 5–30 seconds; aluminum cold-chamber 30–120 seconds
Common alloys: Aluminum A380, A383, ADC12; zinc Zamak 3, Zamak 5, ZA-8
Tooling cost: $10,000–$100,000+ depending on size, cavities, and slides

Lead time

Tooling: 8–14 weeks
First article: 1–3 weeks after die tryout
Production: 3–6 weeks per release

What would it cost?

The builder's estimator on a representative housing. Change a size, the quantity or the material and the price updates.

All-in price per part (tooling and setup amortized) by order quantity. Budgetary.

Housing · Die casting

$6.81per part, all-in, at 5,000 pcs

Order total $34,062

Tooling: $21,823; one-time, spread over the order
Piece price: $2.33; before setup + tooling
Lead time: 8–12 weeks; to first production

Size

Drag a row to adjust · click to type

Length

140

Width

90.0

Wall

2.20

Material

Design checks pass

Open in builder

Budgetary estimate for a representative part. Firm quotes come from principals after drawing review.

How does it work?

5 steps from drawing to production parts.

1
Die design
Gates, runners, overflows, and vents are laid out, and flow simulation is often run to predict fill and porosity.
2
Die build
Die halves are machined from H13 tool steel, heat treated, and fitted with slides, ejector pins, and cooling lines.
3
Injection
Zinc runs in hot-chamber machines with the injector submerged in the melt. Aluminum is ladled into a cold-chamber shot sleeve and injected each cycle.
4
Solidify and eject
The metal freezes in seconds under pressure. The die opens and ejector pins push the casting out.
5
Trim and finish
A trim die removes gates, overflows, and flash. Parts are then deburred, machined, impregnated, plated, or painted as required.

When is die casting the right call?

Best for

Housings, covers, brackets, and heat sinks
Thin-walled metal parts with complex shapes
Volumes from 2,500 to hundreds of thousands a year
Small, detailed zinc parts that will be plated
Replacing machined or fabricated assemblies with one casting

Pick something else when

Fewer than about 1,000 parts: use CNC machining or sand or investment casting
Highly stressed or weld-critical parts: forging or machined wrought alloy is stronger
Steel or stainless parts: die casting is limited to nonferrous alloys, so consider forging or powdered metal

Materials

3 materials principals run in die casting. Pick one for design rules, finishes and an estimate in that material.

Design rules that keep the price down

Full die casting design guide

Aluminum 0.060–0.150 in (1.5–3.8 mm); zinc 0.040–0.100 in (1.0–2.5 mm)
Keep walls uniform
Thick sections trap shrinkage porosity, and thin ones may not fill.
Aluminum about 1° outside and 2° inside; zinc about 0.5° outside and 1° inside
Add draft
Castings shrink onto cores, so inside walls need more draft to eject cleanly.
Inside radius at least 0.040 in (1 mm)
Radius corners and fillets
Sharp corners slow metal flow, create hot spots, and crack dies.
Rib base about equal to nominal wall
Stiffen with ribs, not mass
Ribs add stiffness without porosity or weight.
Leave 0.010–0.030 in (0.25–0.75 mm) on machined surfaces
Minimize machining stock
The dense skin is near the surface; heavy cuts expose porosity.
Zinc at least 0.040 in (1 mm) diameter; aluminum at least 0.100 in (2.5 mm); depth no more than about 4× diameter
Size cored holes
Small, deep core pins bend, break, and solder to the casting.
Add about ±0.004 in (±0.10 mm) or more across the parting line or slides
Keep critical dimensions in one die half
Die closure and slide movement add variation to dimensions that cross them.
Call out leak test and impregnation per MIL-STD-276 if required
Specify pressure tightness explicitly
Die castings contain some porosity, so leak-tight parts need a defined process.

What drives the cost?

In order of impact.

1
Die cost and complexity
Slides, cores, and cavity count drive die cost. Die cost spread over lifetime volume often decides zinc versus aluminum versus machining.
2
Part weight and alloy
Metal is bought by the pound. Zinc is about 2.4× denser than aluminum, so a zinc part weighs more for the same volume.
3
Machine size
Projected area sets clamp tonnage and the hourly rate. Larger machines also run longer cycles.
4
Secondary machining
Tight bores, threads, and sealing faces are machined after casting. Reducing machined features is often the next-biggest lever after the die.
5
Impregnation, finishing, and scrap
Pressure-tight parts may need vacuum impregnation. Porosity scrap and cosmetic finishes add cost.

Variants

Hot-chamber die casting: The injection system sits in the molten metal, giving fast cycles. Used for zinc and other low-melting alloys.
Cold-chamber die casting: Metal is ladled into a shot sleeve for each cycle. Required for aluminum, which would attack a submerged injector.
Multi-slide zinc die casting: Small zinc parts are cast in compact dies with up to four slides at high rates, often net shape with no trimming.
Vacuum-assisted die casting: Air is evacuated from the cavity before injection to reduce gas porosity in heat-treatable or pressure-tight parts.

Where it shows up

Go deeper

Aluminum die casting guide: A380 vs zinc, draft, walls5 min
A380 aluminum vs Zamak zinc die casting: properties, draft and wall thickness, NADCA tolerances, porosity control, die life, and low-volume alternatives.

Die casting questions

How much does a die casting die cost?

Small, simple zinc dies typically cost $10,000–$25,000. Aluminum dies commonly run $20,000–$100,000, and large dies with multiple slides or cavities can cost more. Size, slides, cavities, and expected shot life set the price.

Is zinc or aluminum better for die casting?

Zinc casts thinner walls, holds tighter tolerances, plates well, and its dies can last 1,000,000 shots or more. Aluminum is about 58% lighter and better for larger parts and heat sinks, but its dies last about 100,000–150,000 shots. Small, detailed, plated parts favor zinc; large or weight-sensitive parts favor aluminum.

What tolerances can die casting hold?

Linear tolerances on the first inch typically range from about ±0.002 in (±0.05 mm) for precision work to ±0.010 in (±0.25 mm) as a standard allowance, plus about ±0.001 in per added inch, following NADCA guidelines. Dimensions across the parting line or slides need extra allowance. Critical bores are usually machined.

What is the minimum order for die cast parts?

Die casting usually needs at least 1,000–2,500 parts a year to pay back the die. For lower volumes, CNC machining, sand casting, or investment casting is usually cheaper.

Are die castings pressure tight?

Die castings contain some gas and shrinkage porosity, so leak-tight parts often need vacuum impregnation after machining. Good gating, vacuum assist, and uniform walls reduce porosity at the source.

How long does die casting tooling take?

Die builds typically take 8–14 weeks, followed by sampling and first article approval in 1–3 weeks. Production releases usually ship 3–6 weeks after order.

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Zinc and aluminum die casting

Where it pays off

1101001k10k100k1M+